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Mechanistic Insights into the Conversion of Biorenewable Levoglucosanol to Dideoxysugars
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2020-10-22 , DOI: 10.1021/acssuschemeng.0c06315 Mingxia Zhou 1 , Siddarth H. Krishna 2 , Mario De bruyn 3 , Bert M. Weckhuysen 3 , Larry A. Curtiss 1 , James A. Dumesic 2 , George W. Huber 2 , Rajeev S. Assary 1
ACS Sustainable Chemistry & Engineering ( IF 7.1 ) Pub Date : 2020-10-22 , DOI: 10.1021/acssuschemeng.0c06315 Mingxia Zhou 1 , Siddarth H. Krishna 2 , Mario De bruyn 3 , Bert M. Weckhuysen 3 , Larry A. Curtiss 1 , James A. Dumesic 2 , George W. Huber 2 , Rajeev S. Assary 1
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A molecular understanding of the conversion of biorenewable threo- and erythro-levoglucosanol (LGOL) to 3,4-dideoxysugars in aqueous medium is provided based on first-principles simulations. The synthetic importance of this transformation is that these intermediates can be quantitatively hydrogenated to (S,S)/(S,R) hexane-1,2,5,6-tetrol (tetrol), whose stereochemistry depends on which dideoxy sugar intermediates are formed during LGOL conversion. The thermodynamic and kinetic feasibility of the acetal (R2C(OR)2) hydrolysis in LGOL is investigated via computing the free energy profile. In aqueous medium, the rate-determining step of LGOL hydrolysis is the protonation of the anhydro-bridge oxygen atom of LGOL concurrent with ring opening, yielding the cyclic forms of 3,4-dideoxymannose (DDM) and 3,4-dideoxyglucose (DDG) from threo- and erythro-LGOL, respectively. The measured activation energies of LGOL hydrolysis are 20.5 and 23.6 kcal/mol for DDM and DDG formation, respectively. These values are in agreement with the computed protonation free energies of 17.1 and 18.2 kcal/mol, respectively. Based on the simulations, a Brønsted base-catalyzed isomerization from DDG or DDM to 3,4-dideoxy fructose (DDF) is preferred with lower apparent activation free energy barriers compared to the acid-catalyzed isomerization. In summary, this study provides mechanistic information about the conversion of the biomass-derived anhydro-sugar LGOL to 3,4-dideoxy sugars, which are precursors to renewable high-value chemicals.
中文翻译：
机械可察觉的生物可再生的左旋葡萄糖醇转化为双脱氧糖的见解。
基于第一性原理模拟，提供了分子生物学对水性介质中生物可再生苏糖和赤藓糖基葡萄糖醇（LGOL）转化为3,4-二脱氧糖的认识。此转化的合成重要性在于，这些中间体可以定量加氢为（S，S）/（S，R）己烷-1,2,5,6-tetrol（tetrol），其立体化学取决于哪些双脱氧糖中间体是在LGOL转换过程中形成的。缩醛（R 2 C（OR）2）在LGOL中水解的热力学和动力学可行性通过计算自由能分布。在水性介质中，LGOL水解的决定速度的步骤是LGOL的脱水桥氧原子的质子化与开环同时产生3,4-二脱氧甘露糖（DDM）和3,4-二脱氧葡萄糖（DDG）的环状形式）（来自Threo-和erythro）-LGOL，分别。对于DDM和DDG形成，测得的LGOL水解的活化能分别为20.5和23.6kcal / mol。这些值分别与计算的质子化自由能17.1和18.2kcal / mol一致。基于模拟，与酸催化的异构化相比，从DDG或DDM到3,4-二脱氧果糖（DDF）的布朗斯台德碱催化异构化具有较低的表观活化能垒是优选的。总而言之，这项研究提供了有关将生物质衍生的脱水糖LGOL转化为3,4-二脱氧糖（可再生高价值化学品的前身）的机制信息。
更新日期：2020-11-02
中文翻译：
机械可察觉的生物可再生的左旋葡萄糖醇转化为双脱氧糖的见解。
基于第一性原理模拟，提供了分子生物学对水性介质中生物可再生苏糖和赤藓糖基葡萄糖醇（LGOL）转化为3,4-二脱氧糖的认识。此转化的合成重要性在于，这些中间体可以定量加氢为（S，S）/（S，R）己烷-1,2,5,6-tetrol（tetrol），其立体化学取决于哪些双脱氧糖中间体是在LGOL转换过程中形成的。缩醛（R 2 C（OR）2）在LGOL中水解的热力学和动力学可行性通过计算自由能分布。在水性介质中，LGOL水解的决定速度的步骤是LGOL的脱水桥氧原子的质子化与开环同时产生3,4-二脱氧甘露糖（DDM）和3,4-二脱氧葡萄糖（DDG）的环状形式）（来自Threo-和erythro）-LGOL，分别。对于DDM和DDG形成，测得的LGOL水解的活化能分别为20.5和23.6kcal / mol。这些值分别与计算的质子化自由能17.1和18.2kcal / mol一致。基于模拟，与酸催化的异构化相比，从DDG或DDM到3,4-二脱氧果糖（DDF）的布朗斯台德碱催化异构化具有较低的表观活化能垒是优选的。总而言之，这项研究提供了有关将生物质衍生的脱水糖LGOL转化为3,4-二脱氧糖（可再生高价值化学品的前身）的机制信息。
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