Practical asymmetric synthesis of α-methylserine derivatives under mild phase-transfer conditions

The enantioselective methylation reaction of phenyloxazoline tert-butyl ester 5 using (R)-4b as a catalyst under mild phase-transfer conditions provides optically active α-methylserine derivatives in moderate yields with high enantioselectivity. Other α-alkylated serine derivatives are also achievable in high yields with high enantioselectivity by using catalytic amount of (R)-4b.