Development of α-Selective Glycosylation with l-Oleandral and Its Application to the Total Synthesis of Oleandrin,Organic Letters

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Development of α-Selective Glycosylation with l-Oleandral and Its Application to the Total Synthesis of Oleandrin
Organic Letters ( IF 4.9 ) Pub Date : 2023-02-05 , DOI: 10.1021/acs.orglett.2c04358
Nolan Carney ₁ , Natasha Perry ₂ , Jacob Garabedian ₂ , Pavel Nagorny ₂

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This letter describes the development of an α-selective glycosylation using l-oleandrose, a 2-deoxysugar that is frequently found in natural products, and its application to the total synthesis of the natural cardiotonic steroids oleandrin and beaumontoside. To improve the reaction diastereoselectivity and to minimize side-product formation, an extensive evaluation and optimization of the conditions leading to α-selective glycosylation of digitoxigenin with l-oleandrose-based donors was conducted. These studies led to the exploration of 8 different phosphine·acid complexes or salts and yielded HBr·PPh₃ as the optimal catalyst, which provided in the cleanest α-glycosylation and produced protected beaumontoside in 67% yield. Subsequent application of these conditions to synthetic oleandrigenin afforded the desired α-product in 69% isolated yield─enabling the completion of the first synthesis of oleandrin in 17 steps (1.2% yield) from testosterone.

中文翻译：

l-夹竹桃醛α-选择性糖基化的研究进展及其在夹竹桃苷全合成中的应用

这封信描述了使用l-夹竹桃糖（一种常见于天然产物中的 2-脱氧糖）进行α-选择性糖基化的开发，及其在天然强心类固醇夹竹桃苷和 Beaumontoside 的全合成中的应用。为了提高反应非对映选择性并尽量减少副产物的形成，对洋地黄毒苷与基于 l-夹竹桃糖的供体进行 α-选择性糖基化的条件进行了广泛的评估和优化。这些研究导致了对 8 种不同的膦·酸络合物或盐的探索，并产生了 HBr·PPh ₃作为最佳催化剂，它提供了最干净的 α-糖基化，并以 67% 的收率产生了受保护的博蒙托苷。随后将这些条件应用于合成夹竹桃苷元，以 69% 的分离产率提供了所需的 α-产物 — 从而能够通过 17 个步骤完成夹竹桃苷的首次合成（产率 1.2%）。

更新日期：2023-02-05

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