Antibacterial action and chemical constitution in long-chain aliphatic bases.

The success of sulphanilamide as a chemotherapeutic agent encourages the investigation of other classes of compound for antibacterial properties. The compounds 'described in this paper were the long-chain amines, amidines and guanidines which had been shown by King, Lourie & Yorke [1938] to possess remarkable trypanocidal powers. They were chosen because they had a proved biological action, and also formed a convenient series of related compounds in which the effects of changes in constitution on antibacterial action could be observed. These compounds were generously placed at my disposal by Dr Harold King, to whom my grateful thanks are due. The drugs are listed below. Many of them have powerful antibacterial actions, and the effects of variations in the length of carbon chain, in the end groupings and in the bacteria studied are discussed. Drugs. These comprised the hydrochlorides of: 1. Diamines, general formula NH2. (CH2) . NH2, with n= 2, 6, 14, 16 and 18. 2. Diamidines, general formula NH2. (NH:)C. (CH2)n .C(:NH)NH2, with n= 8, 9, 10, 11, 12, 13, 14, 16 and stilbene diamidine. 3. Diguanidines, general formula NH2. (NH:)C.NH. CH2)n.NH.C(:NH) .NH2, with n=5, 6, 8, 10, 12, 14, 16 and 18. 4. Di-isothioureas, general formula NH2 . (NH:)C . S. (CH2)n . S . C . (:NH)NH2, with n=4, 6,8,11,12 and 16. + + 5. Di-quaternary ammonium compounds, general formula N(CH3)3. (CH2)f.N(CH3)3, with n= 8 and 14. 6. Monoamines, general formula H. (CH2), .NH2, with n=9, 12, 14, 16 and 18. 7. Monoamidines, general formula H. (CH2),. C(:NH) . NH2, with n= 15 and 17. 8. Monoguanidines, general formula H. (CH2)n.NH.C(:NH)NH2, with n=9, 14, 16 and 18. 9. Mono-quaternary ammonium compounds, general formula H. (CH2)" .N(CH3)3, with n=9 and 18. 10. Phenyl diguanide, phenyl guanidine, hexamethylene dipiperide, and octamethylene di-imino ether were inactive at the concentrations tested. For brevity, in the text, 18-methylene diamine, e.g., is referred to as 18-diamine, or as n= 18. It should be noted that since, by the above nomenclature, one carbon atom is included in the amidine group, the diamidines have n+2 and the monoamidines n+ 1 carbon atoms in an unbroken chain. The 12-diamidine, for example, is therefore compared with the 14-diamine, and the 15-amidine with the 16-amine.