Patent Publication Number: US-5633219-A

Title: 5H-pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino(2,3-C)(1,2,5)thiadiazole-5,7(6H)-dione, compositions containing them and their use as antimicrobial and marine antifouling agents

Description:
FIELD OF THE INVENTION 
     The present invention is directed to certain 5H-pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino(2,3-C)-(1,2,5)thiadiazole-5,7(6H)-dione, compositions containing these type of compounds and their use as antimicrobial and marine antifouling agents. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to the antimicrobial and marine antifouling uses of 5H-pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino(2,3-C)-(1,2,5)thiadiazole-5,7(6H)-dione corresponding to the formula ##STR2## wherein R represents --H, benzyl, phenethyl, a C 1  -C 10  straight or branched chain alkyl radical, a C 3  -C 10  cycloalkyl radical, a C 1  -C 10  straight or branched chain alkoxy radical, a C 3  -C 10  -cycloalkoxy, an ester of the formula --CH 2  CH 2  O--C(O)--R 1 , wherein R 1  represents a C 1  -C 6  straight or branched chain alkyl radical or a C 3  -C 6  cycloalkyl radical or R represents phenyl substituted with from 0-5 halo, C 1  -C 6  straight or branched chain alkyl, cyano, nitro groups, or an ester of the formula --OC(O)--R 1 , wherein R 1  represents a C 1  -C 6  straight or branched chain alkyl radical or a C 3  -C 6  cycloalkyl radical or an amide of the formula --C(O)--N(R 2 ) x , wherein each R 2  independently represents a C 1  -C 6  straight or branched chain alkyl radical or a C 3  -C 6  cycloalkyl radical. 
     The present invention is further directed to a method for inhibiting microorganisms present in a microbial habitat which comprises contacting said microbial habitat with an antimicrobial composition comprising an inert diluent in admixture with an antimicrobially-effective amount of a compound corresponding to Formula I. 
     The antimicrobial compositions of the present invention can also be employed to treat surfaces exposed to a marine environment in which marine organisms grow to prevent the growth of said marine organisms on said surfaces. 
     The dione compounds corresponding to Formula I of the present invention can be prepared employing a preparative procedure such as set forth below. In the following process schematic formulas, certain specific alkali metals, halo groups and specific solvents are set forth. These representations are only presented for convenience and are not to be considered as an indication that these specific representations are the only groups or materials which can be employed. 
     Preparation procedure: In the first step of this procedure, 3,4-dichloro-1,2,5-thiadiazole is reacted, with agitation and in a polar aprotic solvent, with an alkali metal sulfide to prepare the corresponding dialkali metal salt. 
     Representative polar solvents which can be employed in the present process include water, acetone, dimethylformamide, dimethylsulfoxide, dimethylacetamide and N-methylpyrrolidone. 
     The reactions are typically carried out at room temperature under a nitrogen atmosphere. The reactants may be added to the reaction mixture in any order of addition; conventionally they are added as a solution in the solvent used for the reaction. The reaction is allowed to continue over a period of from about ten minutes to about 15 hours. The reaction consumes the reactants in the ratio of one mole equivalent of the halide reactant per mole of the alkali metal sulfide reactant. To insure the completion of the reaction, an excess of the alkali metal sulfide reactant is normally employed. 
     After the completion of the reaction, a stoichiometric amount of an appropriately substituted dihalomaleimide is added to the reaction mixture (Step B) and the mixture is stirred at room temperature under a nitrogen atmosphere for a period of from about 3 to about 16 hours or more. In most cases the product precipitates out from the reaction mixture, if not, methanol and/or water can be added to aid in precipitation. The product is recovered by filtration, washed with water and/or methanol and air dried. The reaction scheme is as follows: ##STR3## 
     In the present specification and claims, the term &#34;alkali metal&#34; is employed to designate sodium, potassium, lithium or cesium. 
     In the present specification and claims, the term &#34;halo&#34; is employed to designate bromo, chloro, fluoro or iodo. 
     Since the hereinabove and hereinafter set forth compound preparation procedures employ only standard chemistry practices and it is known that slightly different reactants can require slightly different reaction parameters from those for other reactants, it is to be understood that minor modifications to the reaction parameters set forth such as the use of an excess of one reactant, the use of a catalyst, the use of temperatures slightly higher than room temperature and/or high speed mixing and other such conventional changes are within the scope of the present invention. 
     The structure identity of all compounds is confirmed by proton nuclear magnetic resonance spectroscopy ( 1  H NMR), recorded at 300 MHz; carbon nuclear magnetic resonance spectroscopy ( 13  C NMR) recorded at 75 MHz; infrared spectroscopy (IR) and mass spectrometry (MS). All of the reactions are conducted under a positive pressure of nitrogen. 
    
    
     The following examples illustrate the present invention and the manner by which it can be practiced but, as such, should not be construed as limitations upon the overall scope of the same. 
     EXAMPLE I 
     5H-Pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino-(2,3-C) (1,2,5)thiadiazole-5,7 (6H) -dione ##STR4## 
     A reaction mixture was prepared by slowly adding (3.7 grams (g), 0.024 mol) of 3,4-dichloro-1,2,5-thiadiazole to a solution of 11.6 g (0.048 mol) of sodium sulfide monohydrate (Na 2  S 9.sup.. H 2  O) in 50 mL of water. The mixture was stirred for 2 hours at room temperature. To this mixture was added 4.38 g (0.026 mol) of 3,4-dichloromaleimide and this mixture was stirred for 4 hours. The reaction mixture was poured into water and filtered. The title compound was recovered in a yield of 3 g (52 percent of theoretical) as a red solid melting at 232°-234° C.  13  C NMR (CDCl 3 ) δ 129.62, 146.03, 165.31; MS (EI) m/e 243 (M + ), 200, 172, 88. 
     EXAMPLE II 
     6-Methyl-5H-Pyrrolo (3&#39;,4&#39;:5,6)(1,4)dithiino-(2,3-C)(1,2,5)thiadiazole-5,7(6H) -dione ##STR5## 
     Following the procedure outlined in Example I, the title compound was prepared as an orange-red solid melting at 172°-173° C. in a yield of 4.44 g (54 percent of theoretical) by the reaction of 3.7 g (0.024 mol) of 3,4-dichloro-1,2,5-thiadiazole with 11.6 g (0.048 mol) of sodium sulfide followed by the addition of 4.38 g (0.026 mol) of 3,4-dichloro-N-methylmaleimide and the reaction thereof.  1  H NMR (CDCl 3 ) δ 3.06 (s, 3H);  13  C NMR (CDCl 3 ) δ 24.95, 130.05, 146.49, 164.26; MS (EI) m/e 257 (M + ), 200, 172, 88. 
     EXAMPLE III 
     6-Ethyl-5H-Pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino-(2,3-C)(1,2,5)thiadiazole-5,7(6H) -dione ##STR6## 
     Following the procedure outlined in Example I, the title compound was prepared as an orange-red solid melting at 114°-116° C. in a yield of 5.3 g (62 percent of theoretical) by the reaction of 5.0 g (0.032 mol) of 3,4-dichloro-1,2,5-thiadiazole with 17.0 g (0.07 mol) of sodium sulfide followed by the addition of 6.26 g (0.032 mol) of 3,4-dichloro-N-ethylmaleimide and the reaction thereof.  1  H NMR (CDCl 3 ) δ 122 (t, 3H, J=7.1 Hz), 3.65 (q, 2H, J=7.1 Hz);  13  C NMR (CDCl 3 ) δ 13.90, 34.09, 129.82, 146.45, 163.95; MS (EI) m/e 271 (M + ), 256, 243, 200, 172, 88. 
     EXAMPLE IV 
     6-n-Propyl-5H-Pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino-(2,3-C)(1,2,5)thiadiazole-5,7(6H) -dione ##STR7## 
     Following the procedure outlined in Example I, the title compound was prepared as an orange-red solid melting at 83°-84° C. in a yield of 4.07 g (55 percent of theoretical) by the reaction of 5.0 g (0.032 mol) of 3,4-dichloro-1,2,5-thiadiazole with 17.03 g (0.071 mol) of sodium sulfide followed by the addition of 6.0 g (0.033 mol) of 3,4-dichloro-N-n-propylmaleimide and the reaction thereof.  1  H NMR (CDCl 3 ) δ 0.91 (t, 3H, J=7.4 Hz), 1.63 (m, 2H), 3.50 (t, 2H, J=7.1 Hz);  13  C NMR (CDCl 3 ) δ 11.23, 21.89, 40.67, 138.75, 146.46, 164.18; MS (EI) m/e 285 (M + ), 256, 243, 200, 172, 88. 
     EXAMPLE V 
     6-n-Hexyl-5H-Pyrrolo (3&#39;,4&#39;:5,6)(1,4)dithiino-(2,3-C)(1,2,5)thiadiazole-5,7(6H) -dione ##STR8## 
     Following the procedure outlined in Example I, the title compound was prepared as an orange-red solid melting at 82°-83° C. in a yield of 5.85 g (56 percent of theoretical) by the reaction of 5.0 g (0.032 mol) of 3,4-dichloro-1,2,5-thiadiazole with 17.0 g (0.07 mol) of sodium sulfide followed by the addition of 8.07 g (0.032 mol) of 3,4-dichloro-N-n-hexylmaleimide and the reaction thereof.  1  H NMR (CDCl 3 ) δ 0.87 (m, 3H), 1.27 (bs, 6H), 1.57 (m, 2H), 3.52 (t, 2H, J=7.1Hz);  13  C NMR (CDCl 3 ) δ 14.20, 22.66, 26.48, 28.55, 31.39, 39.29, 129.89, 146.63, 164.28; MS (EI) m/e 327 (M + ), 270, 256, 243, 200, 172, 88. 
     EXAMPLE VI 
     6-Phenyl-5H-Pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino-(2,3-C)(1,2,5)thiadiazole-5,7 (6H) -dione ##STR9## 
     Following the procedure outlined in Example I, the title compound was prepared as a brown solid melting at 223°-225° C. in a yield of 3.25 g (85 percent of theoretical) by the reaction of 2.0 g (0.012 mol) of 3,4-dichloro-1,2,5-thiadiazole with 1.93 g (0.025 mol) of sodium sulfide followed by the addition of 3.0 g (0.012 mol) of 3,4-dichloro-N-phenylmaleimide and the reaction thereof.  13  C NMR (CDCl 3 ) δ 126.39, 128.16, 128.88, 129.63, 130.72, 145.91, 163.10; MS (EI) m/e 319 (M + ), 275, 190, 172. 
     EXAMPLE VII 
     6-(2-Phenethyl)-5H-Pyrrolo(3&#39;,4&#39;:5,6)(1,4)dithiino-(2,3-C)(1,2,5)thiadiazole-5,7(6H) -dione ##STR10## 
     Following the procedure outlined in Example I, the title compound was prepared as an orange-red solid melting at 176°-178° C. in a yield of 6.67 g (60 percent of theoretical) by the reaction of 3.7 g (0.024 mol) of 3,4-dichloro-1,2,5-thiadiazole with 1.6 g (0.048 mol) of sodium sulfide followed by the addition of 4.38 g (0.026 mol) of 3,4-dichloro-N-(2-phenethyl)maleimide and the reaction thereof.  1  H (CDCl 3 ) δ 2.92 (t, 2H, J=7.9 Hz), 3.79 (t, 2H, J=7.9 Hz), 7.27 (m, 5H);  13  C NMR (CDCl 3 ) δ 34.56, 40.38, 126.95, 128.73, 129.94, 137.24, 146.54, 164.03; MS (EI) m/e 374 (M + ), 256, 243, 200, 91. 
     The compounds of this invention are useful as antimicrobial additives, and they can be added to industrial products such as paints, inks, adhesives, soaps, cutting oils, textiles, and paper and pigment slurries and to styrene-butadiene latexes used for paper coatings. 
     The compounds are also useful as antimicrobial additives in such personal care products as hand creams, lotions, shampoos, and hand soaps. A further advantage of this invention is its cost-effectiveness for applications which need to have an antimicrobial continuously replenished, such as in cooling towers and pulp and paper mills. 
     As appreciated in the art, not all of the compounds disclosed herein are active at the same concentrations or against the same microbial species. That is, there is some compound-to-compound variation in antimicrobial potency and spectrum of antimicrobial activity. 
     The present invention is also directed to a method for inhibiting microorganisms which comprises contacting said microorganisms or habitat thereof with an effective amount of the compounds of this invention. 
     The antimicrobial compounds of this invention may be added directly to aqueous formulations susceptible to microbial growth, either undiluted or dissolved in inert diluents such as organic solvents such as glycols, alcohols, or acetone. They may also be added alone or in combination with other preservatives. 
     As used herein, the term &#34;microorganism&#34; is meant to refer to bacteria, fungi, viruses, algae, subviral agents and protozoa. 
     As used herein, the term &#34;antimicrobially-effective amount&#34; refers to that amount of one or a mixture of two or more of the compounds, or of a composition comprising such compound or compounds, of this invention needed to exhibit inhibition of selected microorganisms. Typically, this amount varies from providing 1 part per million (ppm) to 5,000 ppm by weight of the compound to a microbial habitat being contacted with the compound. Such amounts vary depending upon the particular compound tested and microorganism treated. Also, the exact concentration of the compounds to be added in the treatment of industrial and consumer formulations may vary within a product type depending upon the components of the formulation. A preferred effective amount of the compound is from 1 ppm to 500 ppm, more preferably from 1 ppm to 50 ppm by weight, of a microbial habitat. 
     The term &#34;microbial habitat&#34; refers to a place or type of site where a microorganism naturally or normally lives or grows. Typically, such a microbial habitat will be an area that comprises a moisture, nutrient, and/or an oxygen source such as, for example, a cooling water tower or an air washing system. 
     The terms &#34;inhibition&#34;, &#34;inhibit&#34; or &#34;inhibiting&#34; refer to the suppression, stasis, kill, or any other interference with the normal life processes of microorganisms that is adverse to such microorganisms, so as to destroy or irreversibly inactivate existing microorganisms and/or prevent or control their future growth and reproduction. 
     The antimicrobial activity of the compounds of the present invention is demonstrated by the following techniques. 
     The antimicrobial activity of the compounds of the present invention is set forth as the minimum inhibitory concentration (MIC) for the active compounds and is determined for nine (9) bacteria, using nutrient agar, and seven (7) yeast and fungi, using malt yeast agar. This determination is conducted using a one percent solution of the test compound prepared in a mixture of acetone and water. 
     Nutrient agar is prepared at pH 6.8, representing a neutral medium, and at pH 8.2, representing an alkaline medium. The nutrient agars are prepared by adding 23 g of nutrient agar to one-liter of deionized water. In addition, the alkaline medium is prepared by adjusting a 0.04 M solution of N-[tris-(hydroxymethyl)methyl]-glycine buffered deionized water with concentrated sodium hydroxide to a pH of 8.5. 
     Malt yeast agar is prepared by adding 3 g yeast extract and 45 g malt agar per liter of deionized water. The specific agar is dispensed in 30 mL aliquots into 25×200 mm test tubes, capped and autoclaved for 15 minutes at 115° C. 
     The test tubes containing the agar are cooled in a water bath until the temperature of the agar is 48° C. Then, an appropriate amount of the one percent solution of the test compound is added (except in the controls where no compound is added) to the respective test tubes so that the final concentrations are 500, 250, 100, 50, 25, 10, 5, 2.5, 1.0 and zero parts per million of the test compound in the agar, thus having a known concentration of test compound dispersed therein. The contents of the test tubes are then transferred to respective petri plates. After drying for 24 hours, the petri plates containing nutrient agar are inoculated with bacteria and those containing malt yeast agar are inoculated with yeast and fungi. 
     The inoculation with bacteria is accomplished by using the following procedure. Twenty-four hour-cultures of each of the bacteria are prepared by incubating the respective bacteria in tubes containing nutrient broth for 24 hours at 30° C. in a shaker. Dilutions of each of the 24 hour-cultures are made so that nine separate suspensions (one for each of the nine test bacteria) are made, each containing 10 8  colony forming units (CFU) per mL of suspension of a particular bacteria. Aliquots of 0.3 mL of each of the bacterial suspensions are used to fill the individual wells of Steer&#39;s Replicator. For each microbial suspension, 0.3 mL was used to fill three wells (i.e., three wells of 0.3 mL each) so that for the nine different bacteria, 27 wells are filled. The Steer&#39;s Replicator is then used to inoculate both the neutral and alkaline pH nutrient agar petri plates. 
     The inoculated petri plates are incubated at 30° C for 48 hours and then read to determine if the test compound which is incorporated into the agar prevented growth of the respective bacteria. 
     The inoculation with the yeast and fungi is accomplished as follows. Cultures of yeast and fungi are incubated for seven days on malt yeast agar at 30° C. These cultures are used to prepare suspensions by the following procedure. A suspension of each organism is prepared by adding 10 mL of sterile saline and 10 microliters of octylphenoxy polyethoxy ethanol to the agar slant of yeast or fungi. The sterile saline/octylphenoxy polyethoxy ethanol solution is then agitated with a sterile swab to suspend the microorganism grown on the slant. Each resulting suspension is diluted into sterile saline (1 part suspension to 9 parts sterile saline). Aliquots of these dilutions are placed in individual wells of Steer&#39;s Replicator and petri plates inoculated as previously described. The petri plates are incubated at 30° C. and read after 48 hours for yeast and 72 hours for fungi. 
     Table I lists the bacteria, yeast and fungi used in the MIC test described above along with their respective American Type Culture Collection (ATCC) identification numbers. 
     
                       TABLE I                                                     
______________________________________                                    
Organisms used in the Minimum                                             
Inhibitory Concentration Test                                             
Organism              ATCC No.                                            
______________________________________                                    
Bacteria                                                                  
Bacillus subtilis (Bs)                                                    
                       8473                                               
Enterobacter aerogenes (Ea)                                               
                      13048                                               
Escherichia coli (Ec) 11229                                               
Klebsiella pneumoniae (Kp)                                                
                       8308                                               
Proteus vulgaris (Pv)  881                                                
Pseudomonas aeruginosa (Pa)                                               
                      10145                                               
Pseudomonas aeruginosa (PRD-10)                                           
                      15442                                               
Salmonella choleraesuis (Sc)                                              
                      10708                                               
Staphylococcus aureus (Sa)                                                
                       6538                                               
Yeast/Fungi                                                               
Aspergillus niger (An)                                                    
                      16404                                               
Candida albicans (Ca) 10231                                               
Penicillium chrysogenum (PC)                                              
                       9480                                               
Saccharomyces cerevisiae (Sc)                                             
                       4105                                               
Trichoderma viride (Tv)                                                   
                       8678                                               
Aureobasidium pullulan (Ap)                                               
                      16622                                               
Fusarium oxysporum (Of)                                                   
                      48112                                               
______________________________________                                    
 
    
     In Tables II and III, the MIC values of the compounds of the present invention as compared to the MIC of a standard commercial preservative (with 1-(3-chloroallyl)-3,5,7-triaza-1-azoniaadamantane chloride as the active agent, and referred to in Tables II and III as &#34;STANDARD&#34;) are set forth for the bacteria organisms and yeast/fungi organisms which are listed in Table I. 
     
                                           TABLE II                                
__________________________________________________________________________
Minimum inhibitory Concentrations for Test Compounds                      
in Bacteria Species (in ppm)                                              
Compound                                                                  
        ORGANISMS                                                         
(Example No.)                                                             
        Bs  Ea  Ec  Kp  Pv  PRD Pa  Sc  Sa                                
__________________________________________________________________________
STANDARD                                                                  
pH 6.8  &lt;10 100 50  25  50  &gt;500                                          
                                &gt;500                                      
                                    50  25                                
pH 8.2  250 500 &gt;500                                                      
                    500 500 &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        &gt;500                              
(I)                                                                       
pH 6.8  &lt;10 250 100 100 50  500 500 100 100                               
pH 8.2  &gt;500                                                              
            &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        &gt;500                              
(II)                                                                      
pH 6.8  &lt;10 &gt;500                                                          
                50  250 25  &gt;500                                          
                                &gt;500                                      
                                    100 50                                
pH 8.2  250 &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        250                               
(III)                                                                     
pH 6.8  25  &gt;500                                                          
                50  500 50  &gt;500                                          
                                &gt;500                                      
                                    250 50                                
pH 8.2  100 &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        250                               
(IV)                                                                      
pH 6.8  &lt;10 &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        250 &gt;500                                          
                                &gt;500                                      
                                    500 50                                
pH 8.2  250 &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        50                                
(V)                                                                       
pH 6.8  &lt;10 &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        &lt;10                               
pH 8.2  25  &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        &lt;10                               
(VI)                                                                      
pH 6.8  &lt;10 &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        25                                
pH 8.2  100 &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        50                                
(VII)                                                                     
pH 6.8  &gt;500                                                              
            &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        &gt;500                              
pH 8.2  &gt;500                                                              
            &gt;500                                                          
                &gt;500                                                      
                    &gt;500                                                  
                        &gt;500                                              
                            &gt;500                                          
                                &gt;500                                      
                                    &gt;500                                  
                                        &gt;500                              
__________________________________________________________________________
 
    
     
                                           TABLE III                               
__________________________________________________________________________
Minimum Inhibitory Concentrations for Test                                
Compounds in Yeast/Fungi Species (in ppm)                                 
COMPOUND ORGANISMS                                                        
EXAMPLE NO.                                                               
         An  Ca  Pc  Sc  Tv  Ap  Fo                                       
__________________________________________________________________________
STANDARD &gt;500                                                             
             &gt;500                                                         
                 &gt;500                                                     
                     500 &gt;500                                             
                             &gt;500                                         
                                 &gt;500                                     
I        &lt;1  5   &lt;1  &lt;1  5   &lt;1  &lt;1                                       
II       &lt;1  &lt;1  &lt;1  &lt;1  &lt;1  &lt;1  &lt;1                                       
III      25  &lt;10 25  &lt;10 500 &lt;10 250                                      
IV       &lt;1  &lt;1  &lt;1  &lt;1  &lt;1  &lt;1  &lt;1                                       
V        25  25  25  25  50  25  25                                       
VI       &lt;10 250 &lt;10 100 500 &lt;10 250                                      
VII      100 &gt;500                                                         
                 &gt;500                                                     
                     250 &gt;500                                             
                             100 &gt;500                                     
__________________________________________________________________________
 
    
     The present invention is also directed to a method for inhibiting marine organisms. The term &#34;marine organisms&#34; is meant to include marine animals, such as barnacles, serpulid, bryozoa, oysters and hydroids, and marine plants, such as green algae and brown algae. The method for inhibiting marine organisms comprises contacting a surface exposed to a marine environment in which marine organisms grow with a marine antifouling effective amount of the compound of this invention. 
     As appreciated by those skilled in the art, not all of the compounds disclosed herein are active at the same concentrations or against the same marine organism species. That is, there may be some compound-to-compound variation in marine antifouling potency and spectrum of marine antifouling activity. Furthermore, the level of a specific compound&#39;s marine antifouling activity may be dependent on various factors including the specific materials with which the compound is formulated. 
     As used herein, the term &#34;marine antifouling effective amount&#34; refers to that amount of one or a mixture of two or more of the compounds of this invention needed to exhibit inhibition of selected marine organisms. Typically, this amount varies from providing 1 weight percent to 30 weight percent of the compound to a marine antifouling composition which is used to treat a surface exposed to a marine environment in which marine organisms live or grow. Such amounts vary depending upon the particular compound tested and marine organism to be treated. Also, the exact concentration of the compounds to be added in the preparation of industrial and consumer formulations may vary within a product type depending upon the components of the formulation. 
     A composition comprising a marine antifouling effective amount of the compound will also comprise an inert diluent which may be, for example, in the form of a paint. Particularly preferred are those paints having a vinyl resin binder such as, for example, a plasticized polyvinyl chloride or a polyvinyl chloride-polyvinyl acetate type. Preferably, the binders are formulated as latexes or emulsions. In a paint composition, the compound of the present invention is preferably used in an amount from 1 to 30 weight percent and, most preferably, from 10 to 25 weight percent. In addition to vinyl resin binder paints, epoxy and polyurethane binder paints containing the compound may also be useful. Coatings and films prepared from paints comprising the compound of the present invention typically remain substantially free from build-up of marine organisms for periods ranging from 3 to 12 months, depending upon the concentration of the compound and the thickness of the applied coating or film. 
     The term &#34;a surface exposed to a marine environment&#34; refers to a surface where a marine organism naturally or normally lives or grows. Typically, such a surface will be an area that is in continual or periodic contact with a marine environment such as an ocean or other body of water. Typical surfaces include, for example, a ship hull. 
     The marine antifouling activity of the compounds of the present invention is demonstrated by the following techniques. 
     Test panels are prepared from clear, rigid polyvinyl chloride film that is 0.381×10 -3  m thick and has one textured surface. The test panels are 0.1524 m by 0.1524 m squares that have 0.00635 m holes punched at corners on 0.127 m centers. A 0.102 square template, with a 0.067 m diameter hole at the center, is attached to the center of the textured surface of the test panels. 
     A candidate marine antifoulant compound (1.0 g) is stirred into a resinous latex binder (9.0 g). A portion of the compound/binder mixture (1.5 g) is added to the center of the test panel and uniformly spread over the circular area inside the template. 
     Water is added dropwise as needed to properly spread the compound/binder mixture. The template prevents the compound/binder mixture from spreading beyond the uncovered area. The test panel is allowed to sit for between 10 to 30 minutes until the edge of the spread compound/binder mixture has dried. The template is then removed. The test panel is then allowed to dry for 8 to 12 hours at room temperature. 
     Two test panels are prepared for each candidate marine antifoulant compound. Two control test panels are also prepared by only treating with the resinous latex binder. One test panel of each candidate marine surfactant compound is attached over a white background to the topside of an exposure support apparatus. The second test panel is attached over a black background to the underside of the exposure support apparatus. The exposure support apparatus is placed horizontally 0.0254 m under a marine surface with the white background topside facing up. The exposure support apparatus is exposed to the marine environment for both 6 and 10 weeks during which time the control test panels become substantially covered with mature marine organism growth on both the topside and underside exposures. 
     After being removed from the exposure support apparatus, each test panel is inspected and rated for marine organism growth on both the treated and untreated areas of the test panel. The marine organisms present on the treated and untreated areas are noted. The presence of algae spores and bacterial slime are noted but not included in rating each test panel. The test panels are rated on a scale from 10 (representing completely free of marine organism growth) to 0 (representing completely covered with marine organism growth). 
     In Table IV, the marine antifouling rating values for some of the active compounds of the present invention are set forth, as well as the ratings for control panels (with no marine antifouling compound and referred to as &#34;Control&#34;). 
     
                       TABLE IV                                                    
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Marine Antifouling Rating for Test Compounds                              
            Marine Antifouling Ratings                                    
            Top Panel  Bottom Panel                                       
            at indicated                                                  
                       at indicated                                       
            time in weeks                                                 
                       time in weeks                                      
Test Compound 6      10     16   6     10   16                            
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5H-Pyrrolo(3&#39;,4&#39;:5,6)-                                                    
              10     7      8    10    9    9                             
(1,4)dithiino-(2,3-C)-                                                    
(1,2,5)thiadiazole-5,7-                                                   
(6H)-dione                                                                
6-η-Propyl-5H-Pyrrolo-                                                
              9      7      7    9     7    7                             
(3&#39;,4&#39;:5,6)(1,4)-                                                         
dithiino-(2,3-C)(1,2,5)-                                                  
thiadiazole-5,7(6H)-                                                      
dione                                                                     
Control       6      3      --   0     0    --                            
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