facile synthesis of (r,r) and of (r,s) tricarballylic acid anhydride and imide derivatives

The diastereomeric mixture of (R)-2-(methoxycarbonylmethyl)-N-(R)-1-(1-phenylethyl) succinimide 11s and (S)-2-(methoxycarbonylmethyl)-N-(R)-1-(1-phenylethyl) succinimide 11a was synthesized by reaction of 2-(carboxymethyl)succinic anhydride 6 with (R)-(α)-methylbenzylamine in dry THF/room temperature/24 hrs. The diastereomeric mixture of 1-[(R)-(α)-Methylbenzylamideformyl)]propane-2,3-dicarboxylic acid anhydride 9s and 1-[(R)-(α)-methylbenzylamideformyl)]propane-2,3-dicarboxylic acid anhydride 9a was isolated as an intermediate under the reaction conditions. This diastereomeric mixture 9s/9a was also prepared by a different route via reaction of 1-(chloroformyl)propane-2,3-dicarboxylic acid anydride 12 with (R)-(α)-methylbenzylamine in the presence of DMA at 0oC for 24 hrs.