299 



in plants seem to prove beyond doubt, that exclusively d-glucose 

 and d-fructose are produced in vegetable cells, not their laevo- 

 gyratory antipodes. The direct production of optically active sub- 

 stances, therefore, seems to be the very prerogative of life; and 

 the cases are extremely rare, where racemic compounds are met 

 with in the living tissues. 



An exception of this is found in the case of pinene, extracted 

 from the leaves of Myristica fragrans Htn, which, according to 

 Van Romburgh 1 ), is sometimes laevogyratory, sometimes 

 dextrogyratory, - - it being impossible to tell under what particular 

 circumstances the one or the other of the antipodes is produced. 



In a recent publication 2 ) Hess and Weltzien try to de- 

 monstrate that, although in the animal organisms commonly a 

 real asymmetrical synthesis takes place, in plants, however, also 

 "symmetrical" synthesis may occur, especially in so far as con- 

 cerns the formation of alkaloids. Thus, coniine and methylconiine 

 are found in Conium maculatum in both the active forms or as 

 racemic compound. The atr opine obtained from Atropa belladonna, 

 although possessing in its molecule the asymmetrical carbon-atom 

 of the radical of tropic acid, is optically wactive. The same is 

 the case with laudanine and scopoline. They emphasize, that 

 direct experiments clearly show, that this optical inactivity cannot 

 be caused by autoracemisation during the process of separation 

 of these bases from the plants. 



Neuberg 3 ) found, that an inactive pentose was execreted by 

 the human organism in some cases of so-called "pentosuria", - 

 which, however, according to af Klercker, is a mixture of the 

 racemic compound with an excess of the laevogyratory component, 4 ) 

 while Elliot and Raper 5 ) find it more closely related to a 

 dextrogyratory ribose, than to a racemic arabinose, as Neuberg 

 thinks it to be. 



*) Private communication to the author by prof. P. van Romburgh. The 

 occurrence of d-asparagine in Fumaria, as mentioned in literature, seems to be 

 erroneous; cf.: H. Pringsheim, Zeits. f. physiol. Chemie, 65,89, (1910). 



2 ) K. Hess and W. Weltzien, Ber. d. d. Chem. Ges., 53, B, 119, (1920). 



3) C. Neuberg, His-Engelmann's Archiv, Physiol. Abth., (1902), p. 544; 

 idem, Der Harn, I, p. 370, (1911); Ber. d. d. Chem. Ges., 33, 2243, (1900). 



4) K. O. af Klercker, Deutsches Archiv. f. Klin. Medizin, 81, 284, (1912). 

 Cf. also: R. Luzzatto, Archiv. i. exper. Pathol. und Pharmakol., Suppl. Bnd., 

 (1908), p. 366. 



5) J. H. Elliot and H. S. Raper, Journ. Biol. Chem., 11, 211, (1912). 



