Enantiomerically Pure Tetrahydropyrimidinones in Asymmetric Synthesis: Preparation of a Protected α-Methylasparagine Derivative and Corresponding Dipeptides

…, TA Ritsema, JP Konopelski

Index: Hopkins, Stephanie A.; Ritsema, Todd A.; Konopelski, Joseph P. Journal of Organic Chemistry, 1999 , vol. 64, # 21 p. 7885 - 7889

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Citation Number: 17

Abstract

Methyl ester 5a, available in enantiomerically pure form from the amino acid asparagine via a one-pot cyclization/protection sequence, followed by esterification, can be effectively deprotonated with LDA/DMPU/LiCl. Treatment with MeI affords the corresponding alkylated adduct in enantiomerically pure form, from which α-methylaspartic acid is obtained. Variation of the amine protection group allows for the isolation of a protected carboxylic acid/free ...