166 CHEMISTRY OF THE PROTEIDS CHAP. 



which is isomeric with the oxy-amino-acids, C 6 H 13 N0 3 , described by 

 E. Fischer and Tiemann l and Neuberg and Wolff. 2 



In the e-amino-a-oxy-caproic acid, the NH 2 -radical may be substi- 

 tuted by a halogen (e.g. by Jochem's method), and the resulting com- 

 pound be reduced to a-oxy-w-caproic acid, CH 3 . [CH 2 ] 3 CHOH. COOH, 

 and in this way a relationship be established to glucosamic acid and 

 to glucose. 



Analogous to the conversion of di-amino-propionic acid into glyceric 

 acid is the change which alanin, or mono-amino-propionic acid, undergoes 

 in passing through the body, for it gives rise to lactic acid, 3 which, as a 

 tautomer of gly eerie-aldehyde, is closely related to glucose. Embden 

 and Salomon 4 have further shown that in dogs suffering from pan- 

 creatic diabetes, alanin produces a very marked and quickly occurring 

 increase in the amount of sugar in the urine. The same authors in 

 a later paper 5 show in addition that lactic acid, glycocoll, and 

 asparagin increase the amount of sugar, while urea does not. That 

 asparagin leads to sugar -formation was, however, first observed by 

 Nebelthau. 6 



The two most promising observations made recently in connection 

 with the formation of sugars from albumin, and reversely the con- 

 version of sugars into aminated radicals occurring in the albumin 

 molecule, are those of Skraup and Wohlgemuth who discovered the 

 di-amino-poly-carboxylic acids. (See pp. 44 to 45.) 



The two most promising observations made recently in connection 

 with the formation of sugars from albumin, and reversely the con- 

 version of sugars into aminated radicals occurring normally in the 

 albumin, are the discovery of oxy - diamino - dicarboxylic acids by 

 Skraup 7 (see p. 44), and the conversion of grape-sugar into methyl- 

 imidoazol by Windaus and Knoop. 8 



The oxy-amino-acids serin, oxy-prolin, tetraoxy-amino-caproic 

 acid, oxy-amino- suberic acid, trioxy-diamino-dodecanoic acid, and oxy- 

 amino-succinic acid occupy a position midway between the sugars 

 and the amino-acids. The following oxy-acids have been synthetised : 



1 Fischer and Tiemann, Ber. d. deutsch. chem. Ges. 27. 144 (1894). 



2 Neuberg and Wolff, ibid. 35. 4015 (1902). 



3 Neuberg and Langstein, Verhand. physiol. Ges. Berlin, 1903. See also Neuberg 

 and Silbermann, Ber. d. deutsch. diem. Ges. 37. 339 (1904). 



4 G. Embden and H. Salomon, Nofmeister's Beitrdge, 5. 507 (1904). 



5 Ibid. 6. 63 (1904). 



6 Nebelthau, Munchener'mediz. Wochenschr. 1902, p. 917. 



7 Zd. H. Skraup, Zeitschr.f. physiol. Chem. 42. 274 (1904) ; and Wiener Monatshefte, 

 26. 245 (1905). See also J. Wohlgemuth, Ber. d. deutsch. chem. Ges. 37. 4362 (1904). 



8 A. Windaus and F. Knoop, Ber. d. deutsch. chem. Ges. 38. 1166 (1905) ; and in 

 ffofmeister's Beitrdge, 6. No. 8. 



