One‐Pot Synthesis of Hydrophobically Modified Iminosugar C ‐Alkynylglycosides: Facile Synthesis of Polyhydroxy Tetrahydroindolizines

Sugars in Multicomponent Reactions: A Toolbox for Diversity-Oriented Synthesis

Multicomponent reactions (MCRs) cover strategically employed chemical transformations that incorporate three or more reactants in one pot leading to a functionalized final product. Thus, it is an ideal tool to achieve high levels of complexity, diversity, yields of desired products, atom economy, and reduced reaction times. Sugars belong to the class of naturally occurring compounds with fascinating applications in the field of drug discovery due to the presence of various hydroxy groups and well-defined stereochemistry. However, their potential in MCRs has been realized only recently. This account describes recent advances in the synthesis of sugar-derived heterocycles synthesized by MCRs. We hope to encourage the synthetic and medicinal chemistry community to apply this powerful MCR chemistry to generate novel glycoconjugate challenges.

1 Introduction

2 Synthesis of Various Functionalized Sugar Compounds

2.1 Passerini and Ugi Multicomponent Reactions

2.2 Petasis Reaction

2.3 Hantzsch Reaction

2.4 Domino Ferrier–Povarov Reaction

2.5 Marckwald Reaction

2.6 Groebke–Blackburn–Bienaymé (GBB) Reaction

2.7 Prins–Ritter Reaction

2.8 Debus–Radziszewski Imidazole Synthesis Reaction

2.9 Mannich Reaction

2.10 A3-Coupling Reaction

2.11 [3+2]-Cycloaddition Reactions

2.12 Miscellaneous Reactions

3 Conclusion

Switching Electrophile Intermediates to Nucleophiles: Michael and Oxa-Diels-Alder Reactions to Afford Polyoxy-Functionalized Piperidine Derivatives with Tetrasubstituted Carbon

Michael, Michael-annulation, and oxa-Diels-Alder reactions of carbohydrate derivatives that afford polyoxy-functionalized piperidine derivatives bearing tetrasubstituted carbon at the 3-position of the piperidine ring are reported. Iminium ions generated from carbohydrate derivatives with amines were converted to enamines in situ, which acted as nucleophiles. As a result, substituents were introduced at the 3-position or both 2- and 3-positions of the piperidines bearing polyoxy groups. This strategy will be useful in drug discovery efforts.

Stereoselective synthesis of sugar mimetics from simple monosaccharides

A number of bicyclic imino- and carba-sugars (examples are presented in the Scheme) can be obtained from simple monosaccharides (hexoses or pentoses) by various methods.

Mannich Reactions of Carbohydrate Derivatives with Ketones To Afford Polyoxy-Functionalized Piperidines

Mannich reactions of carbohydrate derivatives with ketones that afford polyoxy-functionalized piperidines are reported. Ketone nucleophiles (enamines/enolates) were generated in the presence of the amines used for the formation of the iminium ions of sugar derivatives with or without an additive. Conditions to preferentially generate piperidine derivatives rather than tetrahydrofurans were identified. Products from the reactions of allyl ketones were readily transformed to bicyclic piperidines.

Glycoside Mimics from Glycosylamines: Recent Progress

Glycosylamines are valuable sugar derivatives that have attracted much attention as synthetic intermediates en route to iminosugar-C-glycosyl compounds. Iminosugars are among the most important glycomimetics reported to date due to their powerful activities as inhibitors of a wide variety of glycosidases and glycosyltransferases, as well as for their use as pharmacological chaperones. As they provide ready access to these important glycoside mimics, we have reviewed the most significant glycosylamine-based methodologies developed to date, with a special emphasis on the literature reported after 2006. The groups of substrates covered include N-alkyl- and N-benzyl-glycosylamines, N-glycosylhydroxylamines, N-(alkoxycarbonyl)-, and N-tert-butanesulfinyl-glycosylamines.

Iminosugar C-Nitromethyl Glycoside: Stereoselective Synthesis of Isoxazoline and Isoxazole-Fused Bicyclic Iminosugars

A simple and efficient method for the stereoselective synthesis of isoxazoline/isoxazole-fused iminosugar derivatives has been developed using intramolecular nitrile oxide cycloaddition (INOC) as a key step. Iminosugar C-nitromethyl glycosides, derived from simple carbohydrates, served as excellent nitrile oxide precursors in 1,3-dipolar cycloaddition reactions. N-Alkenyl iminosugar C-nitromethyl glycosides afforded novel isoxazoline-fused indolizidine-, pyrrolizidine-, and quinolizidine-based iminosugars in excellent yields with a high degree of stereoselectivity, whereas N-alkynyl iminosugar C-nitromethyl glycosides furnished the corresponding isoxazole containing tricyclic iminosugars in very good yields.