Cd → BCD → Abcd

Abstract

The starting CD intermediates for the various total syntheses outlined in this chapter and in Chapter 7 are often the same or quite analogous. Historically, a large effort has been expended in the preparation of such material, both in the context of steroid synthesis and, recently, as a goal unto itself. A discussion of the pathways developed for the synthesis of CD intermediates has been included at this point such that later, when the individual total synthetic schemes are presented, it will be unnecessary to outline the preparation of the starting materials, except in those cases where unique pathways have been developed.Most of the early synthetic plans started with appropriate naphthalene derivatives which in turn gave rise to D-homosteroids. For example, Johnson's estrone synthesis started with decalin-l,5-dione (3, Scheme 12-1) which had earlier been prepared from 1,5-dihydroxynaphthalene (58%) [1], By modifying the previously employed conditions to include Raney nickel hydrogénation at elevated temperatures and pressures in a basic ethanolic solution, it was possible to obtain a mixture of diols, 2 (stereochemistry undetermined), which, without purification, could be oxidized to a mixture of eis and trans diketones 3 [2], The yield for this conversion (l-»3) was 55% and, for synthetic purposes, the mixture 239 O OH J Φ-,ύ^.