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首页> 外文期刊>Journal of Wood Chemistry and Technology >ABSOLUTE CONFIGURATION OF beta- AND alpha-ASYMMETRIC CARBONS WITHIN beta-O-4-STRUCTURES IN HARDWOOD LIGNIN
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ABSOLUTE CONFIGURATION OF beta- AND alpha-ASYMMETRIC CARBONS WITHIN beta-O-4-STRUCTURES IN HARDWOOD LIGNIN

机译：硬木木质素中具有β-O-4-结构的β-和α-不对称碳的绝对构型

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摘要

In this study, we investigated the proportion of erythro-and threo-forms of beta-O-4-ether structures and their enantiomeric compositions in hardwood lignin by applying the ozonation method to birch wood meal. Optical activity was not substantially observed in either the erythronic or threonic acids obtained as the ozonation products of beta-O-4-structures in birch wood meal. The proportions of the four stereoisomeric forms {(alpha S,beta R)-erythro, (alpha R,beta R)-threo, (alpha S,beta S)-threo, and (alpha R,beta S)-erythro forms} were estimated to be 37-38%, 13-14%, 12-13%, and 36-37% based on the yields of erythronic and threonic acids, and on their optical activities. The proportions suggest that the entire components of beta-O-4-ether structures in birch wood lignin have R-and S-configurations at the beta-carbon in approximately the same quantities {(beta R)-beta-O-4-structure: (beta S)-beta-O-4structure = 50-52: 48-50}; i.e., that the beta-ether structures are essentially racemic. This estimation implies that, during lignin biosynthesis, an equal number of enantiomeric forms of beta-O-4-bonded quinone methides were formed by radical coupling reactions.
机译：在这项研究中，我们通过将臭氧化方法应用于桦木粉中，研究了硬木木质素中β-O-4-醚结构的赤型和苏型形式的比例及其对映体组成。在桦木粉中作为β-O-4-结构的臭氧化产物而获得的赤藓酸或苏糖酸中均未观察到光学活性。四种立体异构体形式的比例（{αS，βR）-赤型，（αR，βR）-苏型，（αS，βS）-苏型和（αR，βS）-赤型}基于赤藓酸和苏糖酸的收率及其光学活性，估计为37-38％，13-14％，12-13％和36-37％。比例表明，桦木木质素中β-O-4-醚结构的全部成分在β-碳上具有大致相同的{-β-R-4-β-O-4-结构：（βS）-β-O-4结构= 50-52：48-50}；即，β-醚结构本质上是外消旋的。该估计表明，在木质素生物合成过程中，通过自由基偶联反应形成了相等数量的β-O-4-键合醌甲基化物的对映体形式。

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