Studies of Multivalent Amino Acids and Pef’tides I. the Synthesis of Certain Tetravalent Amino Acids and Their Derivatives by Jesse P. Greenstein

In the study of the physicochemical properties of the proteins, it is often convenient to consider the behavior of the simpler ampholytes which reflect to some degree the properties of the more complex protein molecules. The investigation of simpler synthetic amphoteric models, usually amino acids and peptides, has illuminated such diverse properties of proteins as electrolytic dissociation (9, 13), apparent molal volume (7), solubility (6), and behavior toward enzymes (1). From the researches of Hcrricott and Northrop on pepsin (14) and of Freudenberg and Eyer (12), Jensen (15), and du Vigneaud (21) on insulin, it seems likely that the apparently specific propert.ies of many proteins may inhere in certain groups or linkages in the molecule. Many of these groups or linkages may be reproduced in synthetic models. Whether these groups may completely function dissociated from the colloid m0iet.y itself cannot as yet be answered. It would seem of interest, however, to prepare a series of complex synthetic. ampholytes and their derivatives and t.o examine several of their properties. These substances will resemble the prot,cin in bearing several free amino, carboxyl, and other characteristic groups upon a relatively small molecular area. The present communication is concerned with the synthesis of three new tetravalent amino acids: cy , y , 6-triamino-A~~a-pentenic acid, cr-aminotricarballylic acid, and E, r’-diaminodi (a-thio-ncaproic acid). The latter substance was further characterized by the formation of its e, c’-diguanido and ~,e’-diphenylurcido