Sugar derivatives comprising oxiranes or α, β-unsaturated γ-lactones, process for their preparation and their utilisation as pesticides

A method for controlling pests, the method comprising applying an effective amount to pests or their locus of one or more compounds of general formula (I)wherein R1 and R2 represent, independently from each other, hydrogen, halogen, alkoxy, substituted alkoxy or an ester group; R1 and R2, together with the carbon atoms to which they are attached, represent an oxirane ring; R1 and R2, taken together, represent an akylidenedioxy or substituted alkylidenedioxy group; and R3 represents —CH2R6, wherein R6 represents an ester group, oxiranyl, or a group of formulawherein R7 represents hydrogen or alkyl, R8 represents phenylsulfanyl, phenylselenyl, phenylsulfoxy or phenylselenoxy, and R9 represents hydrogen, ethoxycarbonyl or carbamoyl; and R4 represents, independently, hydrogen, alkoxy or substituted alkoxy, or R1 and R4, taken together, represent an alkylidenedioxy or a substituted alkylidenedioxy group; wherein the pest dies as a result of contact with the compound.

FIELD OF THE INVENTION

The present invention relates to sugar derivatives comprising oxiranes or α,β-unsaturated γ-lactones with pesticidal, particularly insecticidal, activity, to processes for their preparation and their utilisation as pesticides, which are particularly effective against fruit fly, domestic fly and white fly.

BACKGROUND OF THE INVENTION

Compounds with the α,β-unsaturated γ-lactone moiety in their structure occur in the plant kingdom, as metabolites of lichens and fungi,1as sesquiterpene derivatives2or as steroid glycosides.3

Natural products possessing this structural element are also components of animal species such as sponges.4

Many of these compounds exhibit a variety of biologic activities such as antifungal, insecticidal, antibacterial, phytotoxic and anti-inflammatory. Some of them are antibiotics, potential anticancer agents and cyclooxygenase or phospholipase A2inhibitors.5

Due to their biological importance, several synthetic methods have been developed for the preparation of α,β-unsaturated γ-lactones. The synthesis of the endocyclic lactones (α,β-butenolides) is reported in the literature, and includes mercuration-carbonylation of propargylic alcohols,6condensation of 2,5-bis(trimethylsiloxy)furans with carbonyl compounds in the presence of titanium tetrachloride7and various transformations of C3synthons, such as, for example, glycidaldehyde.8

Other references report methods for the synthesis of γ-alkylidene-α,β-butenolides9and for the preparation of α,β-butenolide derivatives with insect antifeedant activity.10

A method for the preparation of the exocyclic type lactones involves the reaction of 2-(bromomethyl)acrylic acid in the presence of indium with carbonyl compounds, to give α-methylene-γ-butyrolactones in 7-96% yield.11

Previous work reports the synthesis of butenolides through the condensation of sugar epoxides with the dianion of phenylselenoacetic acid, followed by hydrolysis and subsequent oxidation of the intermediate phenylselenolactone.12,13,14The nucleophilic opening of the oxirane is stereospecific, the configuration of the stereogenic centre in the final lactone being determined by the centre of chirality of the starting epoxide.

Another method for the synthesis of α,β-unsaturated γ-lactones involves a Reformatsky type reaction of a ketosugar or a dialdofuranose with ethyl bromomethylacrylate and zinc in THF under reflux.13,14,15

Ethyl bromomethylacrylate and zinc-silver/graphite at −78° C have been successfully applied to the synthesis of hydroxyesters from cyclic ketones,16ketosugars and a 2,3-O-isopropylidene-D-erythronolactone17and to the synthesis of α,β-unsaturated γ-lactones from some ketosugars.16

The synthesis of 3-ulosonic acids via a samarium iodide Reformatsky reaction of aldonolactones was also reported.18

Some of this type of compounds, reported in the literature, have fungicidal efficacy.13

Epoxy sugars are versatile intermediates in organic synthesis, due to the ease of their preparation from a variety of starting materials and due to their susceptibility to reactions for example with electrophiles, nucleophiles, acids and bases. Furthermore, epoxides are part of a range of compounds recognised as active principles, with biological and pharmacological activity.19Reference can be made for example to cytotoxic metabolites, namely crotepoxide, pipoxide and senepoxide, the latter playing an important role in plants as an antiparasitic agent.20

Methods for the preparation of epoxysugars use halohydrins as intermediate compounds,21and also aminosugars,22tosylates and/or mesylates,23vicinal diols,24,25glycals26and carbonyl compounds.27

SUMMARY OF THE INVENTION

This invention is related to methods of pesticidal use of compounds of general formula (I) described further on.

These compounds possess efficacy as insecticides with high toxicity to fruit fly (Drosophila melanogaster), house fly (Musca domestica) and white fly (Trialeurodes vaporarium).

On the other hand the compounds are not toxic to brine shrimps (Artemia salina), the reference organisms in assays to evaluate the potential toxicity hazard to organisms in ecosystems.

DETAILED DESCRIPTION OF THE INVENTION

The invention is directed to the use, as pesticides, of a family of compounds of general formula (I):

whereinrepresents a carbon-carbon single or double bond;represents —CH(R4)—, if said carbon-carbon bond is a single bond,whereinR4represents, independently, hydrogen, alkoxy or substituted alkoxy, orR1and R4, taken together, represent an alkylidenedioxy or substituted alkylidenedioxy group; orrepresents ═C(R5)—C(═O)—, if said carbon-carbon bond is a double bond,wherein:R5represents hydrogen or halogen;R1and R2represent, independently, hydrogen, halogen, alkoxy, substituted alkoxy or an ester group; orR1and R2, together with the carbon atoms to which they are attached, represent an oxirane ring; orR1and R2, taken together, represent an akylidenedioxy or substituted alkylidenedioxy group; andR3represents —CH2R6,whereinR6represents an ester group, oxiranyl, or a group of formula

In a first embodiment, the invention is directed to methods for use as pesticides, of a subgroup of compounds of the formula (I′):

whereinR1and R2represent, independently from each other, hydrogen, halogen, alkoxy, substituted alkoxy or an ester group; orR1and R2, together with the carbon atoms to which they are attached, represent an oxirane ring; orR1and R2, taken together, represent an akylidenedioxy or substituted alkylidenedioxy group; andR3represents —CH2R6,whereinR6represents an ester group, oxiranyl, or a group of formula

In various embodiments, the compounds disclosed herein are used as arthropodicides.

In various further embodiments, the compounds disclosed herein are used as insecticides.

In various further embodiments, the compounds disclosed herein are used with special efficacy as insecticides with high toxicity in the control of fruit fly (Drosophila melanogaster), housefly (Musca domestica) and whitefly (Trialeurodes vaporarium).

In a third embodiment, the invention relates to the use, as pesticides, of a subgroup of compounds within the family of compounds of formula (I) or (I′), whereinR1and R2represent, independently from each other, hydrogen, alkoxy, substituted alkoxy or an ester group; orR1and R2, together with the carbon atoms to which they are attached, represent an oxirane ring; orR1and R2, taken together, represent an akylidenedioxy or substituted alkylidenedioxy group; andR3represents a group of formula

In a fourth embodiment, the invention relates to a subgroup of compounds within the family of compounds of formula (I), whereinrepresents a carbon-carbon single bond;represents —CH(R4)—,whereinR4represents, independently, hydrogen, alkoxy or substituted alkoxy, orR1and R4, taken together, represent an alkylidenedioxy or a substituted alkylidenedioxy group;R1and R2represent, independently, hydrogen, alkoxy, substituted alkoxy or an ester group, orR1and R2, together with the carbon atoms to which they are attached, represent an oxirane ring; orR1and R2, taken together, represent an alkylidenedioxy or substituted alkylidenedioxy group; andR3represents a group of formula

Preferred within this subgroup are the compounds of general formula (IA):

Especially preferred are the compounds of formula (IA), wherein R1and R4, taken together, represent the isopropylidenedioxy group, R2represents benzyloxy, R7represents methyl and R9represents hydrogen.

In a fifth embodiment, the invention relates to a subgroup of compounds within the family of compounds of formula (I), whereinrepresents a carbon-carbon double bond;represents ═C(R5)—C(═O)—,wherein,R5represents hydrogen or halogen;R1represents hydrogen or halogen; andR3represents —CH2R6,whereinR6represents an ester group.

Preferred within this subgroup are the compounds of general formula (IB):

wherein R1, R2, R5and R6have the meanings indicated for this fifth embodiment.

Especially preferred are the compounds of formula (IB), wherein R1represents hydrogen, R2represents —OC(═O)CH3, R5represents Br and R6represents —OC(═O)CH3.

Among these, the most especially preferred is the D-erythro derivative, i.e. 4,6-di-O-acetyl-2-bromo-2,3-dideoxy-D-erythro-hex-2-ene-1,5-lactone.

In a sixth embodiment, the invention relates to a subgroup of compounds within the family of compounds of formula (I), whereinrepresents a carbon-carbon single bond;represents —CH(R4)—,whereinR4represents, independently, hydrogen, alkoxy or substituted alkoxy, orR1and R4, taken together, represent an alkylidenedioxy or substituted alkylidenedioxy group;R1and R2represent, independently, hydrogen, alkoxy or substituted alkoxy, orR1and R2, together with the carbon atoms to which they are attached, represent an oxirane ring; orR1and R2, taken together, represent an alkylidenedioxy or a substituted alkylidenedioxy group; andR3represents a group of formula

Preferred within this subgroup are the compounds of general formula (IC):

Especially preferred are the compounds of formula (IC), wherein R1and R2, together with the carbon atoms to which they are attached, form an oxirane ring, R4represents methoxy, R7represents methyl, R8represents phenylselenyl and R9represents hydrogen.

Among these, the most especially preferred is the 2,3-anhydro-β-L-gulo derivative, i.e. methyl (7R)- and methyl (7S)-2,3-anhydro-6,7-dideoxy-7-methyl-7-phenylselenyl-β-L-gulo-octofuranurono-8,5-lactone.

Among these, the most especially preferred is theD-ribo derivative, i.e. (7R)- and (7S)-3,6,7-trideoxy-1,2-O-isopropylidene-7-methyl-7-phenylselenyl-α-D-ribo-octofuranuro-8,5-lactone.

Among these, the most especially preferred is theD-gluco derivative, i.e. (7R)- and (7S)-3-O-benzyl-6,7-dideoxy-1,2-O-isopropylidene-7-methyl-7-phenylselenyl-α-D-gluco-octofuranurono-8,5-lactone.

In a seventh embodiment, the invention relates to a subgroup of compounds, within the family of compounds of formula (I), whereinrepresents a carbon-carbon single bond;represents —CH(R4)—,whereinR4represents alkoxy or substituted alkoxy;R1and R2, taken together with the carbon atoms to which they are attached, represent an oxirane ring; andR3represents oxiranyl.

Preferred within this group are the compounds of general formula (ID):

wherein R4has the meaning indicated for this seventh embodiment.

Especially preferred are compounds of formula (ID), wherein R4represents methoxy.

Among these, the most preferred is the 2,3;5,6-dianhydro-β-L-gulo derivative, i.e. methyl 2,3;5,6-dianhydro-β-L-gulofuranoside.

In a eighth embodiment, the invention relates to a subgroup of compounds, within the family of compounds of formula (I), whereinrepresents a carbon-carbon single bond;represents —CH(R4)—,whereinR4represents, independently, hydrogen, alkoxy or substituted alkoxy, orR1and R4, taken together, represent an alkylidenedioxy or substituted alkylidenedioxy group; orR1and R2represent, independently, hydrogen, alkoxy or substituted alkoxy, orR1and R2, taken together, represent an alkylidenedioxy or substituted alkylidenedioxy group; andR3represents oxiranyl.

Preferred within this subgroup are compounds of general formula (IE):

wherein R1, R2and R4have the meanings indicated for the eighth embodiment.

A second object of the present invention is a process for the preparation of compounds of formula (I).

Synthesis of Compounds of Formula (IA)

Compounds of formula (IA) can be prepared by oxidation of phenylsulfanyllactones with m-chloroperbenzoic acid or with sodium metaperiodate, leading to the formation of sulfoxides which, upon pyrolysis in toluene at reflux, provide the corresponding butenolides. The transformation of the phenylselenyllactones into butenolides results from the oxidation with hydrogen peroxide, under acid catalysis. This synthesis is summarized in the following Scheme 1.

In Scheme 1, a lactone of formula (IC′) [compound of formula (IC), wherein R1and R4represent, taken together, isopropylidenedioxy, R2represents benzyloxy, R7represents hydrogen or methyl, R8represents XPh, wherein X represents S or Se, and R9represents hydrogen] is converted into a butenolide of formula (IA′) [compound of formula (IA), wherein R1and R4represent, taken together, isopropylidenedioxy, R2represents benzyloxy, R7represents hydrogen or methyl and R9represents hydrogen]. This conversion is carried out in the presence of m-chloroperbenzoic acid (when X represents S) and toluene at reflux, or in the presence of hydrogen peroxide, in acid medium (when X represents Se), at temperatures between −20° C. and room temperature.

Synthesis of Compounds of Formula (IB)

Compounds of formula (IB) can be prepared according to Scheme 2.

In Scheme 2, a compound of formula (II) is reacted with N-bromosuccinimide in the presence of tetrahydrofuran and water, at a temperature of 10° C. to 50° C., for a period of time from 4 to 24 hours. In a second step the product obtained is added to molecular sieves and pyridinium chlorochromate in dichloromethane, at a temperature of 10° C. to 50° C., for a period of time from 8 to 24 hours, to yield an α,β-unsaturated hexono-1,5-lactone of formula (IB′) [compound of formula (IB), wherein R1represents hydrogen, R2and R6represent acetoxy and R5represents bromo].

Synthesis of Compounds of Formula (IC)

Compounds of formula (IC) can be prepared by reaction of the corresponding epoxide precursor with dianions, namely: dianion of phenylselenoacetic acid, phenylselenopropionic acid and phenylthioacetic acid, which upon cyclization in acid medium yield the corresponding phenylselenyllactones or phenylsulfanyllactones, according to Schemes 3a and 3b.

In Scheme 3a, a diepoxide of formula (ID′) [compound of formula (ID), wherein R1and R2represent, taken together, oxiranyl and R4represents methoxy] is converted into a lactone of formula (IC″) [compound of formula (IC), wherein R1and R2represent, taken together, oxiranyl, R4represents methoxy, R7represents hydrogen or methyl, R8represents XPh, wherein X represents S or Se, and R9represents hydrogen]. This conversion is carried out by treatment of (ID′) with lithium diisopropropylamide in tetrahydrofuran, at a temperature between −10° C. and 10° C., followed by reaction with a compound of formula PhXCHR7CO2H (wherein X represents S or Se e R7represents hydrogen or methyl).

In Scheme 3b, following a procedure similar to that of Scheme 3a, an epoxide of formula (IE′) [compound of formula (IE), wherein R1and R4represent, taken together, isopropylidenedioxy and R2represents benzyloxy or hydrogen] is converted into a lactone of formula (IC′″) [compound of formula (IC), wherein R1and R4represent, taken together, isopropylidenedioxy, R2represents benzyloxy or hydrogen, R7represents hydrogen or methyl, R8represents XPh, wherein X represents S or Se, and R9represents hydrogen].

Synthesis of Compounds of Formula (ID)

Compounds of formula (ID) can be prepared according to Scheme 4.

In Scheme 4, a compound of formula (III) is converted into a diepoxide of formula (ID″) [compound of formula (ID), wherein R4represents methoxy]. This conversion is carried out by treatment of a compound of formula (III) with aqueous solution of potassium hydroxide and tetrahydrofuran, at a temperature between 5° C. and 40° C.

Synthesis of Compounds of Formula (IE)

Compounds of formula (IE) can be prepared according to Scheme 5.

In Scheme 5, a compound of formula (IV) is converted into an epoxide of formula (IE″) [compound of formula (IE), wherein R1and R4represent, taken together, isopropylidenedioxy and R2represents benzyloxy]. This conversion is carried out by conversion of compound of formula (IV) with triphenylphosphane in benzene, followed by the addition of molecular sieves and diethyl azodicarboxylate, at a temperature between 60° C. and 100° C., for a period of time of 1 to 4 days.

A third object of the instant invention is the use of compounds of any of the above formulas as pesticides.

Preferably, these compounds are used as arthropodicides.

More preferably, these compounds are used as insecticides.

Still more preferably, these compounds are used with particular efficacy as insecticides of high toxicity for controlling fruit fly (Drosophila melanogaster), house fly (Musca domestica) and white fly (Trialeurodes vaporarium).

A fourth object of the invention is a method for controlling pests, namely arthropods, particularly insects, especially fruit fly, house fly and white fly. Said method comprises the application of an effective amount of compounds of formula (I) to said pests or their locus.

EXPERIMENTAL

PREPARATION EXAMPLES

Preparation of 3-O-benzyl-6,7-dideoxy-1,2-O-isopropylidene-7-methyl-α-D-gluco-oct-6-enefuranurono-8,5-lactone (1)

Preparation of 3-O-benzyl-6,7-dideoxy-1,2-O-isopropylidene-7-methyl-α-D-alo-oct-6-enefuranurono-8,5-lactone (2)

Preparation of 3-O-benzyl-6,7-dideoxy-1,2-O-isopropylidene-α-D-alo-oct-6-enefuranurono-8,5-lactone (3)

Preparation of 3-O-benzyl-6,7-dideoxy-1,2-O-isopropylidene-α-D-gluco-oct-6-enefuranurono-8,5-lactone (4)

Preparation of compound 4,6-di-O-acetyl-2-bromo-2,3-dideoxy-D-erythro-hex-2-enone-1,5-lactone (5)

Preparation of methyl (7R)-/(7S)-2,3-anhydro-6,7-dideoxy-7-methyl-7-phenylselenyl-β-L-gulo-octofuranurono-8,5-lactone (6A/6B)

Preparation of (7R)-/(7S)-3,6,7-Trideoxy-1,2-O-isopropylidene-7-methyl-7-phenylselenyl-α-D-ribo-octofuranurono-8,5-lactone (7A/7B)

Preparation of (7R)-/(7S)-3-O-Benzyl-6,7-dideoxy-1,2-O-isopropylidene-7-methyl-7-phenylselenyl-α-D-gluco-octofuranurono-8,5-lactone (8A/8B)

a) Preparation of methyl 2,5-di-O-tosyl-β-D-glucofuranoside

Preparation of 5,6-anhydro-3-O-benzyl-1,2-O-isopropylidene-α-D-alofuranose

Biological Activity of the Compounds

Materials and Methods for Determination of Biological Activity

A range of arthropod species was chosen to represent those in the terrestrial, aerial and aquatic environment, covering important target pest groups such as house and fruit flies and the white fly, which belongs to a group of agricultural and horticultural pests.

Method A

Topical Treatment of Adult Fruit Fly (D. melanogaster)

A culture of fruit flies (D. melanogaster) was used in the production of adult flies (approx 0.22 mg) of about seven days.

Serial dilutions of the compounds were prepared in acetone, and volumes of approximately 0.2 μL were applied to the ventral surface of each insect, using a calibrated PAX 100 microapplicator and a 1 mL syringe.

The fruit flies, in groups of 5, were anaesthetised using carbon dioxide. Prior to recovery the flies were placed in a containing vial and kept at 30±1° C., for observations of mortality at 1, 2, 3 and 24 hours after treatment.

For this purpose solutions of 6 different concentrations and a control were employed in groups of 12 and 20 insects. Control mortalities were normally zero but occasionally rose to 5-10%.

Method B

Second Method for Topical Treatment of Adult Fruit Flies

Different dilutions of the compounds in acetone were prepared and applied to individual fruit flies using a Gilson piston micropipette.

Individual flies were held in padded forceps and 1 μL of acetone solution was applied. The acetone was allowed to evaporate before placing the fly into the vial for observation, kept at 30±1° C., following the standard methodology.

Method C

Method by Feeding Adult Fruit Fly (D. melanogaster)

Large glass vials were used which were fitted with caps, inside of which is inserted a piece of cotton wool. This was soaked in a 10% sugar solution containing the test compounds in a given concentration.

Care was taken to ensure that no solution dripped from the cotton wool and condensation was avoided by keeping the vials at room temperature (25° C.).

The fruit flies were anaesthetised using carbon dioxide and placed in the vials for recovery and feeding.

Method D

Topical Treatment of Fruit Fly Larvae

Fruit fly larvae were separated from the growing medium and second and third instars were topically treated with 0.2 μL acetone solutions of the compounds using a PAX microapplicator.

Larvae were held in padded forceps for dosing and then placed on moistened filter paper, at 30±1° C., for observation.

Method E

Topical Treatment of House Fly Adults (M. domestica)

A culture of an insecticide-susceptible strain, Cooper, was established. Three-day-old adult house flies (body weight about 1.8 mg) were anaesthetised with carbon dioxide. Using the PAX microapplicator, a volume of 1 μL of acetone solution of the test compounds was applied to the dorsal cuticle, holding the fly in padded forceps.

Groups of flies were placed into closed vials, kept at 30±1° C., for observation.

Method F

Immersion Bioassay of Brine ShrimpA. salinaLarvae in Brine

Freshly hatched brine shrimps were prepared by adding aquarium brine shrimp eggs to salt water (15 g sea salt per liter water). The following day hatchlings were separated from eggs and empty egg cases, using their phototropic movement and a Pasteur pipette.

Into each of a set of small glass vials was pipetted 195 μL of brine containing 5 shrimp larvae, using a micropipette. The solution of the test compound in 5 μL acetone was added, the vial closed and kept at 30±1° C. for observation.

Dead and alive shrimps were counted, at 1 and 24 hours after treatment, using a microscope. Six concentrations and a control were used with 10 shrimps treated.

A blank test was performed for comparison of the results.

Method G

Foliar Treatment of Glasshouse White Fly (T. vaporariorum)

Seedlings of tomato plants were infested with adult white fly. Selected leaves of the tomato plants were excised and carefully trimmed to 3 leaflets without disturbing the infestation. These were placed in glass tubes containing water and the leaflets were then sprayed on both sides with a small sprayer delivering for each one 200 μL of a solution of the test compound dissolved in 30% acetone in water.

Controls were sprayed with the solvent alone.

Counts of insects on the individual leaflets were made immediately after spraying and then at 14 hours following.

Calculation of Toxicity Parameters

Dosages used in insect treatments were based upon the amount of compound applied to each insect. For the shrimps the final concentrations of the compounds in the immersion brine were used.

The 24 hour mortalities were used to calculate the LD50/LC50using regression analysis of the probability percent mortality (probit) against log dose/concentration.30This was calculated using PoloPC software (LeOra Software, Berkeley, Calif., 1994).

Where single dose treatments were used (in the case of whitefly assays), no statistics are available and the results are expressed as percent effect.

Results

Toxicity to Fruit Fly (D. Melanogaster)

The results of assays with fruit flyD. Melanogasterare given in Table 1.

In the table are also given the confidence intervals at 95% for the LD50values, the number of organisms tested, the slope obtained by linear regression and the index g (of significance). Data are considered satisfactory if g is substancially less than 1 and seldom greater than 0.4.31

As regards the confidence intervals for LD50, the indication (90%) means that the intervals were calculated at 90% and not at 95%.

From the analysis of the LD50values, calculated through method 1, it is found that in general the compounds tested are active against adult fruit flies, compounds of Examples 1, 2, 3 and 9 being extremely active.

All of them are more active than imidacloprid, the reference insecticide for fruit fly.

The fruit fly larvae are less sensitive to the toxins than adult flies.

The values of LD50obtained for the compounds of Examples 5 and 8 are much higher than those obtained for the adult fly, therefore these compounds are less toxic for larvae than for adult flies.

Toxicity to House FlyM. domestica

Toxicity parameters for adult house flies, treated topically with compounds of Examples 5 and 8, are given in Table 2.

Although these insects are approximately 8 fold larger than fruit flies, analysis of said table allows to conclude that the compounds tested are much less toxic (2 to 3 orders of magnitude) for this type of flies than for fruit flies.

LD50values correspond only to a moderate insecticidal activity.

Toxicity to Brine Shrimp

Toxicity parameters for assays in which brine shrimp larvae are exposed to the compounds in saline solution are given in Table 3. Data obtained show good correlation (g<0.4) and high LC50values, indicating a low toxicity for this type of organisms.

Insecticidal Effect on Adult White Fly

The results of the bioassays of the insecticidal compounds on adult whitefliesT. vaporariorumare given in Table 4. Five compounds were tested, which were applied spraying 600 μL of each compound solution (prepared according to method G) on the leaves of tomato plants infested with a known number of adult whitefly. After 14 hours, the number of dead insects (or eventually of insects that disappeared) was counted. These assays were performed at room temperature, between 20 and 25° C.

From the data in Table 4, it is found that the compounds of Examples 4 and 9show effiacy as insecticides.

TABLE 4Insecticidal effect againts adult white fly, assayed by sprayinginfested tomato leaves.Compound No.Concentration (μg/mL)% Control of White Fly31.3042.55061.3074.8092.585

DISCUSSION AND CONCLUSIONS

Bioassays were performed using a range of compounds and treatment techniques in different species of arthropods. Adult fruit flies, treated topically, showed high levels of sensitivity to the compounds tested, such that the LD50values determined are much lower than that for the reference insecticide “imidacloprid”. However some variation was observed in the toxicity effect produced by the different compounds.

The slope of the log-probit regression line was generally small and much smaller than that for imidacloprid. When treated by incorporation into the adult diet the compounds were much less toxic. Topical treatment of the larval stage was also much less toxic but the regression line slope increased uniformly.

Some of the compounds were tested by topical application on adult house fly and were much less toxic compared to the fruit fly adults.

The slopes of the log-probit regression line were similar to those obtained by the same type of treatment used in adult fruit fly, suggesting a mechanism of action similar although with less activity and some selectivity.

Contrary to the high insectividal activity found, the compounds have a very low toxicity against brine shrimps.

The high values of LC50are associated with steep regression lines.

It can be concluded that these compounds show a very low toxicity towards this type of organisms in saline medium, not producing toxicity in these ecosystems.

In the test of spraying the compounds on leaves infested with adult white flies the compounds of Examples 4 and 9 were found to be promising for activity against the white fly. These compounds also showed high toxicity against adult fruit flies.

REFERENCES