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首页> 外文期刊>Carbohydrate research >Complications of modeling glycosylation reactions: Can the anomeric conformation of a donor determine the glycopyranosyl oxacarbenium ring conformation?
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Complications of modeling glycosylation reactions: Can the anomeric conformation of a donor determine the glycopyranosyl oxacarbenium ring conformation?

机译:模拟糖基化反应的复杂性:供体的端基异构构象能否确定糖吡喃糖基氧杂碳鎓环构象?

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摘要

That the ring conformation of glycopyranosyl oxacarbenium ions can influence the stereochemical outcome of glycosylation reactions has been postulated for some time. Some new ionization calculations show that the ultimate conformation ~4H _3 or ~5S _1 of d-glucopyranosyl oxacarbenium ions depends on the initial ~(φH) (CH-1-C-1-S ~+-SCH _3) conformation of anomeric thiosulfonium ions. Evidence is also presented that nucleophile:electrophile hydrogen bonded complexes, 1,6-anhydro-carbenium ions and electron rich carbon nucleophile:oxacarbenium ion complexes are all probably artifacts of neglecting counter ions or nucleophiles in the DFT calculation. All three cationic species are likely important for glycosylation reaction side reactions but not as productive species.
机译:糖基吡喃糖基氧杂碳鎓离子的环构象会影响糖基化反应的立体化学结果已经有一段时间了。一些新的电离计算表明,d-吡喃葡萄糖基氧杂碳鎓离子的最终构象〜4H _3或〜5S _1取决于异头硫磺the的初始〜(φH)(CH-1-C-1-S〜+ -SCH _3)构象。离子。也有证据表明亲核试剂:亲电子氢键络合物,1,6-脱水碳鎓离子和富电子碳亲核试剂:氧碳鎓离子络合物都可能是DFT计算中忽略反离子或亲核试剂的产物。所有这三种阳离子物质可能对糖基化反应副反应都很重要,但不是生产性物质。

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