Abstract
The Schiff base (I) from glycine tert-butyl ester and benzaldehyde was treated with lithium diisopropylamide to give the corresponding α-carbanion. Alkylation of the α-carbanion with benzyl or butyl halide followed by removal of benzylidene group yielded phenylalanine or norleucine tert-butyl ester (IIa or IIb), accompanied by dialkylated product (IIIa or IIIb). The Schiff base (IV) from alanine tert-butyl ester and (-)-men-thone (VI) was also treated as above to furnish α-methylphenylalanine or α-methyl-β-(3, 4-dimethoxyphenyl) alanine tert-butyl ester (Va or Vb) in 21 or 24% asymmetric yield.
