Cysteine condensation with glutamic acid

For the elongation of the chain starting from 11 toward the N-terminal group, direct condensation of the activated p-nitrophenyl esters of such amino acids as N-protected L-cysteine, L-glutamic acid, glycine, L-leu-cine, L-proline, L-serine, L-tyrosine, andL-valine with 2-acetamido-3,4,6-... 

Amino acids are practical chiral educts (chirons), and they also steer stereoselective reactions as catalysts. Phenylalanine-controlled aldol condensations with 2-dialkyl-cyclopenta-l,3-dione give just one enantiomer (Danishefsky and Cain, 1976) Intramolecular cyclization reactions of serine yield chiral P-lactams via an active hydroxyl amide and after protection of the amino group of serine. The addition of aldehydes to cysteine produces chiral thiazolidinecarboxylic acids in quantitative yield. Aspartic and glutamic acids have been converted to... 

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