166 PREPARATION OF METHYLATED SUGARS 



3:5:6 TEIMETHYL GLUCOSE 

 CH 2 (OCH 3 ) . CH(OCH 3 ) . CH . CH(OCH 3 ) . CH(OH) . CH(OH) 







In the preparation of the above compound glucosemono- 

 acetone was alkylated, first in acetone solution and afterwards 

 in methyl iodide solution. The liquid product, isolated from 

 the reaction, boiled at 138-139/12 mm. and had apparently 

 undergone partial hydrolysis as it possessed a decided action 

 upon Fehling's solution, and gave, on analysis, figures inter- 

 mediate between those required for trimethyl glucosemono- 

 acetone and trimethyl glucose. This result is not surprising 

 considering the ease with which glucosemonoacetone is 

 hydrolysed. The optical values observed for the methylated 

 acetone compound have in consequence little significance, but 

 the fact that the compound is laevo-rotatory ([a]f 27'2 in 

 methyl alcohol) is nevertheless remarkable. 



The hydrolysis was carried out exactly as in the prepara- 

 tion of monomethyl glucose, but as the sugar could not be 

 obtained in the crystalline state the syrup examined would 

 consist of the equilibrium mixture of a- and /3-forms. The 

 proportion of the latter variety was therefore increased by 

 heating the compound at 70 for half an hour, and, on solution 

 in alcohol, the following optical values were obtained : 



Initial Specific Rotation. Permanent Specific Rotation. 



-6-2 > 8-3 



As already indicated, the rotatory power of this sugar is in 

 every respect abnormal. Whereas both the a- and /3-forms of 

 glucose, and also of all the other known methylated glucoses, 

 are dextrorotatory, the equilibrium value for 3:5:6: tri- 

 methyl glucose is laevo. Not only so, but the mutarotation 

 recorded above indicates that the /3-form is either dextro- or 

 feebly laevo-rotatory, as the change ft > a results in an increase 



