Relaxation pathway analysis by 1H spin-lattice relaxation and nuclear Overhauser effect difference measurements. Application to a reassignment of the 1H nmr spectrum of strychnine and to the determination of the structure and stereochemistry of some strychnine sulfonic acids

Abstract

The ¹H relaxation pathway analysis of strychnine and some strychnine sulfonic acids has been carried out by spin-lattice relaxation and nuclear Overhauser effect difference measurements. Some previously reported ¹H chemical shifts and coupling constants for strychnine are shown to be in error. New assignments for positions 15, 17, 18, and 20 have been made. Proposed sites of substitution of the sulfonic acids have been verified, and the previously undetermined stereochemistry of one of the acids has been established.