• Reagent for peptide coupling: J. Org. Chem., 44, 5000 (1979). Has the advantage over N,N'-Dicyclohexylcarbodiimide, A10973 in solid phase peptide syntheses that the urea by-product is more soluble in organic solvents and hence more readily separated from the polymer support. For peptide reagents, see Appendix 6.