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, The New York Botanical Garden, Bronx, New York 10458, and Department of Soil, Crop and Climate Sciences, University of the Free State, P.O. Box 339, Bloemfontein, 9300 South Africa