Steroids and related natural products. Part XCII. Conversion of canarigenone[14-hydroxy-3-oxo-14β-carda-4,20(22)-dienolide] into periplogenin [3β,5,14-trihydroxy-5β,14β-card-20(22)-enolide]

Abstract

Oxidation of canarigenone (IV) by peroxy-acid gave the 4β,5β-epoxide (V), which was reduced by chromium(II) acetate to the 5β-hydroxy-3-ketone (VI). Selective reduction of this with Urushibara nickel A led to periplogenin (Ia). The epoxy-ketone (V) was also prepared from canarigenin (VII). Since digitoxigenin (III) had previously been converted to canarigenin (VII) and canarigenone (VI) the synthetic route to periplogenin constituted a formal total synthesis.