Not the alkoxycarbonylamino-acid O-acylisourea

Abstract

The reaction of equivalent amounts of N-benzyl-oxycarbonyl-L-valine and N,N′-di-isopropylcarbodi-imide in deuteriochloroform gives an equimolar mixture of the symmetrical anhydride of the N-protected amino-acid, N,N″-di-isopropylurea, and unchanged carbodi-imide and not the O-acylisourea adduct as reported in the literature.