[Studies on the efficient syntheses of the drug metabolites]

This review summarizes our recent findings in the syntheses of drug metabolites. The metabolites of Grepafloxacin (1) and OPC-14117 (10) were prepared from the common intermediates (5) and (21), respectively. Moreover, treatment of 10 with a model P450 system led to a benzyl alcohol derivative (11) in one step. OPC-31260 (22) was efficiently N-dealkylated using several metalloporphyrins with oxidants to afford three metabolites (23-25). In addition, I succeeded in obtaining the metabolite (23) in high yield from N-oxide (26) not only as an oxygen donor but also as a substrate, there after, in the model P450 system. Optically active metabolites of OPC-29030 (27) were prepared by enzyme-catalyzed enantioselective transesterification of racemic sulfinyl metabolites. On the other hand, a chiral 1,1'-bi-2-naphthol derivative (38a) was found to be an efficient asymmetric acylating agent for a secondary alcohol (36) which is a valuable intermediate for preparing optically active metabolites of 22. Furthermore, metabolites (45) and (47) of OPC-21268 (44) were prepared using SmI2-induced cyclization and oxidative decarboxylation with Pb(OAc)4 as key steps, respectively.