DISACCHARIDES 121 



may be used to distinguish between these varieties of Sac- 

 charomyces. The constitution * of meHbiose is represented by 

 the formula — 



CHOH . (CHOH)3 . CH— CHj— O— CII . (CHOH)3 . CH . CH^OH 



! o ■ ' o 



Glucose Galactose 



DISACCHARIDES PRODUCED BY THE UNION OF 

 A HEXOSE WITH A PENTOSE. 



Several disaccharides have been discovered which on 

 hydrolysis yield one molecule each of a hexose and a pentose ; 

 some of the more important of these are the following : — 



PRIMEVEROSE. C^^H^^Oi^. 



Primeverose is prepared from the glucosides primeverin and 

 primulaverin occurring in Primula officinalis.'f This sugar 

 has ai)— 379° and melts at 210°. It has a free aldehyde 

 group and would therefore appear to have the constitution — 



CHO . [CH0H]4 . CH, . O . CH . CH . [CHOH], . CH„OH 



O 



This disaccharide has also been found to occur in the 

 glucosides gentiacaulin and monotropitin, the latter of which 

 occurs in Monotropa hypopitys, in the bark of Betula lenta, 

 and in the fresh roots of Spircea Ulmaria, S. Filipendula, and 

 S. gigantea. 



The fact that this carbohydrate has thus been found to 

 occur in five families, namely, Betulaceae, Monotropeae, 

 Primulaceae, Gentianaceae, and Rosacese, would indicate that 

 it has a much wider distribution than was formerly suspected.^ 



VICIANOSE. C11H20O10. 



This disaccharide is obtained by the hydrolysis of the 

 glucoside vicianin occurring in Vicia angustifolia, and gein 



* Charlton, Haworth, and Hickinbottom : " J. Chem. Soc," 1927, 1527. 

 Haworth, Leach, and Long : id., 1927, 3146. 



t Goris and Vischniac : " Compt. rend.," 1919, 169. 871, 975. 

 I Bridel : id., 1924, 179, 991. 



