Reagent for peptide coupling. Reaction proceeds via the anhydride of the acid component: J. Am. Chem. Soc., 90, 823, 1651 (1968); Int. J. Pept. Prot. Res., 26, 493 (1985). For activation of ɑ -hydroxy acids, see: Tetrahedron Lett, 40, 3435 (1999) . Also used for the mild esterification of alcohols, e.g. for introduction of the levulinate protecting group: Tetrahedron Lett., 23, 2615 (1982). For a useful esterification technique applicable to primary, secondary and tertiary alcohols, see: J. Org. Chem., 60, 7072 (1995).
