The preparation of (R)- and (S)-(E)-but-2-enyl-t-butylphenylphosphine oxides and their enantiospecific conversion into enantiomeric hydrindenones related to vitamin D

The individual enantiomers of (E)-but-2-enyl-t-butylphenylphosphine oxide have been prepared, and the lithiated carbanions of each undergo completely stereoselective conjugate addition with 2-methylcyclopent-2-enone to generate enolates, which upon reaction with 4-chlorobut-3-en-2-one and subsequent reduction have been converted into the corresponding enantiomers of hydrindenones suitable for conversion into vitamin D analogues and their enantiomers.