287 



believed by Pasteur, may not be supposed He drew 

 attention to the tat t that artificial synthesis also is evidently 

 one-sided on as there an- several asymmetric ai -bun-atoms 



in the attacked molecule. Indeed, if this were not true, the pro- 

 HIJ; condensation oiglycerose, formaldehyde, or acroleinc-bromide, 

 would necessarily lead to all sixteen possible isomeric aldoses and 

 nil the eight ketoses. Instead of this, besides ot-acrose, only a single 

 raceinic//t - .msY is obtained; and this, clearly proves that there is a cer- 

 tain preferential direction in the synthesis of these sugars under 

 these conditions. The same must be the case in the important 

 cyanhydrine-reaction ; .when a certain dissymmetry of the reacting 

 molecule pre-exists, the addition of HCN no longer occurs in a 

 symmetrical way. Thus in using mannose, the one antipode of manno- 

 heptonic acid l ) was obtained to an amount of 87%, whereas of 

 the other no appreciable quantity was found. 



With this evidence Fischer undoubtedly for the first time 

 brought clearly to the fore the essential features of "asymmetric" 

 synthesis in general. Natural synthesis in the living organism 

 takes place in a one-sided way, because it occurs under collaboration 

 of optically active molecules; the dissymmetrical arrangement of 

 such molecules taking part in the chemical processes has a guiding 

 influence, and thus a single optically active compound of a whole 

 set of isomerides is formed in greater quantity than the others. 



However, it would perhaps be preferable to draw attention 

 more particularly to the differences in speed in the process of 

 synthesis of the isomeric substances. For the possibility of life- 

 processes is at bottom, - - from a chemical point of view - - a 

 question of the mutual regulation of reaction-velocities: the orga- 

 nism cannot stop its physiological functions for a single moment. 

 It produces and consumes continually, and these processes of 

 synthesis and metabolism, of waste and production, must all go 

 on with definite, well regulated mutual velocities, if the life- 

 process is to be carried on at all. A state of completed "reaction- 

 equilibrium" is never reached therefore: only a kind of apparent 

 "dynamical constancy". Now it is most probable that other iso- 

 merides than those found in the vegetable cells, are formed 

 simultaneously in the synthetic process, but with an incomparably 

 smaller speed. It is possible that there are exceedingly small 



) E. Fischer, Ber. d. d. Chem. Ges. 22. 370. (1889). 



