CHAP. III.] CONSTITUTION AND SYNTHESIS OF LEUCINE. 



237 



and albumi- 

 noid bodies. 



aside, the leucine crystallises out. By dissolving the crystals in spirits of 

 wine and recrystallising the substance is still further purified 1 . 



According to Zollikofer 2 the ligamentum nuchae of the ox most 

 readily furnishes leucine. One part by weight of the tissue is boiled 

 for three hours with a mixture of 2 parts of sulphuric acid and 3 

 parts of water. No increased yield of leucine is obtained if the 

 boiling be -further prolonged. The product may be treated exactly 

 as described in the first process. 



Quantities of ^ e yields of leucine when various bodies were 

 leucine 1 obtain- treated by the sulphuric acid method were as follows 

 ed from various (Erlenmeyer and Schoffer 8 ): Lig. nuchae 35 45/ 

 albuminous of its weight ; blood-fibrin 14 % ' muscle 18 / albu- 

 min 10%: horn 10 / . Nencki 4 by the same process 

 obtained from gelatin 1'5 2 % 



Constitution and Synthesis of Leucine. 



Leucine is an ami^o-caproic acid. There are theoretically eight 

 possible caproic acids (C 6 H 12 2 ), of which seven have already been 

 prepared, and corresponding to these eight acids, thirty-one possible 

 isomeric amido-caproic acids or leucines. For reasons which space 

 will not permit us to discuss, the leucine which is obtained by the 

 decomposition of the albuminous or albuminoid bodies can only be 

 a derivative of one or other, or of both, of two of the isomeric caproic 

 acids : to wit normal caproic acid or isobutylacetic acid. Further, 

 we are acquainted with facts which prove that in either case the NH 2 

 group must occupy the a-position. Briefly, the constitution of, what 

 we may term, the physiological normal leucine must be represented 

 by one or other of the two appended formulae. 



i. n. 



CH 3 CH 3 



OH, 

 GIL 



CH 



a) CH- 



(a) 



NH 



COOH 



a-Amido-normal caproic acid. 



a-Amido-isobutylaeetic acid. 



1 The description of this process is taken verbatim from Drechsel's ' Anleitung 

 zur Darstellung physiologisch-chemischer Praparate, &c.' The method of separating 

 and purifying leucine from tyrosine given is that employed by Hlasiwetz and Haber- 

 mann (' Ueber die Proteinstoffe,' Ann. d. Chem. und Pharm., Vol. CLXIX. p. 150). 



2 Zollikofer, 'Beitrage zur Kenntniss d. elastisch. Gewebes.' Annal. d. Chem. u. 

 Pharm., Vol. LXXXII. (1852), p. 162180. 



3 Erlenmeyer and Schoffer, quoted by Maly, op. cit. p. 209. 



Nencki, Journ. /. prakt. Chemie, N. F. Vol. xv. pp. 390398. 



