Synthetic approach to diterpene alkaloids. II Unusual reaction of angular nitromethyl group with diazomethane to give aldoxime.

Abstract

The 7-methoxyhydrophenanthrone (8) was synthesized from the 4a-nitromethylhydrophenanthrone (3) via nitration, reduction, and conversion of the resulting amino group to a methoxy group. On methylation of the intermediary phenol (7) with diazomethane, two products (9 and 10) were obtained along with the desired 8. The structures of these compounds having an aldoxime moiety were determined by physico-chemical methods. The mechanism of this unusual aldoxime formation from a nitromethyl group is discussed.

Diterpenoid alkaloids

“…Methylenation of a number of C,,-diterpenoid alkaloids containing a cis-diol system at C-7 and C-8, using diethoxymethane or aqueous formaldehyde in the presence of ptoluenesulphonic acid, has been reported. 178 Treatment of methyllycaconitine (189)…”