Sucrose selective tritylation

Acetates. Because of the significant interest in selective acetylation reactions of sucrose, the need for a convenient and unambiguous method of identification has been recognized (34,35). The position of an acetyl group in a partially acetylated sucrose derivative can be ascertained by comparison of its H-nmr acetyl methyl proton resonances after per-deuterioacetylation with those of the assigned octaacetate spectmm. The synthesis of partially acetylated sucroses has generally been achieved either by way of selectively protected derivatives such as trityl ethers and cychc acetals or by direct selective acetylation and deacetylation reactions. 

The ready condensation of sucrose with excess triphenylmethyl chloride in pyridine to a tri-trityl ether is, however, more easily explained by XV or II, which have three, instead of two (c/. I), primary alcohol groups to react selectively in the condensation. Fleury and Courtois oxidized sucrose for twenty-four hours at 14° with an excess of suitably buffered periodic acid and found that three moles of the oxidant were consumed and one mole of formic acid was eliminated. This highly selective oxidant is known to cleave unsubstituted 1,2 glycols quantitatively to two carbonyl groups and to eliminate the center carbon atom... 

The tosylation of cellobiose by tosyl chloride in pyridine and thermal analysis gf the products using DTA and isothermal TGA has been carried out. Selective tosylation of 6,1, 6 -tri-O-trityl sucrose gave the 2-tosylate and not the 3-toaylate as previously claimed by I.Jeze ( Chem. Zvesti. 1971, 25, 369). Base treatment of this gave 40% 2,3-manno-epoxide (54), which was opened with a variety of nucleophiles in all cases the 3-nucleophilo-altro product resulted (Scheme 9). With ammonium thiocyanate, the acetyl-ated epoxide (55) gave the 2.3-allo-epithio disaccharide (56). Imidazolylsulphonyl derivatives of carbohydrates and their reactions are mentioned in Chapter 10. 

Another scheme for selectively modifying the C-6 hydroxyl group of sucrose involves the removal of the benzilidene group from 2,3,l, 3, 4, 6 -hexa-0-benzoyl-4,6-0-benzilidene sucrose by refluxing with iodine in methanol [25]. The resulting hexa-(9-benzoyl sucrose can be tritylated at C-6 and benzoylated at... 

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