Synthesis of α-methyl kainic acid by stereospecific lithiation–dearomatizing cyclization of a chiral benzamide

Stereospecific lithiation of N-α-methylbenzyl benzamides gives configurationally stable tertiary benzyllithiums which undergo a stereospecific dearomatizing cyclization with >99% retention of stereochemistry. The products are partially saturated isoindolinones which carry a new fully-substituted stereogenic centre. A ten-step sequence converts one of these products to the α-methyl analogue of kainic acid.