Synthesis and structural and conformational study of 3α-methoxycarbonyl-3β-(3′,4′,5′-trimethoxyb enzamido)-N8-substituted nortropanes

Abstract

Two 3α-methoxycarbonyl-3β-(3′,4′,5′-trimethoxyb enzamido)-N8-substituted nortropanes have been synthesized and studied by IR, 1H and 13C NMR spectroscopy and the crystal structure of 3α-methoxycarbonyl-3β-(3′,4′,5′,-trimethoxy benzamido) tropane (IIa) has been determined by X-ray diffraction. The compounds studied display in deuterochloroform the same preferred conformation. The pyrrolidine and piperidine rings adopt a flattened N8 envelope and distorted chair conformation, puckered at N8 and markedly flattened at C3, with the N-substituent in equatorial position. This conformation seems to be governed by an intramolecular hydrogen bond. The crystal structure of IIa shows a complex hydrogen bonding network. Concerning the tropane skeleton, the X-ray results for IIa are quite similar to those found for compounds IIa,b in CDCl3 solution. Some spectroscopy data of the precursor amidonitriles are also described. © 1992.