Orthogonal Activation of Propargyl and n-Pentenyl Glycosides and 1,2-Orthoesters

Abstract

An orthogonal activation strategy with propargyl and n-pentenyl glycosides has been identified. According to this methodology, n-pentenyl glycosides can be selectively activated with NIS/TMSOTf in the presence of either armed or disarmed propargyl O-glycosides. In addition, we report herein that propargyl 1,2-orthoesters can be selectively activated with AuBr(3) in CH(2)Cl(2) at room temperature in the presence of n-pentenyl glycosides. Similarly, pentenyl 1,2-orthoesters can be selectively activated with NIS/Yb(OTf)(3) in the presence of propargyl glycosides.

Chapter 8. Recent advances in gold-catalyzed glycosylation

“…16 Later, they found AuBr 3 selectively activated propargyl 1,2-orthoesters in presence of propargyl glycoside, propargyl ethers 17 and n-pentenyl glycosides. 18 Hotha and co-workers successfully applied propargyl 1,2-orthoesters in the stereoselective synthesis of 1,2-trans glycosyl amino acids 19 and interesting glycomonomers. 20 They also employed AuBr 3 -catalyzed selective activation of propargyl 1,2-orthoester in the presence of propargyl glycoside as a key step to the synthesis of tetrasaccharide motif of the Leishmania donovani lipophosphoglycan.…”

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

“…24–27 Yet this strategy remains somewhat under-developed with too few known examples to become universally applicable. Only the following examples are known to date: the original S -phenyl vs fluoride introduced by Kanie et al, 24,25,28 thioimidate-based approaches developed in our lab, 19,29–31 Hotha’s O -pentenyl vs O -propargyl, 32 and O -allylphenyl-based approach also introduced by our group. 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.…”

p-Nitrophenyl carbonate promoted ring-opening reactions of DBU and DBN affording lactam carbamates

“…The 3,4-dimethylphenyl p -nitrophenyl carbonate ( 9a ) and geranyl carbonate 10a gave the corresponding γ-lactams 9b and 10b in 62% and 46% yields, respectively. Similarly, the p -nitrophenyl carbonate of D-psicofuranose [28], n -pentenyl 2,3,4-tri- O -benzyl-α-D-mannopyranoside [32–34] and 2,3-di- O -benzyl-α-methyl-D-arabinofuranoside [35] (Table 2, 11a–13a) gave the γ-lactam-derived carbamates 11b–13b in 53%, 63% and 67% yield, respectively.…”