Progress towards a Practical Total Synthesis of Calabar Alkaloids: Total Synthesis of (-)-Esermethole and (-)-Physovenol Methyl Ether from (3S)-1,3-Dimethyl-3-carboxymethyl-5-methoxyoxindole

Chemical resolution of the oxindoleacetic acid (7) with b ~c i n e in water yielded the acid (7a) of (3s)-absolute configuration.Acid (7a), in using conventional methods, was converted into nitrile pa), lactone (9a) and amides (lOa), and ( l l a ) respectively.Amide (lOa), on reduction with LAH in refluxing THF, directly yielded (-)-esermethole (12a), and amide ( l l a ) similarly gave (-)-N'-benzylnoresermethole (13a).Reduction of ester (6a) with LAH in refluxing THF yielded (-)-physovenol methyl ether (14a).