1. Contribution from the Departments of Biological Sciences and Chemistry, Boehringer Ingelheim (Canada) Ltd., Bio-Méga Research Division, Laval, Québec H7S 2G5, Canada, and Departments of Analytical Chemistry and Biology, Boehringer Ingelheim Pharmaceuticals Inc., Research and Development Center, 175 Briar Bridge Road, Ridgefield, Connecticut 06877