Treatment of a compound of structure 58 with a base, such as sodium hydride, and an alkylating agent, such as benzyl bromide, affords a compound of structure 29A. Alternatively, treatment of a compound of structure 58 with an aldehyde, for example acetaldehyde or paraformaldehyde, in the presence of a reducing agent, for example sodium cyanoborohydride or sodium (triacetoxy)borohydride, affords a