4,6-O-苄叉缩醛缩醛水解反应的加速和减速因素。,The Journal of Organic Chemistry

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4,6-O-苄叉缩醛缩醛水解反应的加速和减速因素。
The Journal of Organic Chemistry ( IF 3.3 ) Pub Date : 2020-04-28 , DOI: 10.1021/acs.joc.0c00395
Yuta Maki _{1,

2} , Kota Nomura _{1,

2} , Ryo Okamoto _{1,

2} , Masayuki Izumi ₁ , Yasuhisa Mizutani ₁ , Yasuhiro Kajihara _{1,

2}

Affiliation

亚苄基乙缩醛基不仅在碳水化合物化学中而且在一般有机化学中都是最重要的保护基团之一。在4，6- O-亚苄基糖苷的情况下，我们先前发现4-位的立体化学改变了亚苄基缩醛基水解的反应速率常数。但是，尚不清楚加减速因子的细节。在这项工作中，使用Arrhenius和Eyring图分析了亚苄基乙缩醛基团的水解反应，以获得葡萄糖苷（Glc），甘露糖苷（Man）和半乳糖苷（Gal）的各个参数。阿列纽斯和情节的Eyring表明预指数因子（甲）和Δ小号^⧧对于非乙酰化底物中Gal的最小反应速率常数至关重要。在另一方面，这两种Ë_一个/Δ ħ ^⧧和阿/Δ小号^⧧是显要为二乙酰基板间加的最小反应速率常数。获得的所有参数表明，水解反应的速率常数通过质子化和水合步骤以及溶剂化来调节。所获得的参数支持广泛使用亚苄基缩醛基团的作为正交保护的顺式-和反式通过的快速水解-融合的双环系统的反式-融合亚苄基缩醛基团。

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Acceleration and Deceleration Factors on the Hydrolysis Reaction of 4,6-O-Benzylidene Acetal Group.

The benzylidene acetal group is one of the most important protecting groups not only in carbohydrate chemistry but also in general organic chemistry. In the case of 4,6-O-benzylidene glycosides, we previously found that the stereochemistry at 4-position altered the reaction rate constant for hydrolysis of benzylidene acetal group. However, a detail of the acceleration or deceleration factor was still unclear. In this work, the hydrolysis reaction of benzylidene acetal group was analyzed using the Arrhenius and Eyring plot to obtain individual parameters for glucosides (Glc), mannosides (Man), and galactosides (Gal). The Arrhenius and Eyring plot indicated that the pre-exponential factor (A) and ΔS^⧧ were critical for the smallest reaction rate constant of Gal among nonacetylated substrates. On the other hand, both E_a/ΔH^⧧ and A/ΔS^⧧ were influential for the smallest reaction rate constant of Gal among diacetylated substrates. All parameters obtained suggested that the rate constant for hydrolysis reaction was regulated by protonation and hydration steps along with solvation. The obtained parameters support wide use of benzylidene acetal group as orthogonal protection of cis- and trans-fused bicyclic systems through the fast hydrolysis of the trans-fused benzylidene acetal group.

更新日期：2020-04-28

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