SYNTHESIS OF SOME NEUTRAL, WATERSOLUBLE CARBODIIMIDES AND THEIR USE IN THE FORMATION OF PEPTIDE BONDS

Two symmetrical (10a, 10b) and three unsymmetrical carbodiimides (10c, 10d, 10e) were synthesiz-ed from tris(β-methoxymethyl)ethylamine (1), bis(methoxymethyl)methylamine (2), and tris(methox-ymethyl)methylamine (3). They are neutral and readily soluble in many organic solvents including pe-troleum ether and possess sufficient solubilities in water except 10a which is less soluble. Their relativeabilities as condensing agent in the formation of peptide bonds were tested preliminarily by couplingphthalyl glycine and glycine ethyl ester in chloroform as well as in water and can be related to the stericeffects exerted by methoxymethyl-substituted alkyl residues with the order: tertiary>primary>secondary.1,3-Bisbis(methoxymethyl)methyl] carbodiimide (10b) is promising as an all-soluble condensing agentfor the formation of peptide linkage and by its ready availability.