Coupling reagent for which the rates of reaction with various nucleophiles are sufficiently different to permit a genuine "one-step" coupling of carboxylic acids with amines: Synthesis, 547 (1980). Particularly suitable for coupling N-alkyl amino acids: J. Org. Chem., 51, 3350 (1986). For discussion of strategies for one-step coupling in synthesis of amides, see: Synthesis, 413 (1984), and of the scope and limitations of the reagent in peptide coupling, see: Int. J. Pept. Prot. Res., 29, 574 (1987); J. Org. Chem., 55, 2895 (1990). For use in the direct selective 5'-acylation of nucleosides by carboxylic acids, (without 3'-protection), see: Tetrahedron, 44, 229 (1988). For high yield dehydration of carboxylic acids to anhydrides, see: Synthesis, 616 (1981). Also used in macrolide cyclization: J. Am. Chem. Soc., 104, 6818 (1982), and in formation of acyclic esters: Synth. Commun., 14, 515 (1984). The mixed anhydride formed with carboxylic acids adds to imines to give ?-lactams: Synthesis, 63 (1982). These are also formed in high yield by cyclization of ?-amino acids: Bull. Korean Chem. Soc., 12, 457 (1991).
