Saponification of amino ester 5(33) afforded the corresponding amino acid 6 in nearly quantitative yield. Acid 6 was treated with isobutylchloroformate and triethylamine, and the resulting mixed anhydride was reacted with diazomethane34 to provide high isolated yields of 7. Diazoketone 7 was treated with hydrochloric acid for simultaneous nitrogen deprotection and conversion to the chloromethylketone (CMK) intermediate 10. Alternatively, the N-Boc-protected bromomethylketone was prepared by treatment of 7 with stoichiometric quantities of 48% HBr in dichloromethane to provide 11. Another preparation of CMK intermediates that avoids the use of diazomethane was accomplished by the reaction of 5 with excess LDA and chloroiodomethane to afford 8 in moderate yields. A direct approach to oxymethylketone intermediate 9 was achieved by conversion of acid 6 to the corresponding Weinreb amide followed by treatment with the Grignard generated from benzyl chloromethyl ether.35