First synthesis of the A/B ring of ouabain.

ABSTRACT

[reaction see text] The synthesis of the fully fuctionalized A/B ring of ouabain has been accomplished efficiently from commercially available starting materials. A key Robinson annulation allows for the building of the desired carbon framework in one high-yielding step. Directed epoxidation followed by selective epoxide opening furnished the final tetraol with the desired all-cis stereochemistry.