Asymmetric Solid-Phase Synthesis of (R)-α-Amino Acid Derivatives

Significance

The Merrifield resin-bound glycine imine tert-butyl ester 2 was prepared by treatment of 1 with a trimethyl orthoformate solution of glycine tert-butyl ester hydrochloride and triethyl­amine. The enantioselective alkylation reactions of 2 with several alkyl bromides in the presence of the chiral phase-transfer catalyst (chiral PTC) gave the corresponding alkylated products 3. α-Substituted N-benzoyl tert-butyl esters 4 were obtained by hydrolysis of 3 with 1 N HCl followed by benzoylation of the resulting amines in 61-80% yields with 93-99% ee (9 examples).