A process for preparing a compound of formula (A), (B) or (C): wherein P is H, CH3 or a hydroxyl protecting group; X is O, a protected ketone, OH, a protected hydroxyl group or H; Y is OH, a protected hydroxyl group or H; W is C(CH3)2OH, (CH3)(C(CH3)3)OH or COCH3; Z is C2-C10 alkyl or C2-C10 arylalkyl; and is a single bond or a double bond, is disclosed. The process includes reductive alkylation in the presence of hydrogen and a reductive alkylation catalyst.