Open AccessMolecular structure of opiate alkaloids. Part II. Crystal structures of 4-methylhomobenzomorphan hydrobromide (I)and 4,12β-dimethylhomobenzomorphan (II)
Author(s) -
A. G. Michel,
G. Evrard,
Bernadette Norberg,
Eugène Milchert
Publication year - 1988
Publication title -
canadian journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.323
H-Index - 68
eISSN - 1480-3291
pISSN - 0008-4042
DOI - 10.1139/v88-284
Subject(s) - chemistry , lone pair , ring (chemistry) , intermolecular force , molecule , substituent , crystallography , stereochemistry , nitrogen atom , nitrogen , organic chemistry
The two title compounds belong to the family homobenzomorphans. Their analgesic properties are comparable to morphine but without inducing physical dependence. This work presents the results of X-ray diffraction and NMR studies to elucidate the conformational properties particular to this class of compounds. More specifically, the spatial orientation of the nitrogen lone-pair are compared to those observed for other related molecules. The two molecules adopt the same L-shaped structure and the 16β-methyl substituent present in the second molecule does not modify this structure. Although very different in both structures, the intermolecular interactions do not alter the molecular conformation. The nitrogen lone pair is oriented away from the benzene ring and its orientation is conserved in solution, as proven by nmr studies. The main conclusions are that the seven-membered ring shows very specific conformational properties and that the lone-pair orientation is predictable, according to the position of the nitrogen in the ring. Finally, it is concluded that correlations between the nitrogen lone-pair orientation and the analgesic activity have to be reconsidered.