Studies in the aza-Cope reaction: a formal highly enantioselective synthesis of tryprostatin B

The BF3–Et2O induced rearrangement of N-phthaloyl-1-(3,3-dimethylallyl)-l-tryptophane methyl ester proceeds without significant loss of its optical integrity to provide its 2-(3,3-dimethylallyl) isomer, a key intermediate in the synthesis of tryprostatin B.