204 Biological Chemistry. 



acid a cyanhydrin is produced, which on oxidation yields the 

 corresponding acid, and the lactone of this acid on reduction 

 yields a sugar 

 CHO ON COOH CHO 



(CH(OH)) 8 ^ CH(OH) " CH(OH) CH(OH) 



CH 2 (OH) t HCN] (CH(OH)) 3 [ \ys]~ (CH(OH)) 3 [ration] (CH(OH)),, 



CH 2 (OH) CH 2 (OH) CH 2 (OH) 



This reaction introduces a new asymmetric carbon atom, 

 and a mixture of sugars is generally produced, the steric 

 relationship to one another of which may be represented 

 by the formulae 



CHO CHO 



(OH)CH HC(OH) 



and 

 fC3 



(CH(OH)) 3 (CH(OH)) 3 



CH 2 (OH) CH 2 (OH) 



The relative position of the hydrogen atoms and hydroxy 

 groups on the other three carbon atoms will be the same 

 in the pentoses and hexoses. 



IV. It is possible to pass from a higher to a lower 

 monosaccharose. There are various methods for accom- 

 plishing this purpose, the simplest being that due to Kuff < 

 The sugar is first oxidized to a monobasic acid, and the| 

 latter on oxidation with hydrogen peroxide in the presence 

 of an iron salt (Fenton's reagent) is oxidized to a sugar 

 containing one carbon atom less. In this way the pentose. 

 arabinose, has been produced from glucose. The arrange- 

 ment of the hydrogen atoms and hydroxyl groups attached 

 to the three asymmetric carbon atoms, in arabinose, must 

 therefore be the same as those attached to three of thd 

 asymmetric carbon atoms of glucose. The reactions may 

 be represented by the following formulae : 



