Regioselective benzoylation of unprotected β-glycopyranosides with benzoyl cyanide and an amine catalyst - application to saponin synthesis
Regioselective benzoylation of unprotected β-glycopyranosides with benzoyl cyanide and an amine catalyst - application to saponin synthesis
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DOI：
10.1039/d0qo01243b
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发表时间：
2021-01-21
影响因子：
5.4
通讯作者：
Peng, Peng
中科院分区：
文献类型：
--
作者：
Li, Tianlu;Li, Tong;Peng, Peng
用BzCN和Et 3 N作为催化剂保护完全未保护的β-d-葡萄糖-、β-d-奎诺-和β-d-吡喃木糖苷，分别直接和区域选择性地得到3，6-二-O-苯甲酰化的β-d-葡萄糖糖苷或3-O-苯甲酰化的β-d-奎诺-和β-d-吡喃木糖苷。此外，这些反式-反式三醇和四醇体系可以在BzCN作为苯甲酰化剂和催化量的4-吡咯烷基吡啶作为碱的存在下，在一锅反应中区域选择性地转化为它们相应的2-O-未保护的衍生物。因此，BzCN在催化量的胺碱存在下表现出作为酰化剂的独特性质，允许区域选择性保护常见的吡喃葡糖苷中存在的所有二醇、三醇和四醇立体结构。通过天然和非天然皂苷的简明合成，显示了一些衍生的结构单元的方便获得和巨大价值。
Protection of totally unprotected beta-d-gluco-, beta-d-quinovo- and beta-d-xylopyranosides with BzCN and Et3N as the catalyst afforded directly and regioselectively 3,6-di-O-benzoylated beta-d-glucopyranosides or 3-O-benzoylated beta-d-quinovo- and beta-d-xylopyranosides, respectively. Furthermore, these trans-trans triol and tetrol systems could be regioselectively transformed into their corresponding 2-O-unprotected derivatives in the presence of BzCN as the benzoylating agent and a catalytic amount of 4-pyrrolidinopyridine as a base in one-pot reactions. Hence, BzCN in the presence of a catalytic amount of an amine base exhibits unique properties as an acylating agent, permitting the regioselective protection of all diol, triol and tetrol stereostructures occurring in the commonly found glycopyranosides. The convenient access and great value of some of the derived building blocks are shown through the concise synthesis of natural and unnatural saponins.