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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 jV"V,"-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 TV-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 V-carboxyanhydride procedure was utilized to effect the transformation of tricarbobenzoxy-L-arginine into Ar"Ar"-dicarbobenzoxy-L-arginine, and of V".V"-dicarbobenzoxy-i.-arginine into V"-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 V"-carbobenzoxy-L-arginine were employed in the synthesis of the benzyl and methyl esters of tricarbobenzoxy-L-arginyl-V"-carbobenzoxy-L-arginine.

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