Gold(I)-catalyzed glycosylation with glycosyl ortho-alkynylbenzoates as donors: general scope and application in the synthesis of a cyclic triterpene saponin.
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.
Li
Yao
Y
State Key Laboratory of Bioorganic and Natural Products Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China.
Yang
Xiaoyu
X
Liu
Yunpeng
Y
Zhu
Cunsheng
C
Yang
You
Y
Yu
Biao
B
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
D009579:Nitrobenzoates; D009844:Oligosaccharides; D012503:Saponins; D014315:Triterpenes; D006046:Gold; D005947:Glucose