Gold(I)-Catalyzed Glycosylation with Glycosyl ortho-Alkynylbenzoates as Donors: General Scope and Application in the Synthesis of a Cyclic Triterpene Saponin
✍ Scribed by Yao Li; Xiaoyu Yang; Yunpeng Liu; Cunsheng Zhu; You Yang; Biao Yu
- Publisher
- John Wiley and Sons
- Year
- 2010
- Tongue
- English
- Weight
- 479 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
Glycosyl ortho‐alkynylbenzoates have emerged as a new generation of donors for glycosidation under the catalysis of gold(I) complexes such as Ph~3~PAuOTf and Ph~3~PAuNTf~2~ (Tf=trifluoromethanesulfonate). A wide variety of these donors, including 2‐deoxy sugar and sialyl donors, are easily prepared and shelf stable. The glycosidic coupling yields with alcohols are generally excellent; even direct coupling with the poorly nucleophilic amides gives satisfactory yields. Moreover, excellent α‐selective glycosylation with a 2‐deoxy sugar donor and β‐selective sialylation have been realized. Application of the present glycosylation protocol in the efficient synthesis of a cyclic triterpene tetrasaccharide have further demonstrated the versatility and efficacy of this new method, in that a novel chemoselective glycosylation of the carboxylic acid and a new one‐pot sequential glycosylation sequence have been implemented.