Microwave-enhanced solution coupling of the α,α-dialkyl amino acid, Aib

The difficult coupling of alpha -aminoisobutyric acid (Aib), during the synthesis of dipeptides (1-6), was carried out using PyBOP/HOBt and HBTU/HOBt reagents by application of the microwave energy in the presence of solvent. Room temperature, conventional heating (oil bath) and microwave irradiation of the reactions are compared. Synthesis by microwave irradiation gave the desired compounds in higher yields and in shorter reaction times than those obtained by conventional heating or at room temperature. (C) 2001 Elsevier Science Ltd. All rights reserved.