STEREOCONTROLLED APPROACH TOWARD VITAMIN-D METABOLITES - SYNTHESIS OF THE INHOFFEN-LYTHGOE DIOL

Steroids and their transformation products possessing modified side chains such as the molting hormones (e.g., ecdysones 1)1and the metabolites of vitamin D3(e.g., 2)2have spurred much research concerned with the synthesis of systems incorporating a functionalized side chain.3,4The vitamin D3problem is further complicated by conversion of the steroid nucleus into the seco system. Of the synthetic approaches, only Lythgoe's5and more recently Okamura's6directly construct the conjugated triene system. Thus, a strategy which produces a C,D unit incorporating the asymmetric center at C(20) (steroidal numbering) and which is suitably functionalized for elaboration into these biologically important systems as well as various analogues appears to represent a useful synthetic goal. We describe a synthesis of such a unit, e.g., 4, which, by conversion into the Inhoffen-Lythgoe diol 3, effects a formal total synthesis of both vitamin D3and some of its metabolites. © 1979, American Chemical Society. All rights reserved.