1. Department of Biochemistry, McGill University, Montreal, Quebec, Canada, National Institute of Agricultural Biotechnology, 225 Seodun-Dong, Suwon 441-707, South Korea, Natural Products Research Institute, College of Pharmacy, Seoul National University, Seoul 151-742, South Korea, and Biotechnology Research Institute, NRC, 6100 Royalmount Avenue, Montréal, Québec, Canada H4P 2R2