The effect of hydrophobicity upon the direct mutagenicity of N-acyloxy-N-alkoxyamides—Bilinear dependence upon LogP

[Display omitted] •Highly hydrophobic, direct-acting N-acyloxy-N-alkoxyamides in S. typhimurium TA100 have been tested.•A bilinear relationship has been established for 55 congeners giving an optimum LogP of 6.4.•Deviations of certain mutagens from this relationship have been explained in terms of groove exclusion or intercalation. N-Acyloxy-N-alkoxyamides 1 are direct-acting mutagens for which a bilinear QSAR has been established, which predicts with accuracy their activity in the Ames reverse mutation assay in Salmonella typhimurium TA100, based upon their hydrophobicity (LogP), reactivity (pKA of the carboxylic acid of the N-carboxyl group) and TAFT steric parameters. From activity data for 55 congeners and incorporating five mutagens bearing long-chain hydrocarbons on the alkoxyl and acyloxyl groups, designed for this study, a maximal LogPo, is found to be LogP=6.4. Mutagens with LogPLogPo undergo lipid entrapment which masks the DNA binding effect. The QSAR has been used to differentiate between lipophilicity and steric inhibition to groove binding in a series of outliers bearing large tert-butyl groups as well as to confirm the enhancement to DNA binding of the naphthalene moiety, which is shown to be equivalent to about 3.5LogP units.