... (5) (a) A. M. Jeffrey, HJC Yeh, D. M. Jerina, RM DeMarinis, C. H. Foster, DE Piccolo, and G. A. Berchtold, J. Am. Chem. ... These conclusions regarding stereo- chemistry based on mechanistic considerations are sup- ported by NMR analysis (Table I). The NMR spectra of 4a, the ...