March 1966
UIOLOGICllL ~ C r P I V I T 1 E SO F
CHLOliAhIPHENICOL ANALOGS BY h I I c a o ~ 1 . 4I p-SCH9 > p-I > p-Br m-N02 > p-OCHo > p-C1 > p-i-C3H7 > p-S02CH3> p-NH2, where the p-SCH,, p-S02CH,, and m-N02 analogs are incongruent with the Hansch equation. The individual inhibitory constants, k , , can be used to predict quantitatively the rate of E. coli growth in any admixture of analogs, e.g., k = ko 2ik,[I], and clearly demonstrate that, in this series, dose effects are additive with respect to rates.
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The interest in correlating substituent constants and partition coefficients with biological activity as evidenced by the recent publications of Hansch arid coworkers2 has shown the vital need for the quantitative and precise evaluation of the biological activity of various subktituted compounds. Only when such data are available can the niodels for such correlations be adequately tested and modified. The complaint'" is legitimate that there is a severe limitation o n the number of adequate examples in the literature where a particular compound has been modified with a, wide variety of substituents and where these comFounds have been tested under a standard set of conditions to yield quantitative results. I n fact, an outstanding exception is consideredza to be a study of the action of chloramphenicol analogs on microorganisms by the serial-dilution method where the accuracy of the determinations was f25%.3 The need for quantification at a higher order of accuracy is readily apparent when parameters are to be correlated in the intermediate ranges of activities, ie., 25-10070 of the most active analog. (1) This is number IT' in a series entitled Kinetics and Mechanisms of Action of hntibiotics on Microorganisms. The previous publications in this series were (a) E. R. Garrett and &I. R. W. Brown. J . P h a r m . Pharmacol., 16, 185T (1963); (b) M. R. W. Brown and E. R. Garrett, J . P h a r m . Sei., 63, 179 (1964); (c) E. R. Garrett a n d G. H. Miller, ibid., 64, 427 (1965). ( 2 ) (a) C. Hansch, R. AI. Muir, T. Fujita, P . P. Maloney, F. Geiger, and BI. Streich, J . A m . Chem. Soc., 85, 2817 (1963); (b) C. Hrtnsch and T. Fujita, ibid., 86, 1616 (1964); IC)C. Hansch and A. R. Steward, J . M e d . Ckem.. 7 , 691 (1964); (d) T. Fujita, J. I a a s a , and C. Hansch. J . A m . Chem. Soc., 86, 5175 (1964); (e) J. Iwasa, T . Fujita, and C . Hansch, J . .Wed. Ckem., 8 , 150 (1965). (3) A l . N. Shemyakin, 11. S. Iiolosov, 11. AI. Levitov, I
