A New 2 H ‐Azirin‐3‐amine as a Synthon for 2‐Methylaspartate

The synthesis of a novel 2,2‐disubstituted 2 H ‐azirin‐3‐amine 3a as a building block for racemic Asp(2Me) is described. This synthon contains an ester group in the side chain. The reaction of 3a with thiobenzoic acid and the amino acid Z‐Val‐OH yielded the racemic monothiodiamide 10a and the dipeptide 11 as a mixture of diastereoisomers, respectively ( Scheme 2 ). In 11 , each of the protecting groups was removed selectively ( Scheme 3 ). First attempts toward the preparation of enantiomerically pure synthons for Asp(2Me) with a chiral auxiliary group in the side chain are described. Synthons 3b with a 1‐(naphthalen‐1‐yl)ethyl ester group and 3c with a menthyl ester group were prepared and reacted with thiobenzoic acid to form monothiodiamides 10b and 10c ( Scheme 2 ). However, the diastereoisomers of the synthons 3b and 3c could not be separated by chromatography.