Selective synthesis and structural elucidation of S-acyl- and N-acylcysteines

Abstract

(Chemical Equation Presented) N-(Acyl)-1H-benzotriazoles 6a-f react with L-cysteine 5 at 20°C to give exclusively (i) N-acyl-L-cysteines 8a-e in the presence of triethylamine in CH3CN-H2O (3:1), but (ii) S-acyl-L-cysteines 7a-e in CH3CN-H2O (5:1) in the absence of base. Structures 7b, 7d and 8b, 8d are supported by 2D NMR spectroscopic methods including gDQCOSY, gHMQC, gHMBC, and 1H-15N CIGAR-gHMBC experiments. The structure of compound 8d was also supported by single-crystal X-ray diffraction. © 2009 American Chemical Society.