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

Stephanie A. Hopkins, Todd A. Ritsema, and Joseph P. Konopelski*
Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064
J. Org. Chem., 1999, 64 (21), pp 7885–7889
DOI: 10.1021/jo9909296
Publication Date (Web): September 23, 1999
Copyright © 1999 American Chemical Society

Abstract

Abstract Image

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 amine derivative of α-methylasparagine. The utility of H-MeAsn-OMe is demonstrated in the formation of dipeptides.

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History

  • Published In Issue October 15, 1999
  • Received June 8, 1999

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