The dolastatins. 19. Synthesis of dolaisoleuine

Article abstract of DOI:10.1021/jo00086a034

The synthesis of dolaisoleuine as its tert-butyl ester (Dil-OBu(t)), a β- methoxy-γ-amino acid component of dolastatin 10, has been achieved employing as key step an aldol condensation between N-(benzyloxycarbonyl)-N-methyl- (S,S)-isoleucinal and tert-butyl acetate followed by O-methylation. The overall six-step reaction sequence to Dil proved to be convenient for routine preparation of this new amino acid and its stereochemical assignment as (3R,4S,5S)-N,O-dimethylisostatine.