^a Faculty of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Kumamoto, 862, Japan

^b Niigata College of Pharmacy, 5-13-2 Kamishinei-cho, Niigata, 950-21, Japan

^c Biotech Research Laboratories, 3 Taft Court, Rockville, MD 20850, U.S.A.

^d Department of Surgery, Duke University Medical Center, Durham, NC 27710, U.S.A.

^e Boston Biomedica, Inc., 375 West Street, West Bridgewater, MA 02379, U.S.A.

^f Natural Products Laboratory, Division of Medicinal Chemistry and Natural Products, School of Pharmacy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7360, U.S.A.