EPOXYCHRYSANTHEMATES - 2-DIMENSIONAL NMR ANALYSES AND STEREOCHEMICAL ASSIGNMENTS

Two-dimensional NMR analyses of two pyrethroid insecticides, (S)-bioallethrin and (1R)-cis-phenothrin, and their diastereomeric 7,8-epoxy derivatives resulted in complete assignments of the H-1 signals of the acid moieties by COSY, long-range COSY, and NOESY measurements. The relevant C-13 signals of the six compounds were then assigned by C-H COSY experiments. Subsequent analyses of long-range C-H COSY spectra established that correlations between methyl carbons and adjacent methine protons involve those in a cis rather than a trans relationship, making this technique useful in assigning methyl resonances on the cyclopropyl and epoxy ring of related pyrethroids. The known stereochemical preference of Sharpless asymmetric epoxidation was used to assign the stereochemistry of the epoxy ring for the 7,8-epoxy-10-hydroxy derivatives of these two pyrethroids. Comparison of the NMR data of the 7,8-epoxy and 7,8-epoxy-10-hydroxy derivatives confirms that the configurations at C-7 of the principal 7,8-epoxy metabolites are R and S from microsomal oxidation of trans- and cis-chrysanthemates, respectively.