Of gentiobiose

Some of the original work in the carbohydrate area in particular reveals extensive protection of carbonyl and hydroxyl groups. For example, a cyclic diacetonide of glucose was selectively cleaved to the monoacetonide. A summary describes the selective protection of primary and secondary hydroxyl groups in a synthesis of gentiobiose, carried out in the 1870s, as triphenylmethyl ethers. 

The naturally-occurring 1,6-linked glucose polymers furnish other sources of 2,3,4-trimethyl-D-glucose, which has been isolated from the hydrolysis products of the methyl ethers of gentiobiose,112 118 melibiose,114 raffmose106 116 and dextran.78 74,116... 

Figure 2. Schematic diagram of the hydrogen-bond structure in the crystal structure of gentiobiose (GENTOSOl REFCODE in Cambridge Crystallographic Data Base). The arrows indicate infinite chains. Distances are H—O in A, angles are 0-H—O in degrees. The covalent 0-H bond lengths have been normalized to 0.97 A.

From a similar comparison with non-optimized functions, PEF300 (8) without and PEF400 (10) with charges, we see that the conformational details are not nearly so well reproduced. In the case of gentiobiose the optimized PEF has therefore made a real improvement. 

In the preparation of gentiobiose octaacetate (Helferich and Leete ), 15 g. of emulsin and 20 ml. of toluene was added to a solution of glucose in distilled water, the mixture was let stand in a glass-stoppered flask for 5 weeks with occasional CHjOH... 

---