A novel 2H-azirin-3-amine as a dipeptide (Aib-Hyp) synthon

The synthesis of methyl(2S,4R)-4-(benzyloxy)-N-(2,2-dimethyl-2H-azirin-3-yl )prolinate (10), a novel 2H-azirin-3-amine ('3-amino-2H-azirine'), is descr ibed (Scheme 1). The reaction of methyl (2S,4R)-N-(20methylpropanoyl)-4-(be nzyloxy)prolinate (7) with Lawesson reagent gave methyl (2S.4R)-4-(benzylox y)-N-[2-(methylthio)propanoyl]prolinate (8) and consecutive treatment with COCL2, 1.4-diazabicyclo[2.2.2]octane (DABCO). and NaN3 led to 10. The use o f 10 as a building block of the dipeptide Aib-Hyp (Aib = 2-aminoisobutyric acid, Hyp = (2S,4R)-4-hydorxyproline) is demonstrated by teh syntheses of s everal model peptides (Scheme 2 and Table). The benzyl protecting group of the 4-OH function in Hyp in the model peptides has been removed in good yie lds.