摘要:
The total syntheses of decahydroquinoline alkaloids (+/-)-195A (pumiliotoxin C) and (+/-)-2-epi-195A are described. An unexpected, stereospecific epimerization of the C2 stereocenter of intermediate 6a occurred during its reduction. The isomerization resulted in ultimate production of 2-epi-195A. The stereochemical relationship of the C2, C4a, C5, and C8a stereocenters in 2-epi-195A is common to other decahydroquinoline alkaloids and gephyrotoxin. The 2-epi-195A synthesis demonstrated the viability of an N-Me group as a nitrogen protecting group. Alkaloid 195A was prepared in 5.0% overall yield by minor modification of the protocol established in the 2-epi-195A synthesis.