Viacheslav A. Petrov1, Giuseppe Resnati. 1. DuPont Central Research and Development, P.O. Box 80328, Wilmington, Delaware 19880-0328, and C.N.R.-Centro Studio Sostanze Organiche Naturali, Dipartimento Chimica, Politecnico, 7, via Mancinelli, I-20131 Milano, Italy.