2 OPTICAL ACTIVATION 



Brenwr 1 has split up inactive malic acid into its active com- 

 ponents by means of cinchoiiine ; and Lewkowitsch 2 has decom- 

 posed mandelic acid into its active isomers by different methods. 

 The reverse of the method used Pasteur was employed by 

 Ladenburg* in the synthesis of conine. Here a racemic base 

 a- normal propyl piperidine, prepared by the reduction of 

 a- allyl piperidine, was split up into its antipodes by means 

 of an active acid. E. Fischer 4 in his researches in the sugar 

 group has split up many compounds by the foregoing methods 

 of Pasteur. 



It is well known that the majority of the properties of 

 antipodes are the same; for example, both generally react at 

 the same rate. When, however, antipodes unite with another 

 optically active body, they lose their antipode character and 

 acquire 'different solubilities, rates of reaction, etc. Much use 

 has been made of this in separating a racemic body into its opti- 

 cally active components. Eor instance, on account of the different 

 rates at whi'-h an active body reacts with a racemate, it is 

 possible to obtain a product which shows optical activity, by 

 stopping the reaction before completion. In this manner 

 Markwotd and Meth 5 effected a partial separation of r- maii- 

 delic acid by 1- meiitliylamme, the amicle being formed by 

 the reaction. The converse of this method has been used 

 successfully by McKenzie and Thompson, who prepared 

 optically active products by submittinr the partially racemic 

 esters, formed by the complete esterification of different acids 

 externally compensated by optically active alcohols, to fractional 

 hydrolysis with an inactive base. 



An asymmetric synthesis of an active compound from a 

 symmetric substance, whereby an .optically active solvent should 



1. Bremer, G. J. W.: Ber. d. deutsch. chem. Ges., 13, 351, (1880). 



2. Lewkowitsch, J.: Ber. d. deutsch. chem Ges., 16, 1573, (1883). 



3. Ladenburgr, A.: Ber. d. deutsch. chem. Ges., 19, 429, and 2518. 



(9881) 



4. Fischer, E.: ibid. 23, 2114. (1890). 



5. Markwald. W., and Meth, R.: ibid., 38, 801. (1905). 



6. McKenzie, A., and Thompson, H. B.: Trans. Chem. Soc., 91, 789, 

 (1907). 



