AND POLYHYDRIC ALCOHOLS 161 



in the preparation of the corresponding glucose compound, 

 and thus included the intermediate formation of monomethyl 

 fructosediacetone. This compound crystallises in square 

 plates melting at 115, showed [a] D 136*4 in methyl alcoholic 

 solution, and was hydrolysed by heating with 0*1 per cent, 

 hydrogen chloride. The rotatory changes then observed 

 indicate that the two acetone residues are removed in suc- 

 cessive stages, an observation which is of importance in 

 establishing the constitution of the compound. The subse- 

 quent isolation of the free sugar was carried out in the usual 

 manner and yielded monomethyl fructose as a readily crystal- 

 lisable sugar melting at 122-123 and showing all the properties 

 of a reducing ketose. 



The following observations of mutarotation were made : 



Solvent. Initial [a] D Permanent Initial [a] D 



of a-form. [a] D . after fusion. 



Water . . . -70- 5 > -53' 1 -41'9 



Methyl Alcohol -74-1 --> -22'1 ^- 12-5 



The constitution of the sugar, deduced from its behaviour 

 towards phenyl hydrazine, oxidising agents, and in condensa- 

 tion reactions, is represented by the structure : 



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

 



DIMETHYLATED REDUCING SUGARS 

 DIMETHYL GLUCOSE 



For the preparation of this compound two of the hydroxyl 

 groups in glucose, in addition to the reducing group, must 

 be protected from methylation by the introduction of hydro- 

 lysable residues, and we thus made use of the benzylidene 

 a-methylglucoside described by Van Eckenstein. 



