1965 Volume 38 Issue 11 Pages 1831-1840
A cyclic hexapeptide, cyclo-pentaglycyl-L-lysyl hydrochloride (IIL), has been synthesized in an attempt to obtain fundamental information about the syntheses of cyclic peptides; it has also been subjected to the action of trypsin.
p-Methoxybenzyloxycarbonyltriglycyl-ε-benzyloxycarbonyl-L-lysylglycylglycine (XX) has been prepared by the saponification of the di-N-blocked hexapeptide ester which had been obtained by the condensation of p-methoxybenzyloxycarbonyltriglycyl-ε-benzyloxycarbonyl-L-lysine azide with the glycylglycine benzyl ester. XX has been converted to the relevant p-nitrophenyl ester by the action of di-p-nitrophenyl sulflte, and, after the removal of the p-methoxybenzyloxycarbonyl group with trifluoroacetic acid, the hexapeptide p-nitrophenyl ester has been transformed, by means of a large amount of pyridine, to the cyclic benzyl-oxycarbonyl-substituted hexapeptide. It has then been hydrogenolyzed in the presence of palladium black to furnish the desired product, IIL.
Several different synthetic methods for obtaining IIL have been adopted. However, they are not satisfactory with regard to the optical purity of the L-lysine residue or the yield.
It has been observed that IIL is completely hydrolyzed to pentaglycyl-L-lysine by trypsin. This appears to be the first example of how trypsin can hydrolyze a cyclic peptide. A smaller cyclic peptide, glycyl-L-lysine anhydride, could not be hydrolyzed.
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