Synthesis and Use of 2H-Azirin-3-amines as Dipeptide Synthons

Abstract

The synthesis of the new 2H-azirin-3-amines ('3-amino-2H-azirines') 11, 20, 28, and 33 as dipeptide synthons is described. The reactions of the starting amides with Lawesson reagent gave the corresponding thioamides, and consecutive treatment with COCl2, 1,4-diazabicyclo[2.2.2]octane (DABCO), and NaN3 led to the desired products. It is shown that these 2H-azirin-3-amines can conveniently be used as building blocks of the dipeptides Aib-(Me)Axx (Axx = alanine, valine), Aib-Homoproline, and Iva-Pro in the synthesis of several model peptides. However, some limitations apply for the synthesis of such 2H-azirin-3-amines. The starting material for the azirine synthesis, the corresponding thioamides, cannot generally be synthesized, and the 2H-azirin-3-amines could not be obtained in all cases from the thioamides prepared.