156 THE PROTEIN SUBSTANCES. 



Tryptophane was first prepared in a pure form by HOPKINS and 

 CoLE, 1 and they considered it as skatolaminoacetic acid. After ELLIN- 

 GER showed that skatolcarbonic acid (SALKOWSKI) and skatolacetic 

 acid (NENCKI) were indolacetic acid and indolpropionic acid respectively, 

 and after the synthesis of d-Z-tryptophane by ELLINGER and FLAM AND, 2 

 the nature of this substance as indolaminopropionic acid was established. 



By condensation of /3-indplaldehyde with hippuric acid ELLINGER and FLAMAND 

 prepared the azlactone (lactimide) : 



N 



.C 6 H 5 +2H 2 0. 



CO O 



On boiling with dilute caustic soda, with the taking up of water, the sodium 

 salt of indoxyl-a-henzoylaminoacrylic acid, 



C 8 H 6 N.CH : C.NH.COC 6 H & 

 COONa 



is obtained, from which by reduction and splitting off of the benzoyl group by 

 the action of sodium alcoholate the tryptophane is obtained : 



C 8 H 6 N.CH : C.NH.COC 6 H 6 



| +H 2 +H 2 =C 8 H 6 N.CH 2 .CH.NH 2 -r-C 6 H 5 COOH. 



COOH COOH 



The trytophane formed in digestion is /-tryptophane, which is laevoro- 

 tatory in aqueous solution (HOPKINS and COLE). Racemic cW-trypto- 

 phane has also been obtained by digestion in certain cases by ALLERS 

 and NEUBERG, this is probably formed from the Z-tryptophane (ABDER- 

 HALDEN and L. BAUMANN 3 ), which very readily undergoes racemization. 

 f Tryptophane crystallizes in silky rhombic or six-sided leaves. It 

 does not have a sharp melting-point, and according to the rapidity of heat- 

 ing melts at 252, 273 and 289, according to various authorities. 

 Tryptophane is readily soluble in hot water, difficultly soluble in cold 

 water, and only slightly soluble in alcohol. The solution of d-l-trypto- 

 phane has a faintly sweetish taste, and /-tryptophane a faintly bitter taste. 

 The statements as to the optical behavior of tryptophane differ some- 

 what, which, according to ABDERHALDEN, is probably due to the readiness 

 with which it undergoes racemization. According to ABDERHALDEN 

 and L. BAUMANN, 4 at 20 C. the aqueous solution has a rotation of 



1 Journ. of Physiol., 27. 



2 Ellinger, Ber. d. d. Chem. Gesellsch., 37 and 38. With Flamand, ibid., 40, and 

 Zeitschr. f. physiol. Chem., 55. 



3 R. Allers, Biochem. Zeitschr., 6; C. Neuberg, ibid., 6; Abderhalden and Baumann, 

 Zeitschr. f. physiol. Chem., 55. (Literature on the specific rotation.) 



4 See Abderhalden and Baumann, Zeitschr. f. physiol. Chem., 55 (literature). 



