AND POLYHYDRIC ALCOHOLS 175 



mannitol, although unconnected with an asymmetric carbon 

 atom, assume preferentially different positions which affect 

 the stability of the condensation derivatives. According to 

 this view, mannitol triacetone exists in only one form, the 

 linkage of the ketonic residues being trans, trans, cis. 



APPLICATIONS OF PARTIALLY METHYLATED POLYHYDRIC 



ALCOHOLS 



The most important application of these compounds will 

 doubtless be found in the opportunity they afford for con- 

 firming configuration. From their mode of formation, the 

 compounds contain hydroxyl and methoxyl groups, the 

 position of the former alone being favourable to condensation 

 with acetone. In other words, these groups represent cis and 

 trans positions respectively in the original compound so that 

 determination, by standard methods, of the distribution of the 

 alkyloxy groups gives the configuration. 



Another possible development of this line of research is the 

 preparation of methylated aldoses, isomeric with alkylated 

 sugars prepared from glucosides, but containing the methoxyl 

 group in the y-position and thus capable of functioning as 

 aldehydes only. The examination of compounds of this class, 

 with respect to their capacity to display mutarotation and to 

 participate in glucoside formation, should afford definite 

 evidence as to the structural causes of these phenomena in the 

 reducing sugars. 



Again, as in the case of partially methylated sugars, the 

 behaviour of the corresponding alcohols towards catalytic 

 fermenting agents should be capable of yielding results bear- 

 ing directly on the mechanism of these changes. 



Finally, the compounds are readily converted into mixed 



