The Introduction of Oxygen Functions into the B Ring in Synthetic Diterpenes

Abstract

In many synthetic sequences aimed at preparing highly oxygenated diterpenes, the manipulation of oxygen functionalities in the B ring can be critical. For instance, while elaborating syntheses of taxodione¹, we were confronted by the necessity of shifting the C.7 carbonyl (as in i) to the C.6 position (as in v). Of the many carbonyl shifts available, Matsumoto and his co-workers² have successfully used the following:

This is reduced to only two practical steps since neither the alcohol ii nor the epoxide iv is isolated. In our hands (on three different products) this Matsumoto shift' has been disappointing, especially the epoxidation step³ which was both slow and un-rewarding, so we have examined system at ically several alternate schemes which effect this carbonyl shift or achieve its equivalent.