Cyclization of polyenes. 49. Cyclization of epoxyneocembrene derivatives to secotrinervitanes
摘要:
Four stereoisomers of epoxyneocembrene derivatives 5-8 were treated with BF3.OEt2 as potential model reactions for the proposed biogenesis of secotrinervitane-type diterpenoids (Scheme I). Two of them (5 and 6) afforded secotrinervitane derivatives, while the remaining isomers 7 and 8 gave no cyclization products (Table I). The natural product, secotrinervitene-2-beta,3-alpha-diol (2a) was synthesized from 5 in dl-form.