Synthesis of terminal N-thiobenzoyl peptides by use of 4-substituted 2-phenylthiazol-5(4H)-ones as acylating agents for amino-acids and peptides. Optically-active 4-substituted 2-phenylthiazol-5(4H)-ones

Abstract

N(α)-Thiobenzamidoacylation of amino-acids and peptides is brought about by treatment with 4-substituted 2-phenylthiazol-5(4H)-ones in warm anhydrous acetic acid. A series of terminal N-thiobenzoyl peptides has been prepared in this way; the conditions are shown to be advantageous in analogous reactions with oxazol-5-ones. Corresponding N-substituted dipeptide esters are obtained by the reaction of carboxy-protected amino-acids with 2-phenylthiazolones in pyridine or in dichloromethane at room temperature.

Optically active 4-substituted 2-phenylthiazol-5(4H)-ones are obtained through cyclisation of N-thiobenzoyl-L-α-amino-acids with dicyclohexylcarbodi-imide; they are more susceptible to racemisation than the corresponding optically active oxazolones.