56 



SCIENCE 



[N. S. Vol. XLV. No. 1151 



the one form only. It may be, however, 

 that the reactions which Rosentlialer em- 

 ployed gave rise to both forms and that the 

 dextro form was destroyed as fast as it was 

 synthesized, through the action of the 

 emulsin. 



8. The most important contribution to 

 the subject of asymmetric syntheses in re- 

 cent years is that made by Bredig and 

 Fiske in 1912. Bredig and Fajans had 

 previously shown that the dextro and levo 

 camphor-carboxylie acids decompose with 

 different speeds in the presence of active 

 bases. When the reaction is carried out in 

 nicotine solution, for example, the speed of 

 decomposition of the d-acid is about 13 per 

 cent, greater than that of the Z-acid — results 

 that are similar to those of Dakin, who 

 studied the hydrolysis of mandelic esters 

 in the presence of lipase. "With this infor- 

 mation concerning the selective action of 

 the alkaloids in mind, Bredig and Fiske at- 

 tempted to utilize this property of alka- 

 loids in effecting asymmetric syntheses. 

 For this purpose they selected the same 

 reaction that Rosenthaler had used, namely, 

 the addition of hydrocyanic acid to ben- 

 zaldehyde, but substituted an alkaloid for 

 the emulsin. The results were decisive. 

 In the presence of quinine an excess of dex- 

 tro mandelic acid was formed, while quini- 

 dine gave an excess of the corresponding 

 levo compound. The alkaloid acted as a 

 catalytic agent since the results were ob- 

 tained by the use of relatively small 

 amounts of the bases. 



While all the methods for effecting par- 

 tial asymmetric syntheses so far discussed 

 differ somewhat in detail, yet they are all 

 fundamentally the same. In each case the 

 object has been to bring about an asym- 

 metric synthesis through the agency of the 

 forces exerted by a previously existing 

 asymmetric group. Now it is perfectly ra- 

 tional to suppose that in place of the forces 

 exerted by an asymmetric group, one 



might utilize the forces acting in a strong 

 .magnetic field or those exerted in either 

 plane or circularly polarized light. Ac- 

 cordingly, many attempts have been made 

 to employ these agencies. Pasteur himself 

 used the magnetic field as the active agent, 

 as did also Boyd (1896). Meyer, in 1903, 

 believing that the forces exerted in a mag- 

 netic field are not of the same character as 

 those exerted by an asymmetric group, at- 

 tempted to improve the experimeiit through 

 the combined influence of a magnetic field 

 9,nd polarized light. Henle and Haakh 

 (1908) concluded that a reaction that pro- 

 ,eeeds in the absence of light is not likely 

 to be influenced by the action of polarized 

 light. Accordingly they attempted to ef- 

 fect an asymmetric synthesis by the de- 

 composition of certain acids of the type of 

 malonie acid, through the action of light 

 in the presence of uranium compounds — a 

 reaction which will take place under the 

 conditions of the experiment, only in the 

 presence of light. In all of these investiga- 

 tions, however, no positive results were ob- 

 tained. 



The results of all the attempts to effect 

 either a partial or complete asymmetric 

 synthesis may be summed up as follows : in 

 so far as we are able to detect with instru- 

 ments at present constructed, an asymmetric 

 compound synthesized from its constituent 

 elements or from optically inactive com- 

 pounds is always obtained in the inactive 

 form. The optically active forms can be 

 prepared synthetically only through the 

 assistance of previously existing optically 

 active compounds. 



In making this general statement I am 

 disregarding the work of Stoklosa and his 

 co-workers (1913), who claim to have pre- 

 pared optically active sugars through the 

 action of ultra-violet light upon a mixture 

 of carbon dioxide and hydrogen in the pres- 

 ence of potassium hydrogen carbonate. 

 Stoklosa 's results are of the greatest im- 



