2D NMR analysis of highly restricted internal rotation in 2-methylthio-3H-4-p-bromophenyl)-7-[(ortho- and para-substituted)-phenylthio]-1,5-benzodiazepines

The complete assignments of twelve 4-aryl-7-thioaryl-1,5-benzodiazepines H- 1 and C-13 spectra, performed with the use of high resolution variable solv ent and temperature 1D and 2D techniques (e.g. HOMOCOSY, NOESY, HMQC and HM BC), lead to the determination of conformational equilibria between two rot amers having the aromatic ring of the thioaryl oriented in a perpendicular or helical orientation toward the benzodiazepine ring. The restricted rotat ion was evaluated from the population of these conformers. (C) 2000 Elsevie r Science B.V. All rights reserved.