Hitherto unknown synthesis of 19-nor-vitamin D compounds

摘要

A convergent synthesis of 19-nor-vitamin D compounds, specifically 19-nor-1 alpha ,25-dihydroxyvitamin D3, is disclosed. The synthesis can also readily be utilized for preparing other 1 alpha -hydroxylated 19-nor-vitamin D compounds. The key step in the synthesis is a suitable application of Lythgoe's procedure i.e. a Horner-Wittig reaction of the lithium anion of a phosphine oxide with a Windaus Grundmann ketone to give, after any necessary deprotection, the desired 19-nor-vitamin D compound.