Approaches to the synthesis of 8-epi-vernolepin from germacrolides

Abstract

As part of our program aimed at the synthesis of bioactive products, the enantiospecific synthesis of 8-epi-vernolepin derivatives, starting from accessible germacrolides, was attempted. Synthesis of (+)-8-O-acetyl-1,2,11β,13-tetrahydro-8-epi-vernolepin (23) from (+)-salonitenolide (6) was performed in nine steps with an acceptable overall yield. On the other hand, the synthesis from (+)-stenophyllolide (5) presented several intrinsic difficulties and was discarded. (+)-Salonitenolide provides one of the most useful raw materials for the synthesis of (+)-vernolepin related compounds preserving its functionalization at C-8.