Maltoside -6 -trityl

The two primary hydroxyl groups in maltose and its derivatives show a large difference in reactivity. On selective tritylation, /3-maltose,238 benzyl /3-maltoside,239 and methyl 3-0-(methylsulfonyl)-/3-maltoside127 all gave mainly 6 -0-trityl compounds. Tritylation of cyclohexaamylose130 and amylose132,240 yielded the expected 6-0-trityl derivatives. 

Attempts66 to prepare the 2,3-anhydride from methyl 3-0-(methyl-sulfonyl)-/3-maltoside, using M sodium methoxide, resulted in the corresponding 3,6-anhydride 43. To circumvent the formation of 43, the reaction was performed with methyl 3-0-(methylsulfonyl)-6,6 -di-0-trityl-/3-maltoside. The desired product, methyl 2,3-anhydro-4-0-(2,3,4-tri-0-acetyl-6-0-trityl-a-D-glucopyranosyl)-6-0-trityl-/3-D-allopyrano-side (44), was obtained in 72% yield. Attempted detritylation of 44 by brief treatment with hydrogen bromide in glacial acetic acid, followed by conventional acetylation, gave methyl 2,6,2, 3, 4, 6 -hexa-0-acetyl-... 

Ethyl 1-thio /J-maltoside 6 -0-trityl-hexa-O-acetyl- 101-103 + 71 C 44... 

The observed differences [3] in the reactivity of primary hydroxyl groups were preparatively exploited in the structural modifications of oligosaccharides. The monomolar tritylation of phenyl a-maltoside gives the 6 - to 6- ratio of about 1.3, whereas 2.9 is observed for phenyl P-maltoside [269]. Generally, the orientation of... 

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