摘要:
A convenient method for the alpha-alkylation of (S)-asparagine with "self-regeneration of the stereogenic center" is described. The synthetic protocol involves stereoselective conversion of (S)-asparagine into enantiopure imino ether (2S,6S)-9, which is then alkylated with complete diastereoselectivity to give trans products 10-13 in good yields. Hydrolysis of these alkylated heterocycles is accomplished under mild acidic conditions to give the desired, enantiopure alpha-alkyl aspartic acids in excellent yields.