Synthesis, structural, conformational and biochemical study of some 3β‐acyloxytropan‐3α‐carboxylic acid hydrochlorides

Abstract

AbstractA series of 3β‐acyloxytropan‐3α‐carboxylic acid hydrochlorides have been synthesized and studied by 1H and 13C nmr spectroscopy, and the crystal structure of 3β‐(3,4,5‐trimethoxybenzoyloxy)tropan‐3α‐carboxylic acid hydrochloride 4c has been determined by X‐ray diffraction. The compounds studied display in methanol‐d4 the same preferred conformation. The pyrrolidine and piperidine rings adopt a flattened N8 envelope and distorted chair conformation; puckered at N8 and flattened at C3 respectively with the N‐substituent in equatorial position with respect to the piperidine ring. In all cases, there is only one mode (axial) of proton uptake at the piperidine nitrogen atom. These results are in close agreement with that found for compound 4c in the crystalline state. The inhibitory ability of the title compounds upon 3H‐GABA binding to sinaptosomal brain membranes is also reported.