| Popis: |
Tricarbobenzoxy-L-arginine, as its sodium salt, was prepared in strongly alkaline medium via the carbobenzoxylation of L-arginine. This sodium salt, which was in fact a mixture of at least two different isomeric forms, was converted into a mixture of NαN,ω-dicarbobenzoxy-L-arginine and a single pure isomer of sodium tricarbobenzoxy-L-argininate upon treatment with boiling ethanol. Fractionation of these compounds, followed by acidification of the latter material, yielded pure tricarbobenzoxy- L-arginine wherein the basic properties of the guanido group were completely masked. The utility of this compound in the preparation of N-terminal arginine peptides was demonstrated upon its condensation with amino acid benzyl esters, via the mixed carbonic-carboxylic acid anhydride procedure, followed by catalytic hydrogenolysis of the condensation product. In addition, the N-carboxyanhydride procedure was utilized to effect the transformation of tricarbobenzoxy-L-arginine into NωN,ω -dicarbobenzoxy-L-arginine, and of NαN,ω -dicarbobenzoxy-L-arginine into Nω-carbobenzoxy-L-arginine, as well as the benzyl and methyl ester derivatives of the latter. All of these products are of potential value in the synthesis of C-terminal arginine peptides. In this connection, the esters of Nω-carbobenzoxy-L-arginine were employed in the synthesis of the benzyl and methyl esters of tricarbobenzoxy-L-arginyl-Nω-carbobenzoxy-L-arginine. © 1957, American Chemical Society. All rights reserved. |
