(1) Department of Studies in Chemistry, Central College Campus, Bangalore University, Dr. B.R. Ambedkar Veedhi, 560 001 Bangalore, India
Abstract:
An efficient conversion of Nα-(9–fluorenylmethyl)oxy]carbonyl (Fmoc) amino acid azides to the corresponding isocyanates using ultrasound is described. The Curtius rearrangement was accomplished using acid azides in toluene solution as well as solid powder at room temperature. All isocyanates synthesized have been obtained as crystalline solids and were characterized. Coupling of isocyanates with amino acid methyl ester hydrochloride salts in presence of N-methylmorpholine (NMM) resulted in Fmoc-protected dipeptidyl urea esters, which have been well characterized by 1H NMR, 13C NMR and mass spectrometry.