On the Structure of the so Called 5-methyl Glucose of Ohle and Von Vargha

In continuation of the work on the nature of the glycoside formation in the partially substituted sugars,’ a study of the 5methyl glucose described by Ohle and von Vargha2 was undertaken by us. On the basis of previous experience, a substance of this structure was expected to form but one glucoside, the furanoside, and it was therefore surprising to find indication of the formation of two glucosides. These were formed, moreover, at approximately the same rates as in the case of unsubstituted glucose. The formation of two glucosides from 5-methyl glucose would require either the existence of glucosides with ring structures other than < 1, 4> and < 1, 5 >, or else the migration of the methyl group in the course of glucoside formation. Further study, however, has convinced us that no irregularity had occurred but that instead an incorrect structure has been assigned by Ohle to his substance, which in reality is 6-methyl glucose. The following observations led to this conclusion. The osazone of the substance described by Ohle has a melting point (180-185”) which is very close to that last reported for 6-methyl glucosazone (184-187” corrected).3 The rotation of the osazone of the “5methyl” glucose was reported as 101.9” in pyridine,2 and this we have confirmed. However, in alcohol the “5-methyl” glucosazone has initial and final rotations of -70” and -44’ respectively. These values are practically identical with those reported by