Center for Heterocyclic Compounds, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200, USA Chemistry Department, King Abdulaziz University, Jeddah 21589, Saudi Arabia E-mail : katritzky@chem.utl.edu Fax : 352-392-9199 Manuscript received 16 July 2013, accepted 17 July 2013 Efficient synthesis of S-acyl homocysteine allow chemical ligation (S-acyl to N-acyl transfer) via 6-membered cyclic transition state. The results represent the first example of successful isopeptide ligation starting from S-acyl homocysteine.