1. Natural Products Chemistry, Merck Research Laboratories, P.O. Box 2000, Rahway, New Jersey 07065, Merck and Co., Inc., Branchburg Farm, 203 River Road, Somerville, New Jersey 08876, Bio-Technical Resources, 1035 South 7th Street, Manitowoc, Wisconsin 54220, and Centro de Investigación Básica, Merck, Sharp & Dohme de Espana, S.A., Josefa Valcarcel 38, 28027 Madrid, Spain