β-Directing Effect of Electron-Withdrawing Groups at O-3, O-4, and O-6 Positions and α-Directing Effect by Remote Participation of 3-O-Acyl and 6-O-Acetyl Groups of Donors in Mannopyranosylations

Abstract

Section A: General Methods S10 Section B: Synthesis and characterization data Synthesis and characterization data for S1 S11 Synthesis and characterization data for S2 S12 Synthesis and characterization data for S3 S13 Synthesis and characterization data for S4 S14 Synthesis and characterization data for S5 S14 Synthesis and characterization data for 6 S15 Synthesis and characterization data for 7 S15 Synthesis and characterization data for 8 S16 Synthesis and characterization data for 1 S17 S2 Synthesis and characterization data for 2 S17 Synthesis and characterization data for 3 S18 Synthesis and characterization data for 4 S19 Synthesis and characterization data for 5 S19 Synthesis and characterization data for S6 S20 Synthesis and characterization data for S7 S21 Synthesis and characterization data for S8 S22 Synthesis and characterization data for S9 S22 Synthesis and characterization data for S10 S23 Synthesis and characterization data for S11 S23 Synthesis and characterization data for 9 S24 Synthesis and characterization data for 10 S25 Synthesis and characterization data for 11 S25 Synthesis and characterization data for 12 S26 Synthesis and characterization data for S12 S27 Synthesis and characterization data for S13 S27 Synthesis and characterization data for S14 S28 Synthesis and characterization data for S15 S29 Synthesis and characterization data for S16 S30 Synthesis and characterization data for S17 S31 Synthesis and characterization data for 13 S31 Synthesis and characterization data for 14 S32 Synthesis and characterization data for 15 S33 Synthesis and characterization data for 16 S33 References S88 Section C: 1 H NMR and 13 C NMR spectra 1 H NMR and 2D NMR spectra for 74 S202Section A: General Methods All reactions were conducted under a positive pressure of dry argon with dry, freshly distilled solvents unless otherwise noted. All reagents were purchased from commercial suppliers and used without further purification unless otherwise noted. Dichloromethane was distilled from calcium hydride. Flash column chromatography was performed employing 230-400 mesh silica gel. Thin-layer chromatography was Allyl 2,3,6-Tri-O-benzyl-4-O-(o-trifluoromethylbenzenesulfonyl)-D-mannopyranoside (S1). To a solution of allyl 2,3,6-tri-O-benzyl-D-mannopyranoside 1 (763 mg, 1.55 mmol) in CH 2 Cl 2 (10 mL) were added o-CF 3 PhSO 2 Cl (0.48 mL, 3.11 mmol), pyridine (0.50 mL, 6.22 mmol), and DMAP (38 mg, 0.311 mmol) at 0 o C. The resulting solution was stirred at 0 o C for 10 min and at room temperature for further 2 h. The reaction mixture was quenched with saturated aqueous NH 4 Cl, and then extracted with CH 2 Cl 2 . The combined organic layer was washed with 1N HCl and brine, dried over MgSO 4 , and concentrated in vacuo. The residue was purified by flash column chromatography

Characterization of glycosyl dioxolenium ions and their role in glycosylation reactions

“…The second set ( Fig. 2b) features benzyl ethers and benzoate esters (10)(11)(12)(13)(14)(15)(16)(17)(18) used in a matrix of model glycosylation reactions, as these represent the most commonly used protecting groups in synthetic carbohydrate chemistry. The benzyl ether and benzoate esters are structurally very similar, while differing significantly in electronic properties and their ability to stabilize an oxocarbenium ion 35,36 .…”

“…Importantly, LRP potentially allows for the utilization of the relative stereochemistry of C-3, C-4, or C-6 groups to control the facial selectivity in glycosylation reactions thereby enabling the stereoselective synthesis of C-2-deoxy and 1,2-cis glycosides. However, contradictory results have been reported and there is an ongoing debate as to the role and strength of this stereoelectronic effect [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] . Indirect proof for LRP has been derived from the stereochemical outcome of glycosylation reactions and studies using model systems 24 .…”

Methods Development for the Glycosylation and Microarraying of L-Rhamnose with Applications Toward the Automated Solution-Phase Synthesis of Homogalacturonan and Rhamnogalacturonan I

“…2-11). The choice of these electron withdrawing groups is inspired by the studies performed on mannose by Kim and co-workers (Baek et al, 2009). The L-rhamnose TCA donors with electron withdrawing groups at position O-4 are labeled type A and those with electron withdrawing groups at position O-3 are labeled type B.…”

“…Figure 2-12. Mannopyranosylation with electron withdrawing groups at O-3 (A) and O-4 (B) positions of D-mannose donors (Baek et al, 2009).…”

“…An elegant work using TCA donors of D-mannose with electron-withdrawing groups at the O-3, O-4 and O-6 positions was carried out by Kim and co-workers (Baek et al, 2009). In this study, both participating and non-participating electron withdrawing groups containing D-mannose trichloroacetimidate donors were synthesized and their glycosylation with a number of acceptors was carried out.…”