SYNTHETIC WORK IN CARBOHYDRATES 335 



From all sources the number of simple sugars, from the be- 

 ginning of the century to less than ten years ago, numbered 

 not over 6. Now, by means of synthetical research, not less 

 than 30 simple sugars are known, and 7 of them are natural 

 products. Among the 7 carbon-atom sugars, by calculating 

 the possible number of isomers, 32 are possible, of which only 

 6 have thus far been obtained. Of the 128 possible nonose 

 sugars, as yet but 2 have been made. 1 



To carry out the thought of the sugar-group development 

 it will be necessary to give rapidly an outline of these sugars 

 before summing up the methods which led to their synthesis. 



Under the mannite group are included grape sugar and 

 sugars possessing the same chemical composition as grape 

 sugar. The mannose sugars also come under this group, with 

 their corresponding alcohols and acids. The right, left, and 

 inactive mannose correspond to the d-l and i glucose. The 

 right mannose is formed at the same time as the right fructose, 

 by the careful oxidation of the alcohol mannite. It was first 

 obtained in this way. It may be mentioned that mannite is 

 found in manna. Mannose may also be obtained from the 

 natural carbohydrates by hydrolytic reaction. It is also found 

 in the fruit of many palms. A very cheap source of supply is 

 from the shavings of vegetable ivory in the manufacture of 

 buttons. In separating the right mannose from its solutions, 

 its phenylhydrazone compound is used. This compound is 

 very insoluble, and affords a characteristic test for this sub- 

 stance. 



The left mannose is obtained from the left arabinose. 2 The 

 arabinose compounds contain 5 atoms of carbon. The cyan- 

 hydrine reaction in the sugar series, or Kiliani's reaction, is 

 the one employed in its formation. This method has opened 

 the field to some of the most important discoveries in sugar 

 synthesis. In this reaction prussic acid unites directly with 

 sugar, 3 and in this way the number of carbon atoms in the 



1 The table shows the present sugar status. 



2 By right, left, and inactive acids, of course, is meant the effect of these 

 compounds on polarized light. 



3 C 2 HOH(CHOH) t CHO + HCN=CH 2 OH(CHOH) 4 CHOH . CN+H 2 O. 



