1. Program for Collaborative Research in Pharmaceutical Sciences, m/c 877, College of Pharmacy, the University of Illinois at Chicago, 833 S. Wood Street, Chicago, Illinois 60612, Institute of Chemistry, National Center for Science and Technology, Nghia Do, Tu Liem, Hanoi, Vietnam, and Cuc Phuong National Park, Nho Quan District, Ninh Binh Province, Vietnam