In situ Switching of Site-Selectivity with Light in the Acetylation of Sugars with Azo-Peptide Catalysts.
In situ Switching of Site-Selectivity with Light in the Acetylation of Sugars with Azo-Peptide Catalysts.
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DOI：
10.1021/acs.joc.9b01913
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发表时间：
2019-11
期刊：
影响因子：
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通讯作者：
Dominik Niedek;Frederik R. Erb;C. Topp;Alexander Seitz;R. Wende;A. Eckhardt;J. Kind;D. Herold;C. Thiele;P. Schreiner
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文献类型：
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作者：
Dominik Niedek;Frederik R. Erb;C. Topp;Alexander Seitz;R. Wende;A. Eckhardt;J. Kind;D. Herold;C. Thiele;P. Schreiner
我们提出了一种新概念，使用配备偶氮苯部分的寡肽催化剂，基于光作为外部刺激，对部分受保护的糖的催化乙酰化的位点选择性进行原位控制。可异构化的偶氮苯肽主链决定了催化袋的大小和形状，而 π-甲基-L-组氨酸 (Pmh) 部分则转移亲电子试剂。使用 LED (λ = 365 nm) 将 E- 光异构化为 Z-偶氮苯催化剂（通过 NMR 监测）极大地改变了催化活性 Pmh 部分周围的化学环境，从而使光诱导的催化剂形状变化改变了位点选择性。作为原理验证，我们采用了 (4,6-O-亚苯亚甲基)甲基-α-D-吡喃糖苷，它在室温下将单乙酰化产物的区域选择性从 2:1 (E) 更改为 1:5 (Z)。天然产物槲皮素的区域选择性乙酰化进一步证明了这种新催化剂设计概念的有效性。原位辐照核磁共振光谱用于量化紫外光连续辐照下的光稳态。
We present a novel concept for the in situ control of site-selectivity of catalytic acetylations of partially protected sugars based on light as external stimulus using oligopeptide catalysts equipped with an azobenzene moiety. The isomerizable azobenzene-peptide backbone defines the size and shape of the catalytic pocket while the π-methyl-L-histidine (Pmh) moiety transfers the electrophile. Photoisomerization of the E- to the Z-azobenzene catalyst (monitored via NMR) with an LED (λ = 365 nm) drastically changes the chemical environment around the catalytically active Pmh moiety so that the light-induced change in catalyst shape alters site-selectivity. As a proof-of-principle we employed (4,6-O-benzylidene)methyl-α-D-pyranosides, which provide a change in regioselectivity from 2:1 (E) to 1:5 (Z) for the monoacetylated products at room temperature. The validity of this new catalyst-design concept is further demonstrated with the regioselective acetylation of the natural product quercetin. In situ irradiation NMR spectroscopy was used to quantify photostationary states under continuous irradiation with UV light.