292 



benzoy I- formate; however his results were as negative as those of 

 Cohen and Whiteley. 



Because of technical difficulties Fischer and Slimmer's 

 attempts to produce a one-sided cyanhydrine-synihesis with helicine : 



H 



C=0 (C 2 H 3 0) 4 C 6 H 7 5 



C 6 H 4 ^ , and with tetracetyl-helicine: >0 



X OC 6 H U 5 C 6 H 4 -Cg) 



had at last to be given up. In the last case the apparently 

 positive result was produced by the admixture of a strongly 

 optically active condensation-product in the oxy-phenyl-ethyl-carbinol 

 finally obtained. 



Scholtz 1 ) started with N-methyl-a,-pipecoline, and combined 

 laevogyrate amyl-iodide with it; the unattacked base however 

 proved to be absolutely inactive. 



In 1 904 Marckwald, 2 ) starting with inactive methyl- ethyl- 

 malonic acid, obtained finally an optically active valeric acid in 

 the following way. 



He prepared from the first compound the acid brucine-salt, the 

 solution of which was evaporated and the less soluble product 

 separated from it. This was then heated to 170 C, carbon-dioxide 

 driven off, and the brucine removed from the residue. 



The valeric acid thus obtained was a mixture of the racemic 

 and 10% laevogyrate acid. Tymstra 3 ) found that the final 

 product yields more than 25% excess of laevogyraie acid if heating 

 is done in vacuo; the temperature must not be higher than 

 100 120 C. in that case. Cohen and Patterson 4 ) are right 

 in their criticism when they contend that the first stage of 

 Marckwald's process is in reality nothing but Pasteur's 

 second fission-method of racemoids. 



They compare the reaction with the case in which ordinary 

 racemic acid was first resolved by brucine, and then the less soluble 

 tartrate obtained was reduced to brucine-malate : in this case, after 

 saponification, undoubtedly an optically active malic acid should be 

 found. However, if Marckwald had heated the originally ob- 

 tained mixture of the brucine-ssdts immediately, and in such a 



1) M. Scholtz, Ber. d. d. Chem. Ges. 34. 3015. (1901). 



2) W. Marckwald, Ber. d. d. Chem. Ges. 37. 349. (1904). 



3) S. Tymstra Bzn, Ber. d. d. Chem. Ges. 38. 2165. (1905). 



4) J. B. Cohen and T. S. Patterson, Ber. d. d. Chem. Ges. 37. 1012. (1904) ; 

 W. Marckwald, ibid. 37. 1368. (1904). 



