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.