Toward an analogue of the transition state of preD3-D3 isomerization: stereoselective synthesis of linearly fused 6-8-6 carbocyclic systems.

[reaction: see text] A stereoselective synthesis of 6-8-6 fused carbocyclic systems based on enol alkylation, ketone allylation, RCM, and Heck cyclization was developed to obtain compounds with a carbon framework that mimics the putative transition structure of the isomerization of previtamin D3 to vitamin D3.

Tandem RCM of dienynes for the construction of taxol-type carbocyclic systems.

[reaction: see text] Tandem ring-closing metathesis of hydrindanone dienynes allows access to taxosteroids, a new class of compounds that combine the [5.3.1] carbocyclic system of taxanes with rings C and D of the steroid skeleton.

RCM for the construction of novel steroid-like polycyclic systems. 1. Studies on the synthesis of a PreD3-D3 transition state analogue.

Natural and nonnatural polycyclic systems containing eight-membered carbocycles constitute a large class of compounds of importance in organic chemistry, biology, and medicine. Here we describe a new strategy by which complex polycyclic steroid-like systems can be constructed on the steroid CD framework, by a combination of RCM and Heck cyclizations. The method is exemplified by its application to the stereoselective synthesis of 6-8-6 fused carbocyclic systems that mimic the putative transition structure of the isomerization of previtamin D3 to vitamin D3.