Abstract3‐amino‐2H‐azirines undergo a number of ring opening reactions. The cleavage of the azirine‐N(1), C(3) double bond leads thereby to synthons which can be considered as amino acid equivalents. The reaction of 3‐amino‐2H‐azirines with carboxylic acids yields N‐acyl amino acid amides, which can be converted by a selective amide cleavage to the corresponding N‐acyl amino acids. 2‐Oxazolin‐5‐ones are intermediates of this amide cleavage. This reaction sequence has been used for the extension of peptide chains as well as for a number of heterocycle syntheses. Likewise, the described synthesis of cyclic depsipeptides and lactones by direct amide cyclization proceeds via 2‐oxazolin‐5‐one intermediates. The selective amide cleavage was also applied to a novel method for the resolution of enanti