Synthesis of 25-hydroxyprovitamin D3 and 25ξ,26-dihydroxyprovitamin D3

Abstract

The known C-22 aldehyde derived by degradation of ergosterol (in which the ring B diene system has been protected by reaction with 4-phenyl-1,2,4-triazoline-3,5-dione) reacts with the Grignard reagent derived from 4-chloro-2-methylbut-1-ene. The mesylate of the resulting C-22 alcohol undergoes reductive elimination, and the side chain double bond has been elaborated to give provitamins D₃ hydroxylated at C-25 or at C-25 and C-26. These provitamins are the precursors of known metabolites.