Calciferol and its relatives. Part XIV. Total synthesis of des-AB-cholestane-8β,9α-diol 2{1β-[(1R)-1,5-dimethylhexyl]-7aβ-methyl-trans-perhydroindane-4β,5α-diol}

Abstract

In a new route to 1-substituted trans-3a,6,7,7a-tetrahydro-7a-methylindan-2-ones, a 1-monoester of 4-methyl-cyclohex-3-ene-1,trans-2-diol is subjected to two successive Claisen-type rearrangements to give, in a stereospecific manner, derivatives of 1-methylcyclohex-3-ene-1,trans-2-diacetic acid, which are then cyclised. Applied to the 1-benzoate (16) and methyl orthodihydrocitronellate (17), the method provides a direct synthesis of the 1,5-dimethylhexylindanone (20), and thence of the title diol (22), required for use in the total synthesis of tachysterol₃ and precalciferol₃.