Stereoselective Synthesis of 2-(β-C-Glycosyl)glycals: Access to Unusual β-C-Glycosides from 3-Deoxyglycals

Abstract

A novel method for the highly stereoselective synthesis of β-(1→2)-C-saccharides employing 3-deoxy- and 3-C-branched glycals as hermaphroditic substrates is revealed. The generality of the C-C bond formation reaction between the two sugar units is evaluated. The developed methodology is successfully applied to the synthesis of biologically significant subunits that are present in various natural products, which include mixed C-disaccharides with adjacent THP-THF rings, C-aryl glycosides, and highly functionalized β-C-glycosides.

C-Glycopyranosyl Arenes and Hetarenes: Synthetic Methods and Bioactivity Focused on Antidiabetic Potential

“…A unique dimerization upon action of a Lewis acid on 3-deoxy- d -glucal ( 288 eq) or -galactal ( 288 ax) gave 2- C -glycosyl-glycals 289 (Scheme ), which were transformed by ozonolysis and deformylation into hemiketals 290 whose acidic treatment furnished C -glycosyl furans 291 …”

Synthesis of Carbon‐Branched Sugars Involving an Unprecedented 1,5‐ or 1,6‐Alkyl Transposition Reaction

“…Steel et al showed that 3,4,6‐tri‐ O ‐benzyl D‐glucal 1 in the presence of catalytic amount of acetyl perchlorate converts into a bicyclic acetal 3 through an unusual 1,7‐hydrogen shift . While carrying out this transformation using 3‐deoxy 4,6‐di‐ O ‐benzyl glycal 2 we have observed a stereoselective dimerization reaction which led to the formation of 2‐(β‐ C ‐glycosyl)‐glycal 4 (Scheme ). This typical reactivity of 3‐deoxy glycals under Lewis acid conditions prompted us to investigate further on the fate of oxocarbenium ion generated using these scaffolds.…”

Recent Advances in the Chemical Synthesis of C-Glycosides

“…Intriguingly, treatment of 3-deoxyglucal 209 with TMSOTf led to dimerization probably through the 3 H 4 half-chair conformer ( A ) of the glycal-derived oxocarbenium ion, affording β-(1 → 2)- C -glycoside 210 in 86% yield (Scheme ). Similarly, TMSOTf-promoted dimerization of 3-deoxygalactal 211 produced β-(1 → 2)- C -glycoside 212 in excellent yield (88%).…”

“…220,221 Reaction of 143 and 146 with unactivated aryl methyl ketones under the catalysis of tert-butyldimethylsilyl triflate (TBSOTf) in the presence of iPrNEt led to α-Cglycosides 154, 203, and 205 in moderate yields. 222 SnCl 4mediated coupling of glycals 143, 178, and 180 with titanium enolate derived from (S)-4-isopropyl-N-propanoyl-1,3-thiazolidine-2-thione afforded α-C-glycosides 206−208 as the predominant products in excellent yields (79−94%).223−225 The chiral auxiliary (R or S) determined the configuration of the newly formed stereocenters; switching the stereochemistry of the chiral auxiliary provided β-C-glycosides as the major anomers.223−225 Intriguingly, treatment of 3-deoxyglucal 209 with TMSOTf led to dimerization probably through the 3 H 4 half-chair conformer (A) of the glycal-derived oxocarbenium ion, affording β-(1 → 2)-C-glycoside 210 in 86% yield (Scheme 22) 226. Similarly, TMSOTf-promoted dimerization of 3-deoxygalactal 211 produced β-(1 → 2)-C-glycoside 212 in excellent yield (88%).…”