Diastereoselective Electrophilic Amination of Chiral l-Benzoyl-2,3,5,6-tetrahydro-3-methyl-2-(l-methyIethyl)pyrimidin-4(lH)-one for the Asymmetric Syntheses of alpha-Substituted alpha,beta-Diaminopropanoic Acids

摘要

The chiral compounds(R)-and(S)-l-benzoyl-2,3,5,6-tetrahydro-3-methyl-2-beta-methylethyl)pyrimidin-4(1H)-one((R)-and(S)-l),derived from(R)-and(S)-asparagine.respectively,were used as convenient starting materials for the preparation of the cnantiomerically pure alpha-alkylated(alkyl=Me,Et,Bn)alpha,beta-diamino acids(R)-and(S)-11-13.The chiral lithium enolates of(R)-and(S)-1 were first alkylaled.and the resulting diasteroisomeric products 5-7 were aminated with 'di(tert-butyl)azodicarboxylate'(DEAD),giving rise to the diastereoisomerically pure(>=98%)compounds 8-10.The target compounds(R)-and(S)-11-13 could then be obtained in good yields and high purities by a hydrolysis/hydrogenolysis/hydrolysis sequence.