Selective synthesis of either enantiomer of alpha-amino acids by switching the regiochemistry of the tricyclic iminolactones prepared from a single chiral source

Preparation of l-alpha-amino acids was easily accomplished simply by exchanging the position of the lactone group of our recently reported chiral template 1 from C2 to C3. The new chiral template 7 was prepared in 54% overall yield over five steps from (1R)-(+)-camphor. Alkylation of iminolactone 7 afforded the alpha-monosubstituted products in good yields and excellent diastereoselectivities (>98%). Hydrolysis of the alkylated iminolactones furnished the desired l-alpha-amino acids in good yields and ee with nearly quantitative recovery of chiral auxiliary 4.