204 A GENERAL REVIEW OF 



was found to be identical with the pentamethyl salicin obtained 

 by direct alkylation of the glucoside. Thus salicin, like 

 methylglucoside, possesses the y-oxidic linkage as do also the 

 related glucosides helicin and populin, which can be obtained 

 from salicin by reactions which do not interfere with the gluco- 

 sidic linkage. 



The alkylation process has also been applied by Moore 

 and Tutin (55) to the natural glucoside gynocardin, or rather 

 to the gynocardinic acid derived from it by the action of 

 barium hydroxide and subsequent decomposition of the 

 barium salt by sulphuric acid. The acid was methylated in 

 the usual manner, first in methyl alcohol and afterwards in 

 methyl iodide solution, and yielded methyl pentamethyl- 

 gynocardinate ; the two remaining hydroxyl groups resisted 

 the action of the alkylating agents, and are therefore probably 

 phenolic. The substance, like pentamethyl salicin, gave resin- 

 ous products on hydrolysis by dilute acids, and no attempt 

 was made to overcome this difficulty or to isolate the methy- 

 lated sugar. 



The hexoses readily form condensation compounds with 

 acetone. The monoacetone derivatives are glucosidic, and, in 

 their formation, one molecule of sugar unites with a molecule 

 of acetone with the elimination of a molecule of water. 

 Methylation of these compounds by means of the silver oxide 

 reaction affords an insight into their structure. Acetone- 

 rhamnoside treated in this way yields a dimethylated deriva- 

 tive, and hence the formula suggested by Fischer for the 

 parent compound, 



Me . CH(OH) . CH . (CHOH) 2 . CH . . CMe : CH e , 

 I o_ 



is excluded, since it contains three secondary hydroxyl groups. 

 Dimethyl acetonerhamnoside is readily hydrolysed, yielding 



