Stereocontrolled Glycosyl Transfer Reactions with Unprotected Glycosyl Donors

Abstract

I. Introduction 4443 II. Challenges of Glycoside Synthesis 4444 III. Brief Survey of Post-1980 Methods of Anomeric Activation 4444 1. Non-Bromide, -Chloride, -Iodide Methods for Anomeric Activation 4444 2. New Generations of Anomeric Leaving Groups and Activation Methods 4445 IV. Glycosylation with Unprotected Glycosyl Donors 4446 1. O-Glycosides 4446 A. Fischer-type Glycosylation of Alcohols 4446 B. Miscellaneous Methods 4447 2. Glycosylamines and Glycosyl Azides 4447 3. C-Glycosides 4448 V. Remote Activation Concept 4448 VI. Stereocontrolled Glycosylation Using 3-Methoxypyridyl (MOP) O-Unprotected Glycosyl Donors 4449 1. Design, Concept, and Activation Mechanism 4449 2. Preparation of MOP Glycosyl Donors 4451 3. Glycosylation with O-Unprotected MOP Glycosyl Donors 4452 A. Synthesis of O-Glycosides and Oligosaccharides 4452 B. Selective Activation 4453 C. Stereocontrolled Synthesis of Glycosyl 1-Carboxylates and Glycosyl Azides 4456 D. Stereocontrolled Synthesis of Glycosyl 1-Phosphates and Glycosyl Nucleotides 4457 4. Solid-Phase Synthesis Using MOP Donors and Acceptors 4458 A. Linking Strategy 4458 B. Synthesis of O-Glycosides and Oligosaccharides on Solid Support 4459 VII. Conclusion 4460 VIII. Acknowledgments 4461 IX. References 4461

In situ formation of C-glycosides during electrospray ionization tandem mass spectrometry of a series of synthetic amphiphilic cholesteryl polyethoxy neoglycolipids containing N-acetyl-D-glucosamine

“…The synthesis of the neoglycolipid derivatives was performed as reported [8,9]. The molecular structures of these derivatives are shown in Scheme 1.…”

“Active–Latent” Thioglycosyl Donors and Acceptors in Oligosaccharide Syntheses

“…Under similar 1 H-NMR spectrum of 61 was less informative in confirming the regiochemistry of the newly introduced glycosidic linkage of 61. However, the regiochemistry could be unambiguously confirmed from its 13 C NMR spectrum which showed a deshielded signal for C-3 0 at d 81.1 ppm (Dd ¼ þ8.0 ppm) compared to d 73.1 ppm for C-3 0 of its precursor 60. The application of thioglycoside gained a new impetus by the finding of Kahne et al [56] who observed that phenylsulfenyl glycosyl donors, readily accessible by oxidation (mCPBA) of phenyl thioglycosides, can be effectively glycosylated using triflic anhydride as activator.…”

Recent Advances in Heterolytic Nucleofugal Leaving Groups

“…84 The use of leaving groups that are activated at an atom that is not directly attached to the anomeric center of a glycosyl donor has been defined as remote activation (recently reviewed). 85 In recent years, a new glycosylation strategy that allows chemoselective activation of an S-thiazolyl (STaz) leaving group of a glycosyl substrate has been developed. This principle can be illustrated with donor glycosyl substrate 93 (scheme 35).…”