Thiocarboxylates, 0-methyl thioacylation

Methyl thiocarboxylates are very suitable for the V-thioacylation of V-unprotected amino acids. Thus, shaking a heterogenous mixture of PhCSOMe in ether and the amino acid in aq. NaOH gives g(X)d yields of V-thiobenzoylated material. Using (9-alkyl thiocarboxylates of amino acids (2 R = R NHCHR ), the approach has been extended to synthesize endothiopeptides such as (5) formation of imidates may interfere with the desired process. The reaction has been carried out in water/THF using NazCOj or as shown in equation (3). ... 

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