Abstract:
Compounds of the following formula and a method for their preparation are disclosed: ##STR1## wherein Ar is substituted or unsubstituted phenyl, R, R&#39; and R&#34; may be similar or dissimilar and are each selected from the group consisting of lower alkyl of from 1 to about 5 carbon atoms. The compounds of this invention are useful as antimicrobial agents.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to antimicrobial compounds and, more particularly, to compounds useful for the inhibition of microorganisms such as bacteria and fungi in media likely to be infected with such microorganisms. 
     Phenylnitrocyclobutane derivatives similar to the compounds of the present invention are known in the art. Such compounds are described, for instance, by Kuehne, M. E., et al., J. Org. Chem. 30, 4280-4284 (1965) and by Brannock, K. C., et al., J. Org. Chem. 29, 801 (1964). Such compounds are prepared by reacting an enamine with nitrostyrene, thereby yielding compounds represented by the following structural formula: ##STR2## wherein Ar is phenyl and the R 1 , R 2  and R 3  substituents depend upon the particular enamine employed in the reaction. 
     In the compounds disclosed in the aforementioned references, the carbon atom to which the nitro group is bonded also has a hydrogen atom bonded thereto. It has been found that such compounds possess no significant antimicrobial activity, e.g. antibacterial or antifungal activity, and, furthermore, they are not sufficiently stable to normal conditions of temperature and humidity to be useful as commercial products. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, there is provided a compound of the formula ##STR3## wherein Ar is substituted or unsubstituted phenyl, and R, R&#39; and R&#34; are similar or dissimilar and are each selected from the group consisting of lower alkyl of from 1 to about 5 carbon atoms. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The compounds of the present invention are prepared by reacting an appropriate enamine with a β-alkyl-β-nitrostyrene, or a derivative thereof according to the following reaction: ##STR4## The phenyl group may be unsubstituted or may be substituted in one or more positions with such substituents as halogen, e.g. chloro, bromo, iodo, fluoro, hydroxy, lower alkoxy, e.g. having from 1 to about 5 carbon atoms, or alkyl, e.g. having from 1 to about 5 carbon atoms. R, R&#39; and R&#34; are lower alkyl from 1 to about 5 carbon atoms. 
     The reactants may be mixed together without a solvent or may be dissolved in a suitable solvent which does not react deleteriously with the reactants or the product. Suitable solvents include alcohols, such as methanol or ethanol; ethers, such as ethyl ether or tetrahydrofuran; aliphatic hydrocarbons, such as hexane or heptane; and aromatic hydrocarbons, such as benzene or toluene. The reaction is advantageously conducted at an elevated temperature, e.g. above about 40° C. and preferably from about 60° C. to about 100° C., for a time sufficient to effect a substantial production of the product. Reaction times in the range of from about 1 hour to about 15 hours, preferably from about 6 hours to about 12 hours, are generally employed. 
     The reaction product may be recovered and purified by conventional means. Recrystallization from hexane and methanol have been used to purify the product, and further purification may be effected by column chromatography. The compounds produced by the reaction may exist in several diastereomeric forms, and the chemical formulae depicted herein are intended to represent all of such forms. The present invention is not limited to compounds of any particular diastereomeric form but embraces all diastereomers or mixtures thereof. 
     The nitrocyclobutane derivatives of the present invention have been found to possess a wide spectrum of antimicrobial activity. That is, the compounds are effective for controlling or inhibiting the growth of microorganisms, including bacteria and fungi, in media infected with such organisms. 
     The compounds of this invention may be used to preserve or disinfect products subject to microbiological degradation. The amount of compound added to such products will depend on the nature of the product and the type and degree of microbial infection. The compounds are useful for preserving products such as pharmaceuticals, cosmetics, starch pastes, dispersion dyes, cutting and drilling oils, leather tanning solutions, paints and the like. The compounds are generally employed in such products in antimicrobially effective concentrations. Such concentrations generally range from about 0.01% to about 3% by weight of the product and preferably fall within the range of from about 0.1% to 1% by weight. 
     This invention is further illustrated by the following examples which are not intended to be limiting. 
    
    
     EXAMPLE I 
     A solution of 1-phenyl-2-nitropropene (4.89 g, 0.03 mole) and 1-(1-piperidyl)-2-methylpropene (4.59 g, 0.033 mole) was stirred at 70°-80° C. for ten hours. The solution was protected from moisture with a drying tube. The solution solidified as it was cooled to room temperature. The solid was slurried with 60 ml of hot hexane and, on cooling, yielded 6.2 g of product melting at 102°-104° C. Infrared and nuclear magnetic resonance spectra of the product were consistent with the structure of 1-(4-nitro-3-phenyl-2,2,4-trimethylcyclobutyl)piperidine. The product had the following elemental analysis: Found: C-71.5%, H-8.6%, N-9.3%, O-10.6%; Calculated: C-71.4%, H-8.5%, N-9.2%, O-10.9%. 
     EXAMPLE II 
     The product from the experiment of Example I was subjected to antimicrobial testing. The compound was dissolved in acetone and serially diluted to concentrations ranging from 10 ug/ml to 10,000 ug/ml. These solutions were diluted with agar media in petri dishes to provide concentrations of 1000, 500, 250, 100, 50, 10 and 1 ug of compound per ml of media. The agar media employed were Trypticase Soya Agar pH-7.6 for antibacterial tests and Sabourauds Agar pH-5.3 for antifungal tests. The petri dishes were swirled to mix the compound into the agar, and controls were prepared containing no test compound. 
     Test microorganisms, which were stored on standard agar slant cultures, were streaked on the surface of the agar media using sterile cotton swabs or sterile wire loops. The microorganisms against which the compound was tested are listed in Table I. 
     The petri dishes were inverted and incubated at about 37° C. for a sufficient time period (18-48 hours) to establish good growth on the control media. The inhibition endpoints were reported as those concentrations of test samples between which growth was totally inhibited. There was growth at the lower reported concentration, but no growth at the next higher concentration. 
     The inhibition endpoints determined for the nitrocyclobutane derivative of Example I in the antibacterial and antifungal tests are given in Table I. The results demonstrate that the compound possesses wide spectra antimicrobial activity. 
     
                       TABLE I______________________________________                Inhibition                EndpointOrganism             (μg/ml)______________________________________Staphylococcus aureus                50-100Streptococcus fecalis                100-500Streptococcus hemolyticus                100-500Escherichia coli     50-100Pasteurella pseudotuberculosis                50-100Pseudomonas aeruginosa                50-100Shigella dysenteriae 50-100Aspergillus niger    10-100Penicillium sp.      10-100Aspergillus fumigatus                10-100Candida albicans     10-100______________________________________ 
    
     EXAMPLE III 
     The experiment of Example I was repeated in all essential details except that 1-phenyl-2-nitroethene was substituted for 1-phenyl-2-nitropropene. The resulting compound was identified to be 1-(4-nitro-3-phenyl-2,2-dimethylcyclobutyl)piperidine by infrared and nuclear magnetic resonance spectroscopy and by elemental analysis. The product was observed to decompose in a sealed container at room temperature over a period of several weeks. The product of the experiment was subjected to antimicrobial screening as described in Example II. The results of the screening, which are shown in Table II, indicate that the compound possesses no significant antibacterial or antifungal activity. 
     
                       TABLE II______________________________________Organism           Inhibition Endpoint (μg/ml)______________________________________Staphylococcus aureus             Greater Than 1000Streptococcus fecalis             Greater Than 1000Streptococcus hemolyticus             Greater Than 1000Escherichia coli  Greater Than 1000Pasteurella pseudotuberculosis             Greater Than 1000Pseudomonas aeruginosa             Greater Than 1000Shigella dysenteriae             Greater Than 1000Aspergillus niger Greater Than 1000Candida albicans  100-500Penicillium sp.   500-1000Aspergillus fumigatus             Greater Than 1000______________________________________ 
    
     EXAMPLE IV 
     The experiment of Example I is repeated in all essential details except that 1-(1-piperidyl)-2-methylbutene is substituted for 1-(1-piperidyl)-2-methylpropene. 1-(4-Nitro-3-phenyl-2-methyl-2-ethylcyclobutyl)piperidine should be recovered. 
     EXAMPLE V 
     The experiment of Example I is repeated in all essential details except that 1-(1-piperidyl)-2-ethylpentane is substituted for 1-(1-piperidyl)-2-methylbutene, and 1-(4-chlorophenyl)-2-nitrobutene is substituted for 1-phenyl-2-nitropropene. 1-(4-Nitro-3-(4-chlorophenyl)-2-propyl-2,2-diethylcyclobutyl)piperidine should be recovered.