To structurally characterize periodate-oxidized cellulosic substrates, methyl 4-O-methyl β-d-glucopyranoside and methyl 4’-O-methyl-cellobioside were subjected to periodate treatment at pH 4.8–5.0. Oxidation of the monosaccharide using two molar equivalents of oxidant produced 3-methoxy-2,5-dihydro-2-furanol as main product. To confirm its structure and mode of formation, 6-O-bisdeuteromethyl 4-O-methyl-β-d-glucopyranoside and methyl 4-O-trisdeuteromethyl-β-d-glucopyranoside were synthesized and oxidized to generate 3-methoxy-5-deutero-2-hydro-2-furanol in the former case and 3-trisdeuteromethoxy-2,5-dihydro-2-furanol in the latter case. Oxidation using one molar equivalent of periodate led to preferential formation of hemialdal products and (E)-4-hydroxy-2-methoxy-2-butenal. The latter product was also formed upon end-wise oxidation of methyl 4’-O-methyl-cellobioside, wherein the reducing unit was released as non-oxidized methyl β-d-glucopyranoside. This data indicate that periodate oxidation of cellulosic model substrates might be accompanied by peeling reactions and formation of β-elimination products even under slightly acidic conditions.

Graphical abstract

中文翻译：

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β-消除是纤维素模型单糖和二糖高碘酸盐氧化中的主要副反应

为了表征高碘酸盐氧化的纤维素底物的结构，在 pH 4.8–5.0 下对甲基 4- O-甲基 β- d-吡喃葡萄糖苷和甲基 4'- O-甲基-纤维二糖苷进行高碘酸盐处理。使用两摩尔当量的氧化剂氧化单糖产生3-甲氧基-2,5-二氢-2-呋喃醇作为主要产物。为了确认其结构和形成模式，合成了6- O-双氘代甲基4 -O-甲基-β -d-吡喃葡萄糖苷和甲基4 -O-三氘代甲基-β- d-吡喃葡萄糖苷，并氧化生成3-甲氧基-5-前一种情况为氘代-2-氢-2-呋喃醇，后一种情况为3-三氘甲氧基-2,5-二氢-2-呋喃醇。使用一摩尔当量的高碘酸盐进行氧化导致优先形成半缩醛产物和( E )-4-羟基-2-甲氧基-2-丁烯醛。后一产物也是在甲基4'- O-甲基-纤维二糖苷的末端氧化时形成的，其中还原单元作为未氧化的甲基β- d-吡喃葡萄糖苷释放。该数据表明，即使在微酸性条件下，纤维素模型底物的高碘酸盐氧化也可能伴随剥离反应和β-消除产物的形成。

图形概要