Synthesis of 1alpha,25-dihydroxyvitamin D analogues featuring a S(2)-symmetric CD-ring core.

Three analogues of 1a,25-dihydroxyvitamin D(3) (calcitriol), featuring a trans-fused decalin C,D-core with local S(2)-symmetry, and possessing identical side-chain and seco-B,A-ring structures, have been synthesized starting from readily available (4aR,8aS)-octahydronaphthalene-1,5-dione (7). The very short sequences involve the simultaneous introduction of the side-chain and seco-B,A-ring fragments via Suzuki and Sonogashira coupling reactions. The analogues are devoid of relevant biological activity.