278 LECTURE XIII. 



with nitric acid. From alloxan they obtained a large number of closely 

 related compounds. We are indebted to Adolf Baeyer 1 for establishing 

 the constitution of alloxan and its closely allied derivatives. We will also 

 mention the discovery of A. Strecker, 2 that heating uric acid with concen- 

 trated hydrochloric acid in a sealed tube to 170 degrees, produces glycocoll, 

 carbon dioxide, and ammonia, water entering into the reaction: 



CsEUNA + 5 H 2 O = CH 2 . (NH 2 ) . COOH + 3 C0 2 + 3 NH 3 . 

 Uric acid Glycocoll 



From this fact, Strecker regarded uric acid as a glycocoll united with 

 cyanic acid, and assumed that the uric acid first broke down into glycocoll 

 and cyanic acid; the latter then being further decomposed into carbon 

 dioxide and ammonia: 



C 5 H 4 N403 = CH 2 . (NH 2 ) . COOH + 3 HCNO. 



This decomposition of uric acid was of great significance, because, using 

 it as a basis, Horbaczewski 3 next produced uric acid by fusing glycocoll 

 with urea at 220-230 C.: 



/NH 2 



3 CO + CH 2 . NH 2 . COOH = CsEW^Oa + 3 NH 3 + 2 H 2 O. 

 \NH 2 



On heating urea, ammonia is set free, cyanic acid also being formed, 

 which can then act further on the glycocoll. Another synthesis was accom- 

 plished by melting urea with tri-chlor-lactamid: 



/NH 2 



2 CO +C 3 C1 3 O 2 H 2 . NH 2 = H 2 O+NH 4 Cl + 2 HCl + Cs^N^s. 

 \NH 2 



These syntheses did not lead to an exact conception of the constitution of 

 uric acid. It was only through the carefully-planned, systematic inves- 

 tigations of Emil Fischer, that light was suddenly thrown on the whole 

 group of the purines and their derivatives. Not only does the entire chem- 

 istry of all the compounds of this group depend on his work, but also all 

 biological research in this field. 



We cannot at this place trace the development of all of Emil Fischer's 

 work, but will merely single out the points which are most important in 

 our study. 4 It is necessary in the first place to establish the relations 

 which exist between the various members of this group. Emil Fischer 

 based his work upon the relations of all the members of this group to 

 purine. He finally succeeded in obtaining purine itself, thus laying the 



1 Cf. his complete works, F. Vieweg & Sohn, Braunschweig, 1905, vol. i, p. 57. 



2 Ann. 146, 142 (1868). 



3 Monatsh. 3, 796 (1882) ; 6, 356 (1885). 



4 Cf. E. Fischer: Ber. 30, 549, 1839, 2226 (1897), and 31, 104 (1898). 



