title: Gold(I)-catalyzed glycosylation with glycosyl ortho-alkynylbenzoates as donors: general scope and application in the synthesis of a cyclic triterpene saponin.
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 alpha-selective glycosylation with a 2-deoxy sugar donor and beta-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.
authors.affiliation: State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China.
authors.forename: Yao
authors.initials: Y
authors.lastname: Li
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Yang
authors.forename: Yunpeng
authors.initials: Y
authors.lastname: Liu
authors.forename: Cunsheng
authors.initials: C
authors.lastname: Zhu
authors.forename: You
authors.initials: Y
authors.lastname: Yang
authors.forename: Biao
authors.initials: B
authors.lastname: Yu
mesh_terms: D002384:Catalysis; D005947:Glucose; D006031:Glycosylation; D006046:Gold / Q000737:chemistry*; D009579:Nitrobenzoates / Q000737:chemistry*; D009844:Oligosaccharides / Q000138:chemical synthesis; D012503:Saponins / Q000138:chemical synthesis; D013237:Stereoisomerism; D014315:Triterpenes / Q000737:chemistry
chemical_list: D009579:Nitrobenzoates; D009844:Oligosaccharides; D012503:Saponins; D014315:Triterpenes; D006046:Gold; D005947:Glucose