IPy₂BF₄-Mediated Transformation of n-Pentenyl Glycosides to Glycosyl Fluorides:  A New Pair of Semiorthogonal Glycosyl Donors

Abstract

Bis(pyridinium) iodonium(I) tetrafluoroborate (IPy2BF4), a solid and stable reagent, can be used to transform n-pentenyl orthoesters (NPOEs) and n-pentenyl glycosides (NPGs) into glycosyl fluorides. The latter pair constitutes a new set of semiorthogonal glycosyl donors that can be used in glycosylation strategies, alone or in combination with NPOEs.

S-Benzimidazolyl (SBiz) Imidates as a Platform for Oligosaccharide Synthesis via Active–Latent, Armed–Disarmed, Selective, and Orthogonal Activations

“…33 Likewise, we reported a related, albeit less flexible, semiorthogonal approach using S -ethyl vs O -pentenyl, 34 which was extended to fluoride vs O -pentenyl by Fraser-Reid and Lopez. 35 …”

Expeditious oligosaccharide synthesis via selective, semi-orthogonal, and orthogonal activation

“…demonstrated that n -pentenyl glycosides can be selectively activated over glycosyl fluoride acceptors (vide infra). 88 More recently, Hotha et al observed that n -pentenyl glycoside 84 could be activated over propargyl glycosyl acceptor 85 in the presence of NIS/TMSOTf (Scheme 18b). 89 …”

“…135 Lopez et al reported that n -pentenyl 1,2-orthoesters are activated over glycosyl fluoride acceptors in the presence NIS and Yb(OTf) 3 . 88 Recently, Hotha et al reported that n -pentenyl 1,2-orthoester 139 can be selectively activated over propargyl glycoside 85 in the presence of NIS/Yb(OTf) 3 (Scheme 27b). 89 Along similar lines, propargyl 1,2-orthoester 141 can be selectively activated over n -pentenyl acceptor 142 in the presence of AuBr 3 leading to trisaccharide 143 (Scheme 27c).…”

“…88 While either armed or disarmed glycosyl fluorides underwent glycosylation with armed/disarmed n -pentenyl glycoside in presence of Yb(OTf) 3 , only armed n -pentenyl glycosides could be activated over disarmed glycosyl fluorides in presence of IDCP. As depicted in Scheme 34, fluoride donor 177 was selectively activated over pentenyl 178 in the presence of Yb(OTf) 3 .…”

2-Allylphenyl glycosides as complementary building blocks for oligosaccharide and glycoconjugate synthesis

“…A very promising orthogonality was shown for O- pentenyl versus O- propargyl glycosides by Hotha et al [17] and for S- glycosyl O- methyl phenylcarbamothioate (SNea) versus thioglycosides/thioimidates by us [18], but still their applicability to multistep synthesis remains to be proven. Working to expand this concept, our group reported a related, albeit less flexible, semiorthogonal approach with the use of S- ethyl and O- pentenyl leaving groups [19], which was later extended to fluoride/ O- pentenyl combination by Fraser-Reid and Lopez [20]. Oxygen- [21] and sulfur-based [22] leaving groups fit into many expeditious strategies for oligosaccharide synthesis [6].…”