SYNTHESIS AND STRUCTURAL AND CONFORMATIONAL STUDY OF 3-ALPHA-METHOXYCARBONYL-3-BETA-(3',4',5'-TRIMETHOXYBENZAMIDO)-N8-SUBSTITUTED NORTROPANES

Two 3-alpha-methoxycarbonyl-3-beta-(3',4',5'-trimethoxybenzamido)-N8-substituted nortropanes have been synthesized and studied by IR, H-1 and C-13 NMR spectroscopy and the crystal structure of 3-alpha-methoxycarbonyl-3-beta-(3',4',5'-trimethoxybenzamido) 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.