Coupling agent used in the synthesis of peptides: Belleau, Malek, J. Am. Chem. Soc. 90, 1651 (1968); Yajima, Kawatani, Chem. Pharm. Bull. 19, 1905 (1971); Sipos, Gaston, Synthesis 1971, 321. Preparation: Weinberg, US 3389142 and US 3452140 (1968, 1969, to Bristol-Myers). Has CNS depressant activity: Belleau, J. Am. Chem. Soc. 90, 823 (1968). Pharmacological studies: Martel et al., Can. J. Physiol. Pharmacol. 47, 909 (1969); Chang et al., Pharmacol. Res. Commun. 2, 63 (1970); Weissman, Muren, J. Med. Chem. 14, 49 (1971).