198 A GENERAL REVIEW OF 



Mention should be made of the preparation of a number 

 of alkylated glucose derivatives which have been prepared 

 with the object of determining the constitution of the parent 

 glucose compounds ; these are referred to in a later section. 



The methods which have been applied to the preparation 

 of alkylated derivatives of glucose serve also for the production 

 of similar compounds of other sugars. a-Methylgalactoside, 

 when fully methylated, gives a colourless, liquid tetramethyl 

 a-methylgalactoside, and on hydrolysis with dilute hydro- 

 chloric acid, the latter compound yields the corresponding 

 sugar, tetramethyl galactose (Irvine and Cameron (26) ). 

 This substance differs from tetramethyl glucose in being an 

 uncrystallisable syrup, and experiments on the mutarotation 

 of the compound are therefore restricted, but not so far as to 

 conceal the analogy between the two alkylated sugars. Further 

 alkylation of tetramethyl galactose results in the production 

 of a mixture of the stereoisomeric tetramethyl a- and /3-methyl- 

 galactosides in which the /3-isomeride is in large excess. The 

 analogy is further exemplified by the fact that tetramethyl 

 /3-methylgalactoside is, like the corresponding glucoside, a 

 crystalline compound. Again, by processes similar to those 

 already described, Irvine and Moodie (31) from a-methyl- 

 mannoside, have prepared tetramethyl a- and /3-methyl- 

 mannosides and tetramethyl mannose. In this case the 

 methylated a-mannoside is a crystalline solid, the isomeric 

 ^8-mannoside a liquid, and the mannose a colourless syrup. 

 With respect to their optical activity and other attributes, 

 the compounds fall into line with the corresponding glucose 

 and galactose derivatives. 



The aldo-pentoses and methylpentoses behave like the 

 aldo-hexoses mentioned, in that they yield alkylated deriva- 

 tives when their methylglucosides are subjected to the 

 alkylation process. Purdie and Rose (35), starting with 

 a-methylarabinoside, obtained trimethyl a-methylarabinoside, 

 a compound which forms extraordinarily large and beautiful 



