Abstract:
A series of herbicidal molecules derived from 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone, a natural substance, and their potential use in agriculture for weed control. Through the modification of the 5-sec-butyl hydrocarbon chain and 3-acetyl group and the analysis of their biological functioning, newly designed molecules are superior to the original compound in herbicidal activity. These molecules inhibit the photosynthesis of the plants. The treated plants show significant damage in 24 hours and die within 3-5 days after the chemical treatment. In addition, the new molecule has relatively simple structure, they are easy to make and they have better physical properties. They are broad-spectrum, high potency herbicides.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of International Patent Application No. PCT/CN2006/001315 with an international filing date of Jun. 13, 2006, designating the United States, now pending, and further claims priority benefits to Chinese Patent Application No. 200510094521.9 filed Sep. 26, 2005. The contents of the aforementioned specifications are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of Invention 
         [0003]    This invention relates to the application of chemicals and biochemicals to weed control in agriculture and, more specifically to pyrrolidineone derivatives of herbicidal tenuazonic acid (3-acetyl-4-hydroxy-5-tert-butylpyrroline-2-ketone), and to their use as herbicides. 
         [0004]    2. Description of the Related Art 
         [0005]    Tenuazonic acid (formula name: 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone) is a strong phytotoxin, isolated, purified and identified from metabolites of  Alternaria Alternata  by Qiang Sheng et al. It is isolated from the crude mixture of metabolites by the extraction of the fermentation fluid. Due to the low yield (0.0005%) and high cost of fermentation, it is very important to develop a synthetic process. Through a rational design, more potent compounds can be made that are also easy to manufacture. Environmentally safe herbicides can be developed with low toxicity. This is the main direction of the current herbicide development. 
         [0006]    3-Acetyl-4-hydroxy-5-tert-butylpyrroline-2-ketone is a heterocyclic compound containing carbonyl and hydroxyl functional groups. The lactam that is part of the heterocyclic ring is the most important functional group. The hydrophobic side chain also plays an important role in its herbicidal activity. 
         [0007]    The compound is very effective at killing monocotyledon weeds (such as common crabgrass and barnyardgrass) and dicotyledonous weeds including Crofton weeds at a concentration of 50 μg/mL. It has the potential to become a biological herbicide (CN Pat. Appl. No. 200510038263.2; CN Pat. No. 1644046. However, the low yield and high cost associated with the fermentation process prevents large-scale production of this compound. 
         [0008]    A1994 patent (WO1994/01401) discloses 3-benzoylpyrrolidine-2,4-dione derivatives and their herbicidal activity. 
         [0009]    Chinese Pat. No. 1676515A made claims based on the fact that some triketones inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD), which is a key enzyme responsible for biosynthesis of plastoquinone and α-tocopherol. If the biosynthesis of plastoquinone and α-tocopherol is blocked, it will impact the biosynthesis of carotenoids. Therefore both HPPD inhibitor and carotenoid preventing inhibitors have similar function. Taking advantage of similar structural modification and synthesis, a key characteristic of this type of compounds is the existence of N-substituent. The major representative of this type of herbicides is sulfentrazone, including isoxazole herbicide, and pyridine type herbicides. It is reported that tenuazonic acid copper salt has a slight inhibition to HPPD (Meazza et al., 2002). With only hydrogen attached to nitrogen, no other substituents, it is obvious that 3-acetyl-4-hydroxy-5-tert-butylpyrroline-2-ketone has a totally different mechanism of action. 
         [0010]    Study on the mechanism of action of 3-acetyl-4-hydroxy-5-tert-butylpyrroline-2-ketone has shown that the phytotoxin clearly inhibits plant&#39;s photosynthesis. Its inhibition to Hill reaction is much higher than the typical photosynthetic inhibitor (herbicide), such as 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU). In addition, there is no adverse effect to other parts of the cells. The compound blocks electron flow from Q A  to Q B  in the photosystem II, but has no effect on the donor of photosystem II, photosystem I and other parts of chloroplasts, which was the first time such effects were observed among known phytotoxins produced by fungus  Alternaria alternata.    
         [0011]    It is believed that the toxin interacts with D1 protein by competing with Q B  for the binding site and thus inhibits the electron transfer. Therefore, it is an inhibitory phytotoxin of photosystem II. Based on the discovery of this mechanism, the molecular structure of tenuazonic acid has heretofore been and new herbicidal molecules discovered. CN Appl. Nos. 200510094521.9 and 200610038765.X, and CN Pat Pub No CN1752075 disclose certain compounds and methods of their synthesis. 
         [0012]    Many photosystem II inhibitors have successfully become commercial herbicides, such as s-triazines, triazinones and phenols, etc., and have become major players in the field of herbicides. There are two advantages associated with photosystem II inhibitors: first, since photosynthesis is a common phenomenon among plants, and inhibition is specific to the plants, the toxicity to animals is low, thus this type of herbicides possesses the characteristics of high efficacy and low toxicity. Secondly, with the development of transgenic technology, there are 67,700,000 hectares of farm land that grow transgenic crops globally and greater than 80% of these crops are herbicide-resistant transgenic (based on Monsanto&#39;s 2003 data). 
         [0013]    The photosynthetic inhibitors herbicides have a growing share of the herbicides market. With combination of new herbicides and transgenic agricultural products, the chemical pollution to the environment has been greatly reduced. Since the photosynthetic inhibition is the only effect for 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone on the plant cells, this type of herbicide with high potency, quick action, broad-spectrum, simple structure and easy synthesis will have a bright future. 
         [0014]    There are many types of photosystem II inhibitors according to their chemical structures such as ureas, pyridines, triazinones, pyridazinones, dinitrophenols and cyanophenols, etc. They can be divided into two main groups such as ureas/triazine and phenol. The first type (classical photosystem II inhibitors) can be represented as N—C═X (X stands for O or N atom, not sulfur atom), i.e. atrazine, metribuzin, phemedipham, terbutryand, N-(3,4-dichlorophenyl)-N′-methylurea (DCMU) et al. The second type is phenolic herbicide, including ioxynil, dinoseb and 2-iodo-4-nitro-6-isobutylphenol, etc. 
         [0015]    The common feature of the second type of herbicide is that the molecules contain at least one carbonyl oxygen, or a hydroxy oxygen and a long hydrophobic hydrocarbon side-chain. Most of these herbicides form a hydrogen bond between the carbonyl hydrogen and the D1 protein of photosystem II, which enables them to successfully compete with plastoquinone Q B  (secondary electron acceptor), thus block electron transfer from Q A  to Q B , and lead to the inhibition of photosynthetic process of the plant. 
         [0016]    Only a small number of herbicides form hydrogen bond between hydroxyl oxygen and D1 protein and successfully blocking photosynthetic process. The structure of the hydrophobic hydrocarbon side-chain (number of carbon and chain length) also influences herbicidal activity. Obviously, the binding site, binding manner and possible binding region of herbicides to D1 protein determines the strength of herbicidal activity. Based on the chemical structure, 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone belongs to the group of photosystem II inhibitor (containing N—C═O). Unlike the classical herbicides mentioned earlier, there are no literature reports that describe the mechanism of action of this compound to photosynthesis. Therefore, it might be a new type of photosystem II inhibitor. 
         [0017]    3-Acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone has moderate toxicity of 200 mg/kg to rat and moderate level phytotoxicity, which is acceptable in light of its high biological activity. However, its toxicity level may be reduced through modification of its chemical structure. 
       SUMMARY OF THE INVENTION 
       [0018]    In one embodiment, the invention is directed to compounds represented by the general formula (I), or (II), or a salt thereof 
         [0000]    
       
                 
         
             
             
         
       
     
         [0019]    In a class of this embodiment, R 1  independently and at each occurrence represents H; or —C k H 2k+1 , —OC k H 2k+1 , —(C═O)C k H 2k+1 , —COOC k H 2+1 , —C k H 2k−1 , —OC k H 2k−1 , —(C═O)C k H 2k−1 , or —COOC k H 2k−1 , each unsubstituted or substituted by one or more substituents selected from a heterocycle, an aryl, a phenylalkyl, a heterocycloalkyl phenyl, a heterocycloalkyl, a heterocycloalkoxyl, a phenoxyl; a phenoxy phenyl; a halogen, a cyano, a nitro, an alkoxyalkyl, an alkoxycarbonyl, and/or an amido. 
         [0020]    In another class of this embodiment, R 2 , and R 3  each independently and at each occurrence represent H, C n H 2n+1 , C n H 2n−1 , a halogen, —CN, a phenyl, a halogenated alkyl, a cyano-alkyl, a phenylalkyl, a halogenoalkenyl, a cyanoalkenyl, or a phenylalkenyl. 
         [0021]    In another class of this embodiment, R 2  and R 3  each independently and at each occurrence represent H, —CH 3 , —C 2 H 5 , —CH 2 CH 2 CH 3 , —CH(CH 3 ) 2 , —(CH 2 ) 3 CH 3 , —C(CH 3 ) 3 , —CH 2 CH(CH 3 )CH 3 , —CH(CH 3 )CH 2 CH 3 , —(CH 2 ) 4 CH 3 , —CH(CH 3 )CH 2 CH 2 CH 3 , —CH 2 CH(CH 3 )CH 2 CH 3 , —CH 2 CH 2 CH(CH 3 ) 2 , —CH(CH 2 CH 3 ) 2 , —C(CH 2 ) 2 C 2 H 5 , —(CH 2 ) 5 CH 3 , —CH(CH 3 )(CH 2 ) 3 CH 3 , —CH 2 CH(CH 3 )(CH 2 ) 2 CH 3 , —CH 2 CH 2 CH(CH 3 )CH 2 CH 3 , —(CH 2 ) 3 CH(CH 3 ) 2 , —CH(CH 2 CH 3 )CH 2 CH 2 CH 3 , —CH 2 CH(CH 2 CH 3 ) 2 , —C(CH 3 ) 2 (CH 2 ) 2 CH 3 , —C(CH 3 )CH 2 CH 3 ) 2 , —(CH 2 ) 6 CH 3 , —CH(CH 2 CH 2 CH 3 ) 2 , —CH 2 CH 2 CH(CH 2 CH 3 ) 2 , —CH(CH 2 CH 3 )(CH 2 ) 3 CH 3 , —CH 2 CH(CH 2 CH 3 )CH 2 CH 2 CH 3 , —CH(CH 3 )(CH 2 ) 4 CH 3 , —CH 2 CH(CH 3 )(CH 2 ) 3 CH 3 , —(CH 2 ) 2 CH(CH 3 )(CH 2 ) 2 CH 3 , —(CH 2 ) 3 CH(CH 3 )CH 2 CH 3 , —(CH 2 ) 7 CH 3 , —CH 2 CH(CH 2 CH 2 CH 3 ) 2 , —CH(CH 2 CH 2 CH 3 )(CH 2 ) 3 CH 3 , —CH(CH 3 )(CH 2 ) 5 CH 3 , —CH 2 CH(CH 3 )(CH 2 ) 4 CH 3 , —(CH 2 ) 2 CH(CH 3 )(CH 2 ) 3 CH 3 , —(CH 2 ) 3 CH(CH 3 )(CH 2 ) 2 CH 3 , —(CH 2 ) 4 CH(CH 3 )CH 2 CH 3 , —CH(CH 2 CH 3 )(CH 2 ) 4 CH 3 , —(CH 2 ) 3 CH(CH 2 CH 3 ) 2 , —CH 2 CH(CH 2 CH 3 )(CH 2 ) 3 CH 3 , —(CH 2 ) 2 CH(CH 2 CH 3 )(CH 2 ) 2 CH 3 , —CH═CH 2 , —CH═CHCH 3 , —CH 2 CH═CH 2 , —CH═CHCH 2 CH 3 , —CH 2 CH 2 CH═CH 2 , —CH 2  CH═CHCH 3 , or —CH═CH—CH═CH 2 . 
         [0022]    In another class of this embodiment, R 2  and R 3  each independently and at each occurrence represent —CN or a phenyl group substituted at positions 1-3 by a substituent selected from: —CHClCH 3 , —CHClCH 2 CH 3 , —CHClC 3 H 7 , —CHClC 4 H 9 , —CHClC 5 H 11 , —CHClC 6 H 13 , —CHClC 7 H 15 , —CHFCH 3 , —CHFCH 2 CH 3 , —CHFC 3 H 7 , —CHFC 4 H 9 , —CHFC 5 H 11 , —CHFC 6 H 13 , —CHFC 7 H 15 , —CHCNCH 3 , —CHCNCH 2 CH 3 , —CHCNC 3 H 7 , —CHCNC 4 H 9 , —CHCNC 5 H 11 , —CHCNC 6 H 13 , —CHCNC 7 H 15 , —CH(C 6 H 5 )CH 3 , —CH(C 6 H 5 )CH 2 CH 3 , —CH(C 6 H 5 )C 3 H 7 , —CH(C 6 H 5 )C 4 H 9 , —CH(C 6 H 5 )C 5 H 11 , —CH(C 6 H 5 )C 6 H 13 , —CH(C 6 H 5 )C 7 H 15 , —CHClCH═CH 2 , or —CHClCH 2 CH═CH 2 , or a corresponding isomeric halogenate. 
         [0023]    In another class of this embodiment, X is CN, a C 1  to C 5  amido, a benzyl, a naphthalenyl, a phenyl, a pyrrolyl, a furyl, a thiazolyl, a heterocyclic alkyl phenyl; each phenyl or heterocycle being unsubstituted or substituted by a substituent selected from a C 1  to C 6  alkyl, a C 1  to C 4  alkoxy, a halogenated C 1  to C 5  alkyl, a halogen, a C 1  to C 5  amido, a nitro, a cyano, an alkoxycarbonyl, and/or a C 1  to C 5  sulfonyl group. 
         [0024]    In another class of this embodiment, the compounds are calcium, magnesium, copper, iron, nickel, sodium, potassium, magnesium, zinc or ammonium salts. 
         [0025]    In another class of this embodiment, k represents an integer from 1 to 8. 
         [0026]    In another class of this embodiment, n represent an integer from 1 to 15. 
         [0027]    In another embodiment, the invention is directed to compounds represented by the general formula (III), (IV) or (V) 
         [0000]    
       
                 
         
             
             
         
       
     
         [0028]    In a class of this embodiment, X independently and at each occurrence represents H; or —C m H 2m+1 , or —OC m H 2m+ , each unsubstituted or substituted by one or more substituents selected from a heterocyclic alkyl, a heterocyclic aryl, an aryl, a phenylalkyl, a heterocycloalkyl phenyl, a heterocycloalkyl, a heterocycloalkoxyl, a phenoxyl; a phenoxy phenyl; a halogen, a cyano, a nitro, an alkoxyalkyl, an alkoxycarbonyl, and/or an amido. 
         [0029]    In another class of this embodiment, R 2  and R 3  each independently and at each occurrence represents H, C n H 2n+1 , C n H 2n−1 , a halogen, —CN, a phenyl, a halogenated alkyl, a cyano-alkyl, a phenylalkyl, a halogenoalkenyl, a cyanoalkenyl, or a phenylalkenyl. 
         [0030]    In another class of this embodiment, m represents an integer from 1 to 7. 
         [0031]    In other aspects, the invention is directed to a method for preparation of a compound of claim  1  comprising the following steps:
       (a) reacting an aminoacid of formula:       
 
         [0000]    
       
                 
         
             
             
         
       
     
         [0033]    with an alcohol under acidic reaction conditions;
       (b) neutralizing with sodium ethoxide; and   (c) adding a compound of formula XCOCH 2 COY or cyclobutane-1,3-dione in the presence of a sodium alkoxide.       
 
         [0036]    In a class of this embodiment, X independently and at each occurrence represents H; or —C m H 2m+1 , or —OC m H 2m+1 , each unsubstituted or substituted by one or more substituents selected from a heterocyclic alkyl, a heterocyclic aryl, an aryl, a phenylalkyl, a heterocycloalkyl phenyl, a heterocycloalkyl, a heterocycloalkoxyl, a phenoxyl; a phenoxy phenyl; a halogen, a cyano, a nitro, an alkoxyalkyl, an alkoxycarbonyl, and/or an amido. 
         [0037]    In another class of this embodiment, m represents an integer from 1 to 7. 
         [0038]    In another class of this embodiment, Y is Cl or Br. 
         [0039]    In another class of this embodiment, the steps are carried out in situ without purification of intermediates. 
         [0040]    In other aspects, the invention is directed to a method of eradicating weeds, comprising applying to the weeds compounds described herein. 
         [0041]    In a class of this embodiment, the compound is applied in a solution having a concentration of between 10 and 800 μg of the compound per 1 g of the solution. 
         [0042]    In another class of this embodiment, the weeds are broadleaf plants, grassy weeds, or sedge weeds. 
         [0043]    In another class of this embodiment, the compound is applied under exposure to sun light. 
         [0044]    In another class of this embodiment, the compound inhibits photosynthesis and metabolism of the plant cell, which causes a rapid accumulation of large amounts of reactive oxygen species in cells of the weeds and subsequent death of the cells. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0045]    This invention provides a pyrrolidineone-type herbicide, which was developed through a modification of tenuazonic acid, a patented herbicidal compound (chemical name: 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone). The modification provided us a quick and effective way of developing the new herbicides. 
         [0046]    It was decided to keep the major functional carbonyl group of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone and modify the hydrophobic 5-sec-butyl chain and the 3-acetyl group. A large number of derivatives were synthesized using phosphorous ylides and halogenated amino acids as precursors. Recently, a new synthetic route was developed, which no longer uses phosphor ylides and halogenated amino acids as starting materials. The new process starts from an amino acid and the 4 step reaction sequence is carried out in one pot without isolation and purification of any intermediates. 
         [0047]    The synthetic pathway is as follows: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0048]    wherein 
         [0049]    X═H; —C m H 2m+1  substituted or unsubstituted; —OC m H 2m+1  substituted or unsubstituted; —C m H 2m−1  substituted or unsubstituted, —OC m H 2m−1  substituted or unsubstituted; a substituted heterocyclic, an aryl, a phenylalkyl, a heterocycloalkyl-phenyl, a heterocycloalkyl, a heterocycloalkoxy, a phenoxy, or a phenoxyphenyl; the substituent groups being a halogen, a cyano, a nitro, an alkyoxyalkyl, an alkyoxycarbonyl, and/or an amido; 
         [0050]    m represents from 1 to 7 carbon atoms; and 
         [0051]    R 2 , and R 3  each independently and at each occurrence represent H, —CH 3 , —C 2 H 5 , —CH 2 CH 2 CH 3 , —CH(CH 3 ) 2 , —(CH 2 ) 3 CH 3 , —C(CH 3 ) 3 , —CH 2 CH(CH 3 )CH 3 , —CH(CH 3 )CH 2 CH 3 , —(CH 2 ) 4 CH 3 , —CH(CH 3 )CH 2 CH 2 CH 3 , —CH 2 CH(CH 3 )CH 2 CH 3 , —CH 2 CH 2 CH(CH 3 ) 2 , —CH(CH 2 CH 3 ) 2 , —C(CH 2 ) 2 C 2 H 5 , —(CH 2 ) 5 CH 3 , —CH(CH 3 )(CH 2 ) 3 CH 3 , —CH 2 CH(CH 3 )(CH 2 ) 2 CH 3 , —CH 2 CH 2 CH(CH 3 )CH 2 CH 3 , —(CH 2 ) 3 CH(CH 3 ) 2 , —CH(CH 2 CH 3 )CH 2 CH 2 CH 3 , —CH 2 CH(CH 2 CH 3 ) 2 , —C(CH 3 ) 2 (CH 2 ) 2 CH 3 , —C(CH 3 )CH 2 CH 3 ) 2 , —(CH 2 ) 6 CH 3 , —CH(CH 2 CH 2 CH 3 ) 2 , —CH 2 CH 2 CH(CH 2 CH 3 ) 2 , —CH(CH 2 CH 3 )(CH 2 ) 3 CH 3 , —CH 2 CH(CH 2 CH 3 )CH 2 CH 2 CH 3 , —CH(CH 3 )(CH 2 ) 4 CH 3 , —CH 2 CH(CH 3 )(CH 2 ) 3 CH 3 , —(CH 2 ) 2 CH(CH 3 )(CH 2 ) 2 CH 3 , —(CH 2 ) 3 CH(CH 3 )CH 2 CH 3 , —(CH 2 ) 7 CH 3 , —CH 2 CH(CH 2 CH 2 CH 3 ) 2 , —CH(CH 2 CH 2 CH 3 )(CH 2 ) 3 CH 3 , —CH(CH 3 )(CH 2 ) 5 CH 3 , —CH 2 CH(CH 3 )(CH 2 ) 4 CH 3 , —(CH 2 ) 2 CH(CH 3 )(CH 2 ) 3 CH 3 , —(CH 2 ) 3 CH(CH 3 )(CH 2 ) 2 CH 3 , —(CH 2 ) 4 CH(CH 3 )CH 2 CH 3 , —CH(CH 2 CH 3 )(CH 2 ) 4 CH 3 , —(CH 2 ) 3 CH(CH 2 CH 3 ) 2 , —CH 2 CH(CH 2 CH 3 )(CH 2 ) 3 CH 3 , —(CH 2 ) 2 CH(CH 2 CH 3 )(CH 2 ) 2 CH 3 , —CH═CH 2 , —CH═CHCH 3 , —CH 2 CH═CH 2 , —CH═CHCH 2 CH 3 , —CH 2 CH 2 CH═CH 2 , —CH 2  CH═CHCH 3 , —CH═CH—CH═CH 2 , —CN, phenyl, —CHClCH 3 , —CHClCH 2 CH 3 , —CHClC 3 H 7 , —CHClC 4 H 9 , —CHClC 5 H 11 , —CHClC 6 H 13 , —CHClC 7 H 15 , —CHFCH 3 , —CHFCH 2 CH 3 , —CHFC 3 H 7 , —CHFC 4 H 9 , —CHFC 5 H 11 , —CHFC 6 H 13 , —CHFC 7 H 15 , —CHCNCH 3 , —CHCNCH 2 CH 3 , —CHCNC 3 H 7 , —CHCNC 4 H 9 , —CHCNC 5 H 11 , —CHCNC 6 H 13 , —CHCNC 7 H 15 , —CH(C 6 H 5 )CH 3 , —CH(C 6 H 5 )CH 2 CH 3 , —CH(C 6 H 5 )C 3 H 7 , —CH(C 6 H 5 )C 4 H 9 , —CH(C 6 H 5 )C 5 H 11 , —CH(C 6 H 5 )C 6 H 13 , —CH(C 6 H 5 )C 7 H 15 , —CHClCH═CH 2 , or —CHClCH 2 CH═CH 2 . 
         [0052]    When X is a methyl group, the following synthetic method can also be used: 
         [0000]    
       
                 
         
             
             
         
       
     
         [0053]    3-Acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone analogs were dissolved in a small amount of methanol and diluted with water to a concentration of 5-100 μg/g. A pathogenic test was conducted by placing the toxic liquid on the slightly wounded leaf of Crofton weed with a needle. The test has shown that the pathogenic capability of 3-Acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone analogs with respect to Crofton weed increases with the increase of concentration. The spot diameter caused on the leaf of Crofton weed after 24 hours was 2 mm at 50 μg/g. 
         [0054]    The mechanism of action of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone analogs on weeds is the effect on plant photosynthesis; significantly reducing the photosynthetic oxygen evolution rate and the apparent quantum efficiency. The main action site of the compounds is the thylakoid membrane, inhibiting the electron transfer reaction of two photosystems, especially photosystem II, but no effect has been observed on the structure and synthesis of the membrane protein. In addition, the active oxygen content significantly increased 3 hours after the leaf was treated with 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone analogs. This may be the cause of cell death and appearance of the brown spots on the leaf. Moreover, it may also block the synthesis of protein in the ribosome. 
         [0055]    The main advantages and positive effects of the invention include: modification of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone was carried out, based on (1): its inhibitory activity to photosystem II and its binding mode to D1 protein; and (2): its inhibitory activity and its action sites, combined with chemical synthetic route of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone. Focus was placed on the carbonyl oxygen (a few hydroxyl oxygens), which played essential role in the protein binding. The structure of D1 protein from algae was carefully analyzed and of various factors including hydrophobicity, electronegativity and stereo hindrance were considered when designing and selecting the target molecules. It is obvious that such rational design has advantage over the traditional chemical herbicide screening. 
         [0056]    A series of herbicidal molecules was prepared through the modification of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone, a metabolic phytotoxin of  Alternaria alternata . These compounds kill weeds quickly; the weeds treated with the herbicidal agents clearly show symptoms after 24 hours, and the weeds can be killed in about 3 to 5 days. 
         [0057]    The method of biocontrolling weeds using the analogues of tenuazonic acid and their salts effectively controls and eradicates the main gramineous weeds in the farmland, such as common crabgrass, barnyardgrass, goosegrass, green foxtail, equal alopecurus, Japanese alopecurus, Beckmannia syzigachne Fern, wild oat, annual bluegrass, keng stiffgrass, common polypogon, and rabbitfoot polypogon; broad leaf weeds, such as Crofton weed, Copperleaf, Yerbadetajo, Redroot pigweed, Tender catchweed bedstraw, Narrowleaf vetch, Sheathed monochoria, Indian rotala, Water ammannia, Purslane, Flixweed tansymustard, Shepherdspurse, Common dayflower, Wild cress, Wormseed mustard, Pennsylvania bittercress, Geminate speedwell, Mouse-ear chickweed; and sedges, such as Needle spikesedge, Difformed galingale, Rice galingale, and Dichotomous dimbristylis. 
         [0058]    The compounds of the invention have high activity at concentration as low as from 5 to 50 μg/g. At a concentration of 10 to 800 μg/g (close to 45-360 g/hectare), the compounds can kill a variety of broad-leaf weeds, grassy weeds and sedge weeds. They are highly potential herbicides. 
         [0059]    The analogues disclosed herein have comparable herbicidal activity to the original tenuazonic acid. These molecules are easy to make, thus reducing the manufacturing cost. Because these compounds were obtained through modification of the metabolite of a fungus, a natural product, these analogs have some desirable characteristics of bio-based herbicides: low pollution, few byproducts, high rate of decomposition and high environmental safety. 
         [0060]    The new synthetic process can be carried out in one pot without isolation and purification of the intermediates. This process can reduce the manufacturing cost. 
       EXAMPLES 
       [0061]    The following examples illustrate the products of this invention and the methods for preparing them. However, the examples are not intended in any way to otherwise limit the scope of the invention. The number of compounds that were synthesized and evaluated is far exceeding the number of examples. 
       Example 1 
       [0062]    List of compounds having formula (I) and (II) (Table 1) and their herbicidal activities (Table 2). 
         [0063]    Synthesis of compound 1: A 100 mL three-neck flask was charged with anhydrous alcohol (30 mL), hydrogen chloride (0.055 mol, 2 g) and Isoleucine (0.05 mol, 6.56 g). The mixture was heated to reflux and stirred for 3 h and then left overnight. Ethanol was removed by distillation and the residue was mixed with sodium ethoxide (0.05 mol, 2.6 g, freshly prepared) solution in ethanol. The mixture was stirred for 0.5 h. Cyclobutane-1,3-dione (0.055 mol, 4.62 g) was added over 1 h, with the temperature kept below 10° C., and the reaction was stirred for 2 h. Benzene (20 ml) and sodium ethoxide (0.0575 mol, 3 g, freshly prepared) solution in ethanol were added, and the mixture was stirred at reflux for 3 h and allowed to stand at room temperature overnight. The reaction mixture was poured into 30 mL of water and acidified with 10% sulfuric acid (0.055 mol, 55 g), then extracted with ethyl acetate and dried over sodium sulfate. Ethyl acetate was removed under vacuum and the residue was mixed with concentrated sulfuric acid and toluene. The mixture was refluxed in toluene for 2 h. Compound 1 was obtained as a brown solid after column chromatography in a 55.6% yield. 
         [0064]    Synthesis of compound 9: A 100 mL three-neck flask was charged with anhydrous alcohol (30 mL), hydrogen chloride (0.055 mol, 2 g) and Isoleucine (0.05 mol, 6.56 g). The mixture was heated to reflux and stirred for 3 h and then left overnight. Ethanol was removed by distillation and the residue was mixed with sodium ethoxide (0.05 mol, 2.6 g, freshly prepared) solution in ethanol and stirred for 0.5 h. 2-Propionamidoacetyl chloride (0.055 mol, 8.22 g) was added over 1 h and the reaction was stirred for 2 h. Benzene (20 ml) and sodium ethoxide (0.0575 mol, 3 g, freshly prepared) solutions were added, and the mixture was stirred at reflux for 3 h and allowed to stand at room temperature overnight. The reaction mixture was poured into 30 mL of water and acidified with 10% sulfuric acid (0.055 mol, 55 g), then extracted with ethyl acetate and dried over sodium sulfate. Removal of ethyl acetate under vacuum gave crude product which was purified with column chromatography, providing compound 9 as a pale brown oil in a 47.1% yield. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Physical properties of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone 
               
               
                 analogs with formula (I) and (II) 
               
             
          
           
               
                 Com- 
                   
                   
                   
                   
                   
               
               
                 pound 
                 Type 
                 R 1   
                 R 2   
                 R 3   
                 Appearance 
               
               
                   
               
               
                 1 
                 II 
                 H 
                 sec-C 4 H 9   
                 H 
                 Brown solid 
               
               
                 2 
                 II 
                 H 
                 C 3 H 7 CHCl 
                 H 
                 Brown solid 
               
               
                 3 
                 I 
                 H 
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 4 
                 I 
                 CH 3 CH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 5 
                 I 
                 C 2 H 5 O 
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 6 
                 I 
                 C 6 H 5 CH 2 CH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 7 
                 I 
                 NH 2 COCH 3 CH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 8 
                 I 
                 Cl(CH 2 ) 3 NH 
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 9 
                 I 
                 C 2 H 5 CONH 
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Comparison of the toxicity of 3-acetyl-4-hydroxy-5-sec- 
               
               
                 butylpyrroline-2-ketone analogs with formula (I) and (II) 
               
             
          
           
               
                   
                 Time of disease spot 
                 Average diameter of 
               
               
                 Treatment 
                 to occur (h) 
                 the spot after 24 h (mm) 
               
               
                   
               
               
                 Water control 
                 / 
                 0.23 ± 0.02 
               
               
                 Methanol 
                 / 
                 0.27 ± 0.14 
               
               
                 control 
               
               
                 1 
                 22.3 ± 0.77 
                 1.97 ± 0.04 
               
               
                 2 
                 22.0 ± 2.30 
                 2.96 ± 0.01 
               
               
                 3 
                 20.9 ± 1.01 
                 2.31 ± 0.09 
               
               
                 4 
                 18.5 ± 1.55 
                 2.97 ± 0.01 
               
               
                 5 
                 20.7 ± 0.75 
                 2.35 ± 0.14 
               
               
                 6 
                 21.2 ± 3.85 
                 2.12 ± 0.08 
               
               
                 7 
                 14.9 ± 2.65 
                 4.45 ± 0.22 
               
               
                 8 
                 20.0 ± 1.51 
                 2.53 ± 0.18 
               
               
                 9 
                 21.9 ± 2.00 
                 2.80 ± 0.33 
               
               
                   
               
             
          
         
       
     
       Example 2 
       [0065]    Herbicidal activity evaluation of compounds 10-57 with formula (III), (IV) and (V) (Table 3). 
         [0066]    Synthesis of compound 24: A100 mL three-neck flask was charged with anhydrous alcohol (30 mL), hydrogen chloride (0.055 mol, 2 g) and 2-amino-2-methylbutanoic acid (0.05 mol, 5.85 g). The mixture was heated to reflux and stirred for 3 h and then left for overnight. Ethanol was removed by distillation and the residue was mixed with sodium ethoxide (0.05 mol, 2.6 g, freshly prepared) solution in ethanol and stirred for 0.5 h. Cyclobutane-1,3-dione (0.055 mol, 4.62 g) was added over 1 h maintaining the temperature of the reaction mixture below 10° C., and the reaction was stirred for 2 h. Benzene (20 ml) and sodium ethoxide (0.0575 mol, 3 g, freshly prepared) solution in ethanol were added, and the mixture was stirred at reflux and then allowed to stand for 3 h at room temperature overnight. The reaction mixture was mixed with 30 mL of water and acidified with 10% sulfuric acid (0.055 mol, 55 g), then extracted with ethyl acetate and dried over sodium sulfate. Removal of ethyl acetate under vacuum gave crude product, which was purified with column chromatography, providing compound 24 as a pale brown oil in a 53% yield. 
         [0067]    Synthesis of Compound 53: A 100 mL of three-neck flask was charged with anhydrous alcohol (30 mL), hydrogen chloride (0.055 mol, 2 g) and 2-amino-3-cyanohexanoic acid (0.05 mol, 7.81 g). The mixture was heated to reflux and stirred for 3 h and then left overnight. Ethanol was removed by distillation and the residue was mixed with sodium ethoxide (0.05 mol, 2.6 g, freshly prepared) solution in ethanol, and stirred for 0.5 h. Cyclobutane-1,3-dione (0.055 mol, 4.62 g) was added over 1 h and maintaining the temperature of the reaction mixture below 10° C., and the reaction was stirred for 2 h. Benzene (20 mL) and sodium ethoxide (0.0575 mol, 3 g, freshly prepared) solution in ethanol were added, and the mixture was stirred at reflux for 3 h and then to allowed to stand at room temperature overnight. The reaction mixture was mixed with 30 mL of water and acidified with 10% sulfuric acid (0.055 mol, 55 g), extracted with ethyl acetate and dried over sodium sulfate. Removal of ethyl acetate under vacuum gave crude product, which was purified with column chromatography, providing compound 53 as a brown oil in 45% yield. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 3 
               
             
             
               
                   
               
               
                 Physical properties of 3-Acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone 
               
               
                 analogues with formula of (III), (IV) and (V). 
               
             
          
           
               
                 Com- 
                   
                   
                   
                   
                   
               
               
                 pound 
                 Type 
                 X 
                 R 2   
                 R 3   
                 Appearance 
               
               
                   
               
             
          
           
               
                 10 
                 III 
                 CH 3   
                 H 
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 11 
                 III 
                 CH 3   
                 CH 3   
                 H 
                 Pale needle 
               
               
                   
                   
                   
                   
                   
                 crystal 
               
               
                 12 
                 III 
                 CH 3   
                 CH 3 CH 2   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 13 
                 III 
                 CH 3   
                 CH 3 CH 2 CH 2   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 14 
                 III 
                 CH 3   
                 n-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 15 
                 III 
                 CH 3   
                 n-C 5 H 11   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 16 
                 III 
                 CH 3   
                 n-C 6 H 13   
                 H 
                 Light brown oil 
               
               
                 17 
                 III 
                 CH 3   
                 n-C 7 H 15   
                 H 
                 Light brown oil 
               
               
                 18 
                 III 
                 CH 3   
                 n-C 8 H 17   
                 H 
                 Light brown oil 
               
               
                 19 
                 III 
                 CH 3   
                 C 6 H 5 CH 2   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 20 
                 III 
                 CH 3   
                 (1-C 6 H 5 )C 4 H 8   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 21 
                 III 
                 CH 3   
                 H 3 C—CH:CH 
                 H 
                 Brown viscous 
               
               
                   
                   
                   
                   
                   
                 liquid 
               
               
                 22 
                 III 
                 CH 3   
                 CH 3   
                 CH 3   
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 23 
                 III 
                 CH 3   
                 CH 3 CH 2   
                 CH 3 CH 2   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 24 
                 III 
                 CH 3   
                 CH 3 CH 2   
                 CH 3   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 25 
                 III 
                 CH 3   
                 CH 3 CH 2 CH 2   
                 CH 3 CH 2 CH 2   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 26 
                 III 
                 CH 3   
                 CH 3 CH 2 CH 2   
                 CH 3   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 27 
                 III 
                 CH 3   
                 CH 3 CH 2 CH 2   
                 CH 3 CH 2   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 28 
                 III 
                 CH 3   
                 n-C 4 H 9   
                 n-C 4 H 9   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 29 
                 III 
                 CH 3   
                 n-C 4 H 9   
                 CH 3   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 30 
                 III 
                 CH 3   
                 n-C 4 H 9   
                 CH 3 CH 2   
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 31 
                 III 
                 CH 3   
                 sec-C 5 H 11   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 liquid 
               
               
                 32 
                 III 
                 CH 3   
                 tert-C 5 H 11   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 liquid 
               
               
                 33 
                 III 
                 CH 3   
                 iso-C 5 H 11   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 liquid 
               
               
                 34 
                 III 
                 CH 3   
                 OOCCH 2   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 35 
                 III 
                 CH 3   
                 OOCCH 2 CH 2   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 36 
                 III 
                 CH 3   
                 (NH 2 )OCCH 2   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 37 
                 III 
                 CH 3   
                 (NH 2 )OCCH 2 CH 2   
                 H 
                 Light yellow 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 38 
                 III 
                 CH 3   
                 C 3 H 7 CHCN 
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 39 
                 III 
                 CH 3   
                 iso-C 3 H 7   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 40 
                 III 
                 CH 3   
                 C 3 H 7 CHCl 
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 41 
                 III 
                 CH 3   
                 CH 3 SCH 2 CH 2   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 solid 
               
               
                 42 
                 III 
                 C 2 H 5   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 43 
                 III 
                 ClC 2 H4 
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 44 
                 III 
                 FC 2 H4 
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 45 
                 III 
                 C 2 H 5 OC 2 H 5   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 46 
                 III 
                 PhCH 2 CH 2 O 
                 S6C-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 47 
                 III 
                 PhOCH 2 CH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 48 
                 III 
                 (m-diCl)PhCH 2 CH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 49 
                 III 
                 PhCH 2 NH 
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 50 
                 III 
                 THF-CH 2 CH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 51 
                 III 
                 PhCH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 52 
                 III 
                 p-NO 2 PhCH 2   
                 sec-C 4 H 9   
                 H 
                 Light brown 
               
               
                   
                   
                   
                   
                   
                 viscous liquid 
               
               
                 53 
                 IV 
                 CH 3   
                 C 3 H 7 CHCN 
                 H 
                 Brown viscous 
               
               
                   
                   
                   
                   
                   
                 liquid 
               
               
                 54 
                 IV 
                 CH 3   
                 C 5 H 11 CHCN 
                 H 
                 Brown oil liquid 
               
               
                 55 
                 IV 
                 CH 3   
                 C 7 H 13 CHCN 
                 H 
                 Brown oil liquid 
               
               
                 56 
                 IV 
                 CH 3   
                 C 7 H 13 CHF 
                 H 
                 Brown oil liquid 
               
               
                 57 
                 V 
                 CH 3   
                 CH 3   
                 H 
                 Yellow needle 
               
               
                   
                   
                   
                   
                   
                 crystal 
               
               
                   
               
             
          
         
       
     
         [0068]    The study results showed different herbicidal activities of the above compounds. The different compounds also effect the Hill reaction rate and fluorescence of the chlorophyll. 
       Example 3 
       [0069]    3-Acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone analogue (Table 3, compounds 10-57) was dissolved in small amount of methanol. The solution was then diluted with distilled water to a concentration of 50 μg/mL. Methanol solution with same concentration and pure distilled water were used as control of the experiment. A pathogenic test was conducted by placing the toxic liquid on the slightly wounded leaf of Crofton weed with a needle. The experiment was carried out at 25° C. under the natural light and each test was repeated 6 times. It was measure the diameter of the spot after 24 h. The experimental results are listed in Table 4. The data indicated that most of the 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone analogs have high herbicidal activity. The size of the side chain also has an effect on their activity. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Comparison of the toxicity of 3-acetyl-4-hydroxy-5-sec- 
               
               
                 butylpyrroline-2-ketone analogs with formula (III), (IV), (V) 
               
             
          
           
               
                   
                 Time of Disease spot 
                 Average diameter of 
               
               
                 Treatment 
                 (h) 
                 spot after 24 h (mm) 
               
               
                   
               
               
                 H 2 O Control 
                 / 
                 0.23 ± 0.02 
               
               
                 Methanol 
                 / 
                 0.27 ± 0.14 
               
               
                 control 
               
               
                 10 
                   29 ± 6.30 
                 1.11 ± 0.16 
               
               
                 11 
                 21.5 ± 0   
                 1.80 ± 0.41 
               
               
                 12 
                 15.2 ± 0.35 
                 2.77 ± 0.23 
               
               
                 13 
                 16.70 ± 0.21  
                 5.21 ± 0.44 
               
               
                 14 
                 13.80 ± 0.54  
                 6.37 ± 0.04 
               
               
                 15 
                  9.5 ± 1.26 
                 9.61 ± 1.20 
               
               
                 16 
                 13.80 ± 0.54  
                 7.61 ± 0.11 
               
               
                 17 
                  9.5 ± 2.36 
                 7.94 ± 1.30 
               
               
                 18 
                 12.00 ± 0.48  
                 8.27 ± 0.61 
               
               
                 19 
                   24 ± 4.00 
                 1.24 ± 0.10 
               
               
                 20 
                 21.1 ± 3.56 
                 1.57 ± 0.04 
               
               
                 21 
                 16.5 ± 1.30 
                 2.89 ± 0.14 
               
               
                 22 
                 20.0 ± 1.63 
                 1.76 ± 0.24 
               
               
                 23 
                 18.3 ± 2.17 
                 2.23 ± 0.12 
               
               
                 24 
                 16.21 ± 3.55  
                 2.43 ± 0.07 
               
               
                 25 
                 15.22 ± 2.00  
                 2.44 ± 0.10 
               
               
                 26 
                 13.61 ± 1.35  
                 3.31 ± 0.07 
               
               
                 27 
                 14.2 ± 4.15 
                 3.18 ± 0.93 
               
               
                 28 
                 16.9 ± 2.25 
                 2.40 ± 0.11 
               
               
                 29 
                 12.1 ± 3.75 
                 5.77 ± 1.15 
               
               
                 30 
                 13.3 ± 2.00 
                 4.53 ± 1.03 
               
               
                 31 
                 10.8 ± 2.00 
                 5.93 ± 1.35 
               
               
                 32 
                 12.5 ± 3.75 
                 4.82 ± 1.44 
               
               
                 33 
                 13.5 ± 0.75 
                 4.17 ± 1.15 
               
               
                 34 
                 24.0 ± 0.02 
                   1 ± 0.86 
               
               
                 35 
                 26.4 ± 0.12 
                 1.27 ± 0.02 
               
               
                 36 
                 21.9 ± 0.23 
                 1.54 ± 0.07 
               
               
                 37 
                   24 ± 0.08 
                 1.64 ± 0.25 
               
               
                 38 
                 13.6 ± 0.50 
                 9.82 ± 0.02 
               
               
                 39 
                 16.5 ± 2.15 
                 4.89 ± 0.37 
               
               
                 40 
                 11.93 ± 0.66  
                 8.10 ± 0.90 
               
               
                 41 
                 20.8 ± 3.00 
                 2.45 ± 0.24 
               
               
                 42 
                 19.4 ± 2.50 
                 2.24 ± 0.45 
               
               
                 43 
                 20.1 ± 1.15 
                 2.30 ± 0.28 
               
               
                 44 
                 12.0 ± 1.33 
                 4.07 ± 0.51 
               
               
                 45 
                 20.3 ± 0.57 
                 2.73 ± 0.73 
               
               
                 46 
                 22.1 ± 1.35 
                 2.31 ± 0.44 
               
               
                 47 
                 21.2 ± 1.88 
                 2.12 ± 0.09 
               
               
                 48 
                 13.5 ± 2.77 
                 4.33 ± 0.54 
               
               
                 49 
                 23.2 ± 2.86 
                 2.47 ± 0.08 
               
               
                 50 
                 22.6 ± 0.69 
                 2.66 ± 0.46 
               
               
                 51 
                 15.1 ± 1.82 
                 3.28 ± 1.12 
               
               
                 52 
                 15.3 ± 1.72 
                 3.83 ± 1.03 
               
               
                 53 
                 12.90 ± 0.27  
                 7.334 ± 0.845 
               
               
                 54 
                 11.30 ± 0.73  
                 8.211 ± 0.101 
               
               
                 55 
                 9.81 ± 0.33 
                 8.931 ± 0.086 
               
               
                 56 
                 14.00 ± 1.09  
                 6.927 ± 0.317 
               
               
                 57 
                 20.4 ± 0   
                 1.98 ± 0.51 
               
               
                   
               
             
          
         
       
     
       Example 4 
       [0070]    Compounds 1, 2, 3 and 40 were separately dissolved in a small amount of methanol. The solutions were then diluted with distilled water to a concentration of 50 μg/mL. A mixture of methanol and water in the same ratio as the sample solution was also prepared and used as control in the experiment. The solutions were sprayed on leaves and stems of three-leaf-stage Crofton weed seedlings. All the plants were grown in pot in a greenhouse. The leaves were properly wet by the solutions for consistency and the treatment was repeated 3 times. The plant damage assessment was conducted two days later and the results were listed in Table 5. The measurement of the plant damage was calculated by the formula: Damage Index=Σ(damage level×number of plants)×100/4/number of plants in each treatment. The calculated results are listed in Table 6. 
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Standard of evaluation of weed damage 
               
             
          
           
               
                 Damage Level 
                 Description 
               
               
                   
               
               
                 4 
                 Plant completely dead 
               
               
                 3 
                 Two thirds of the plant stems and leaves dried out 
               
               
                 2 
                 Half of the plant stems and leaves dried out 
               
               
                 1 
                 One third of the plant stems and leaves dried out 
               
               
                 0 
                 No damage at all 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 6 
               
             
             
               
                   
               
               
                 Weed damage assessment results 
               
             
          
           
               
                   
                 Treatment 
                 Damage Level 
               
               
                   
                   
               
               
                   
                 H 2 O control 
                 0 
               
               
                   
                 Methanol control 
                 0 
               
               
                   
                 1 
                 2 
               
               
                   
                 2 
                 2 
               
               
                   
                 3 
                 1 
               
               
                   
                 40  
                 4 
               
               
                   
                   
               
             
          
         
       
     
         [0071]    The data in the Table 6 suggests that the analogs of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone have good herbicidal activity against Crofton weed. Substitution of chlorine on the side chain increases their activity. 
       Example 5 
       [0072]    Compound 10-57 were dissolved in small amount of methanol. The solutions were then diluted with distilled water to a concentration of 50 μg/mL. A mixture of methanol and water in the same ratio as the sample solution was also prepared and used as control in the experiment. The healthy leaves of Crofton weed were washed in water for 30 minutes and then rinsed with distilled water. The clean and tissue dried leaves were placed in petri dish with the back-side of the leaves facing up. Wet filter paper was also placed in the in petri dish for moisture control. Water, methanol and chemical solutions of the analogues were applied to the back-side of each leaf. Test sample was then placed in vacuum chamber at 25° C. for 15 min followed by exposure to the strong light (400 μM m −2  s −1 ) for 12 hours. The leaf sample went through a series of test, and the Hill reaction rate, the electron transfer activity and fluorescence of chlorophyll were measured. Four leaves were used for each treatment and each test was repeated three times. 
         [0073]    The experiment results indicate that compound 10 to 57 can slow the Hill reaction and inhibit the electron transfer of photosystem II, but has no effect in photosystem I. As the experimental data in Table 7 indicated that compounds having chlorinated side-chain have more inhibitory effect on the activity of Hill reaction and electron transfer in photosystem II than the compounds whose side chain are not substituted by halogen. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 7 
               
             
             
               
                   
               
               
                 Effects to the photosynthesis of Crofton weed 
               
             
          
           
               
                   
                   
                 PSII Activity of 
                   
                   
               
               
                   
                 Activity of Hill 
                 oxygen 
                   
                 The t 1/2  of 
               
               
                   
                 Reaction 
                 evolution of 
                   
                 fluorescence 
               
               
                 Treatment 
                 (μMO 2 /mgChlh) 
                 (μMO 2 /mgChlh) 
                 F v /F m   
                 rise (ms) 
               
               
                   
               
             
          
           
               
                 H 2 O control 
                 130.11 
                 65.34 
                 0.83 
                 1339 
               
               
                 Methanol 
                 124.38 
                 60.89 
                 0.81 
                 1382 
               
               
                 control 
               
               
                 1 
                 98.76 
                 50.89 
                 0.82 
                 1184 
               
               
                 2 
                 69.41 
                 37.02 
                 0.84 
                 1055 
               
               
                 3 
                 62.21 
                 32.14 
                 0.83 
                 1172 
               
               
                 4 
                 51.13 
                 28.01 
                 0.83 
                 791 
               
               
                 5 
                 52.31 
                 24.10 
                 0.82 
                 826 
               
               
                 6 
                 50.04 
                 27.11 
                 0.81 
                 773 
               
               
                 7 
                 52.41 
                 29.17 
                 0.82 
                 809 
               
               
                 8 
                 49.05 
                 24.65 
                 0.79 
                 725 
               
               
                 9 
                 50.12 
                 23.33 
                 0.83 
                 733 
               
               
                 10 
                 84.32 
                 47.55 
                 0.79 
                 1176 
               
               
                 11 
                 80.00 
                 46.41 
                 0.82 
                 1181 
               
               
                 12 
                 70.32 
                 34.54 
                 0.83 
                 925 
               
               
                 13 
                 78.19 
                 41.35 
                 0.85 
                 1000 
               
               
                 14 
                 67.37 
                 34.01 
                 0.79 
                 910 
               
               
                 15 
                 62.77 
                 31.26 
                 0.78 
                 946 
               
               
                 16 
                 61.43 
                 30.00 
                 0.83 
                 880 
               
               
                 17 
                 57.13 
                 27.04 
                 0.82 
                 917 
               
               
                 18 
                 67.27 
                 39.98 
                 0.80 
                 913 
               
               
                 19 
                 63.43 
                 40.07 
                 0.79 
                 962 
               
               
                 20 
                 57.23 
                 43.40 
                 0.82 
                 876 
               
               
                 21 
                 62.34 
                 42.25 
                 0.77 
                 879 
               
               
                 22 
                 56.16 
                 38.05 
                 0.82 
                 828 
               
               
                 23 
                 63.28 
                 38.24 
                 0.79 
                 855 
               
               
                 24 
                 71.37 
                 43.01 
                 0.83 
                 921 
               
               
                 25 
                 97.55 
                 57.12 
                 0.82 
                 1197 
               
               
                 26 
                 89.15 
                 58.01 
                 0.82 
                 1211 
               
               
                 27 
                 91.45 
                 53.24 
                 0.81 
                 1232 
               
               
                 28 
                 75.03 
                 31.76 
                 0.82 
                 1124 
               
               
                 30 
                 47.33 
                 22.78 
                 0.79 
                 747 
               
               
                 32 
                 63.42 
                 32.13 
                 0.82 
                 905 
               
               
                 33 
                 51.94 
                 26.54 
                 0.79 
                 791 
               
               
                 34 
                 65.73 
                 35.11 
                 0.81 
                 922 
               
               
                 38 
                 64.69 
                 40.41 
                 0.81 
                 871 
               
               
                 39 
                 62.72 
                 33.79 
                 0.80 
                 884 
               
               
                 40 
                 46.20 
                 24.00 
                 0.82 
                 720 
               
               
                 41 
                 59.07 
                 41.32 
                 0.83 
                 901 
               
               
                 43 
                 63.35 
                 47.80 
                 0.83 
                 880 
               
               
                 44 
                 59.15 
                 40.75 
                 0.79 
                 839 
               
               
                 45 
                 41.00 
                 27.04 
                 0.79 
                 713 
               
               
                 46 
                 58.78 
                 43.67 
                 0.82 
                 899 
               
               
                 47 
                 67.99 
                 49.01 
                 0.82 
                 844 
               
               
                 51 
                 52.23 
                 32.15 
                 0.81 
                 798 
               
               
                 52 
                 53.13 
                 36.86 
                 0.82 
                 814 
               
               
                 53 
                 42.72 
                 32.12 
                 0.79 
                 739 
               
               
                 54 
                 43.65 
                 31.98 
                 0.81 
                 741 
               
               
                 55 
                 42.72 
                 28.63 
                 0.79 
                 727 
               
               
                 56 
                 42.72 
                 29.02 
                 0.79 
                 719 
               
               
                 57 
                 63.42 
                 35.13 
                 0.82 
                 955 
               
               
                   
               
             
          
         
       
     
       Example 6 
       [0074]    Fourteen salts of 3-acetyl-4-hydroxy-5-sec-butylpyrroline-2-ketone analogs were dissolved in small amount of methanol and diluted with distilled water to a concentration of 50 μg/mL. Methanol/water mixture was also prepared and used as control. Needle puncture method was used for the test on the small pieces of Crofton weed. Each treatment was repeated six times or more. The test samples were kept under natural light at 25° C. for 24 hours. The diameters of damaged spot of the plant leaves were measured by vernier caliper. These fourteen compounds are: 
       (a) Sodium salt of 4-Hydroxy-3-acetyl-pyrroline-2-ketone 
       [0075]    
       
                 
         
             
             
         
       
     
       (b) Sodium salt of 4-Hydroxy-3-acetyl-5-methylpyrroline-2-ketone 
       [0076]    
       
                 
         
             
             
         
       
     
       (c) Sodium salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0077]    
       
                 
         
             
             
         
       
     
       (d) Sodium salt of 4-Hydroxy-3-acetyl-5-benzylpyrroline-2-ketone 
       [0078]    
       
                 
         
             
             
         
       
     
       (e) Sodium salt of 4-Hydroxy-3-acetyl-5-propenylpyrroline-2-ketone 
       [0079]    
       
                 
         
             
             
         
       
     
       (f) Potassium salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0080]    
       
                 
         
             
             
         
       
     
       (g) Calcium salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0081]    
       
                 
         
             
             
         
       
     
       (h) Magnesium (II) salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0082]    
       
                 
         
             
             
         
       
     
       (i) Manganese salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0083]    
       
                 
         
             
             
         
       
     
       (j) Zinc salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0084]    
       
                 
         
             
             
         
       
     
       (k) Iron salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0085]    
       
                 
         
             
             
         
       
     
       (l) Copper salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0086]    
       
                 
         
             
             
         
       
     
       (m) Sodium salt of 4-Hydroxy-3-acetyl-5-(iso-pentanyl)pyrroline-2-ketone 
       [0087]    
       
                 
         
             
             
         
       
     
       (n) Zinc salt of 4-Hydroxy-3-acetyl-5,5′-dimethylpyrroline-2-ketone 
       [0088]    
       
                 
         
             
             
         
       
     
       (o) Ammonium salt of 4-Hydroxy-3-acetyl-5-ethylpyrroline-2-ketone 
       [0089]    
       
                 
         
             
             
         
       
     
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 8 
               
             
             
               
                   
               
               
                 Herbicidal activity of 14 salts to Crofton weed 
               
             
          
           
               
                   
                   
                 Average diameter of 
               
               
                   
                   
                 the damage spot after 
               
               
                 Treatment 
                 time (h) 
                 24 h (mm) 
               
               
                   
               
               
                 H 2 O control 
                 / 
                 0.227 ± 0.002 
               
               
                 Methanol 
                 / 
                 0.273 ± 0.014 
               
               
                 control 
               
               
                 a 
                   26 ± 7.30 
                 1.34 ± 0.08 
               
               
                 b 
                 19.5 ± 0.5  
                 2.21 ± 0.18 
               
               
                 c 
                 14.5 ± 1.8  
                 3.11 ± 0.54 
               
               
                 d 
                 10.2 ± 2.50 
                 5.07 ± 0.11 
               
               
                 e 
                 16.8 ± 1.85 
                 2.42 ± 0.05 
               
               
                 f 
                 14.2 ± 2.00 
                 3.72 ± 0.28 
               
               
                 g 
                 18.7 ± 3.00 
                 2.29 ± 0.19 
               
               
                 h 
                 17.5 ± 1.50 
                 2.88 ± 0.10 
               
               
                 i 
                 14.3 ± 3.15 
                 3.24 ± 0.33 
               
               
                 j 
                 15.1 ± 4.00 
                 2.91 ± 0.02 
               
               
                 k 
                 17.2 ± 0.95 
                 1.72 ± 0.15 
               
               
                 l 
                 21.6 ± 3.05 
                 1.22 ± 0.25 
               
               
                 m 
                  8.5 ± 2.00 
                 8.27 ± 1.72 
               
               
                 n 
                 18.2 ± 2.50 
                 2.63 ± 0.06 
               
               
                 o 
                 10.3 ± 1.50 
                 4.97 ± 1.01 
               
               
                   
               
             
          
         
       
     
         [0090]    Compared with the no-salt form (data are listed in Table 2 and Table 4), the salt form of these compounds is much more herbicidal. In addition, the ammonium salt, the sodium salt, the potassium salt, the magnesium salt and the zinc salt have higher activity than the calcium, magnesium and copper salts. 
       Example 7 
       [0091]    Compounds 7, 14, 15, 16, 40, 45, 48 and 53 were dissolved individually in small amount of methanol, and diluted with distilled water to concentration of 50 μg/mL. Methanol water solution and pure water were used as control. A piece of 5 mm leaf was taken from the second leaf of weed sample and was treated with the solution three times. 5 pieces of the leaf were prepared for each treatment. The damage data were collected 4 days later. The measurement of damage level is described in the Table 9. 
         [0000]    
       
         
               
             
               
               
             
           
               
                 TABLE 9 
               
             
             
               
                   
               
               
                 Standard of evaluation of weed damage 
               
             
          
           
               
                 Damage level 
                 Description 
               
               
                   
               
               
                 4 
                 The leaf completely dead 
               
               
                 3 
                 Two third of the leaf withered 
               
               
                 2 
                 One half of the leaf withered 
               
               
                 1 
                 Only edge of the leaf withered 
               
               
                 0 
                 Not damage at all 
               
               
                   
               
             
          
         
       
     
         [0092]    The measurement of the plant damage was calculated by the formula: Damage Index=Σ(damage level×number of plants)×100/4/number of plants in each treatment. The calculated results are listed in Table 10. 
         [0000]    
       
         
               
             
               
               
               
               
               
               
               
               
               
               
               
               
             
           
               
                 TABLE 10 
               
             
             
               
                   
               
               
                 Weed damage assessment results 
               
             
          
           
               
                   
                   
                   
                 Meth- 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Family 
                 Plant species 
                 H 2 O 
                 anol 
                 7 
                 14 
                 15 
                 16 
                 40 
                 44 
                 48 
                 53 
               
               
                   
               
               
                 Gramineae 
                 Goosegrass 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 4 
                 3 
                 3 
                 4 
               
               
                   
                 Wild oats 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
               
               
                   
                 Equal 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 4 
               
               
                   
                 
                   alopecurus 
                 
               
               
                   
                 Japanese 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 4 
                 4 
                 3 
               
               
                   
                 
                   alopecurus 
                 
               
               
                   
                 Keng stiffgrass 
                 0 
                 0 
                 4 
                 3 
                 3 
                 4 
                 3 
                 3 
                 4 
                 4 
               
               
                   
                 Common 
                 0 
                 0 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 4 
                 4 
               
               
                   
                 polypogon 
               
               
                   
                 Green foxtail 
                 0 
                 0 
                 4 
                 3 
                 4 
                 3 
                 3 
                 4 
                 4 
                 3 
               
               
                   
                 ( Setaria viridis ) 
               
               
                   
                 Crabgrass 
                 0 
                 0 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
               
               
                   
                 ( Digitaria   
               
               
                   
                   sanguinalis ) 
               
               
                   
                 
                   Leptochloa 
                 
                 0 
                 0 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
               
               
                   
                 
                   chinensis 
                 
               
               
                   
                 Barbyardgrass 
                 0 
                 0 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
               
               
                   
                 
                   Echinochloa 
                 
               
               
                   
                 
                   crusgalli 
                 
               
               
                   
                 Big Bristlegass 
                 0 
                 0 
                 3 
                 2 
                 2 
                 3 
                 3 
                 2 
                 3 
                 3 
               
               
                 Amaranthaceae 
                 Redroot pigweed 
                 0 
                 0 
                 3 
                 2 
                 2 
                 3 
                 3 
                 2 
                 2 
                 3 
               
               
                   
                 ( Amaranthus   
               
               
                   
                   retroflexus ) 
               
               
                   
                 Alligator weed 
                 0 
                 0 
                 3 
                 3 
                 2 
                 3 
                 3 
                 4 
                 4 
                 3 
               
               
                   
                 ( Alternanthera   
               
               
                   
                   philoxeroides ) 
               
               
                   
                 Pigweed 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 2 
                 3 
                 3 
                 3 
               
               
                   
                 ( Amaranthus   
               
               
                   
                   spinosus ) 
               
               
                 Malvaceae 
                 
                   Malvaceae 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 3 
               
               
                   
                 
                   Abutilon 
                 
                 0 
                 0 
                 2 
                 2 
                 2 
                 3 
                 3 
                 2 
                 3 
                 3 
               
               
                   
                 
                   theophrasti 
                 
               
               
                 Polygonaceae 
                 
                   Polygonum 
                 
                 0 
                 0 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 3 
               
               
                   
                 
                   lapathifolium 
                 
               
               
                   
                 
                   Rumex 
                 
                 0 
                 0 
                 2 
                 1 
                 2 
                 2 
                 2 
                 3 
                 2 
                 3 
               
               
                   
                 
                   japonicus 
                 
               
               
                   
                 
                   Polygonum 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 3 
                 3 
                 3 
                 3 
                 3 
               
               
                   
                 
                   perfoliatum 
                 
               
               
                   
                 
                   Polygonum 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 3 
                 2 
                 3 
                 3 
                 3 
               
               
                   
                 
                   hydropiper 
                 
               
               
                   
                 
                   Rumex dentatus 
                 
                 0 
                 0 
                 2 
                 2 
                 2 
                 2 
                 2 
                 3 
                 3 
                 2 
               
               
                 Euphorbiaceae 
                 
                   Acalypha 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 3 
                 3 
                 3 
                 2 
               
               
                   
                 
                   australis 
                 
               
               
                 Cannabinaceae 
                 
                   Humulus 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 3 
                 3 
                 2 
                 3 
                 2 
               
               
                   
                 
                   scandens 
                 
               
               
                 Labiatae 
                 
                   Perilla 
                 
                 0 
                 0 
                 2 
                 2 
                 3 
                 2 
                 2 
                 3 
                 2 
                 2 
               
               
                   
                 
                   frutescens 
                 
               
               
                   
                 
                   Galeopsis bifida 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 3 
                 3 
                 2 
                 3 
               
               
                   
                 
                   Lamium 
                 
                 0 
                 0 
                 3 
                 2 
                 3 
                 2 
                 3 
                 3 
                 2 
                 2 
               
               
                   
                 
                   amplexicaule 
                 
               
               
                   
                 
                   Mosla scabra 
                 
                 0 
                 0 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                 Scrophulariaceae 
                 
                   Veronica 
                 
                 0 
                 0 
                 2 
                 3 
                 2 
                 2 
                 2 
                 3 
                 3 
                 3 
               
               
                   
                 
                   didyma 
                 
               
               
                   
                 
                   Veronica 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 3 
                 3 
                 3 
                 3 
               
               
                   
                 
                   persica 
                 
               
               
                 Commelinaceae 
                 
                   Commelina 
                 
                 0 
                 0 
                 4 
                 2 
                 2 
                 3 
                 3 
                 2 
                 4 
                 3 
               
               
                   
                 
                   communis 
                 
               
               
                   
                 
                   Commelina 
                 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 3 
               
               
                   
                 
                   bengalensis 
                 
               
               
                 Convolvulaceae 
                 Japanese false 
                 0 
                 0 
                 4 
                 3 
                 3 
                 4 
                 3 
                 4 
                 4 
                 4 
               
               
                   
                 bindweed 
               
               
                   
                 ( Calystegia   
               
               
                   
                   hederacea ) 
               
               
                   
                 
                   Dichondra 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 3 
                 3 
                 2 
                 3 
                 2 
               
               
                   
                 
                   repens 
                 
               
               
                   
                 
                   Pharbitis nil 
                 
                 0 
                 0 
                 2 
                 2 
                 3 
                 2 
                 2 
                 3 
                 3 
                 3 
               
               
                 Compositae 
                 
                   Lapsana 
                 
                 0 
                 0 
                 4 
                 3 
                 2 
                 3 
                 3 
                 3 
                 4 
                 3 
               
               
                   
                 
                   apogonoides 
                 
               
               
                   
                 
                   Xanthium 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 2 
                 2 
                 3 
                 3 
               
               
                   
                 
                   sibiricum 
                 
               
               
                   
                 
                   Conyza 
                 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 4 
                 4 
                 3 
               
               
                   
                 
                   canadensis 
                 
               
               
                   
                 
                   Eclipta prostrata 
                 
                 0 
                 0 
                 4 
                 3 
                 4 
                 3 
                 3 
                 4 
                 4 
                 4 
               
               
                   
                 
                   Sonchus 
                 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 4 
               
               
                   
                 
                   oleraceus 
                 
               
               
                   
                 
                   Aster 
                 
                 0 
                 0 
                 4 
                 3 
                 3 
                 4 
                 3 
                 4 
                 4 
                 4 
               
               
                   
                   ageratoides  var. 
               
               
                   
                 
                   scaberulus 
                 
               
               
                   
                 
                   Youngia 
                 
                 0 
                 0 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
               
               
                   
                 
                   japonica 
                 
               
               
                   
                 
                   Sonchus asper 
                 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 3 
               
               
                   
                 
                   Cirsium 
                 
                 0 
                 0 
                 3 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 4 
               
               
                   
                 
                   setosum 
                 
               
               
                   
                 
                   Erigeron annuus 
                 
                 0 
                 0 
                 3 
                 3 
                 4 
                 3 
                 3 
                 4 
                 4 
                 3 
               
               
                   
                 
                   Ambrosia 
                 
                 0 
                 0 
                 3 
                 3 
                 2 
                 3 
                 3 
                 4 
                 3 
                 3 
               
               
                   
                 
                   artemisiifolia 
                 
               
               
                   
                 
                   Carpesium 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 3 
                 3 
                 4 
                 2 
               
               
                   
                 
                   abrotanoides 
                 
               
               
                   
                 
                   Eupatorium 
                 
                 0 
                 0 
                 4 
                 3 
                 4 
                 4 
                 4 
                 4 
                 4 
                 4 
               
               
                   
                 
                   adenophorum 
                 
               
               
                   
                 
                   Trifolium 
                 
                 0 
                 0 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 4 
                 4 
               
               
                   
                 
                   pratense 
                 
               
               
                 Rosaceae 
                 
                   Duchesnea 
                 
                 0 
                 0 
                 2 
                 2 
                 3 
                 2 
                 2 
                 3 
                 3 
                 3 
               
               
                   
                 
                   indica 
                 
               
               
                 Vitaceae 
                 
                   Cayratia 
                 
                 0 
                 0 
                 2 
                 2 
                 2 
                 2 
                 2 
                 3 
                 3 
                 3 
               
               
                   
                 
                   japonica 
                 
               
               
                   
                 
                   Parthenocissus 
                 
                 0 
                 0 
                 2 
                 2 
                 3 
                 2 
                 2 
                 3 
                 3 
                 3 
               
               
                   
                 
                   tricuspidata 
                 
               
               
                 Chenopodiaceae 
                 
                   Chenopodium 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 2 
                 2 
                 3 
                 3 
                 3 
               
               
                   
                 
                   serotinum 
                 
               
               
                 Oxalidaceae 
                 
                   Oxalis 
                 
                 0 
                 0 
                 4 
                 4 
                 3 
                 4 
                 4 
                 4 
                 4 
                 4 
               
               
                   
                 
                   corniculata 
                 
               
               
                 Plantaginaceae 
                 
                   Plantago 
                 
                 0 
                 0 
                 3 
                 2 
                 3 
                 2 
                 3 
                 3 
                 2 
                 2 
               
               
                   
                 
                   asiatica 
                 
               
               
                 Cyperaceae 
                 
                   Cyperus 
                 
                 0 
                 0 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
                 2 
               
               
                   
                 
                   rotundus 
                 
               
               
                   
                 
                   Cyperus 
                 
                 0 
                 0 
                 4 
                 3 
                 3 
                 3 
                 3 
                 3 
                 4 
                 3 
               
               
                   
                 
                   difformis 
                 
               
               
                   
                 
                   Fimbristylis 
                 
                 0 
                 0 
                 3 
                 2 
                 2 
                 3 
                 3 
                 2 
                 3 
                 2 
               
               
                   
                 
                   miliacea 
                 
               
               
                   
               
             
          
         
       
     
         [0093]    The results listed in the table 10 suggest that eight compounds (7, 14, 15, 16, 40, 44, 48, and 53) have potential to be used to control or kill grassy weed such as Common crabgrass, Bbarnyardgrass, Difformed galingale, broadleaf weeds, Yerbadetajo, Copperleaf, Chenopodium serotinum, Commelina communis, Alligator weed, Redroot pigweed, Japanese false bindweed, Sonchus oleraceus etc. 
       Example 8 
       [0094]    Compound 1, 2, 3 and 40 were dissolved in small amount of methanol and diluted with distilled water to concentration of 50 μg/mL. The solution was sprayed to the soil sample until the soil was wet but not overflows. After standing at room temperature for 3 hours, the soil sample was washed with water and methanol. The wash solution was collected and concentrated. Such process was repeated three times. The concentrated solutions were used for herbicidal activity test using the method of needle puncture on Crofton weed. Methanol water solution and pure water were used as control. The experiment for every sample was repeated six times. The spot diameters were measured with vernier caliper after the plant was kept under natural light at 25° C. for 24 hours (Table 11). 
         [0000]    
       
         
               
             
               
               
               
             
               
               
               
             
               
               
             
               
               
               
             
           
               
                 TABLE 11 
               
             
             
               
                   
               
               
                 Evaluation compound toxicity after they were treated with soil 
               
             
          
           
               
                   
                 Average diameter of the spot after 24 h (mm) 
                   
               
             
          
           
               
                 Treatment 
                 H 2 O wash 
                 Methanol wash 
               
               
                   
               
             
          
           
               
                 H 2 O control 
                 0.234 ± 0.045 
               
               
                 Methanol 
                 0.288 ± 0.024 
               
               
                 control 
               
             
          
           
               
                 1 
                 0.223 ± 0.077 
                 0.292 ± 0.041 
               
               
                 2 
                 0.280 ± 0.030 
                 0.362 ± 0.012 
               
               
                 3 
                 0.273 ± 0.062 
                 0.334 ± 0.082 
               
               
                 40  
                 0.336 ± 0.050 
                 0.416 ± 0.024 
               
               
                   
               
             
          
         
       
     
         [0095]    Based on data listed in Table 11, it is clear that the herbicidal activity of all 4 compounds were completely lost after the soil treatment.