3‐ and 4‐Uloses Derived from N‐Acetyl‐D‐glucosamine: A Unique Pair of Complementary Organocatalysts for Asymmetric Epoxidation of Alkenes

Abstract

The 4-ulose and the 3-ulose, both derived in two steps from the a-methyl glycoside of Nacetyl-d-glucosamine (GlcNAc), act as organocatalysts in the asymmetric epoxidation of alkenes, with unprecedented complementary enantioselectivity. The best results are found with a,b-unsaturated esters as substrates, with enantiomeric ratios up to 90:10 and 11:89, respectively.Typical Epoxidation Protocol, trans-1-Acetoxy-2,3epoxy-3-phenylpropane (Table 2, entry 5) Cinnamyl acetate (88.1 mg, 0.50 mmol) was dissolved in acetonitrile and aqueous Na 2 EDTA solution (10 À4 M, 2 mL each) and Bu 4 NHSO 4 (15 mg) were added with vigorous stirring at 28 8C. A small portion of a mixture of oxone (1.537 g, 2.5 mmol) and NaHCO 3 (0.651 g, 7.75 mmol) was added to the mixture to bring the pH to > 7. Then the 4-Scheme 4. Overall yields of the catalysts 5 and 6. 794

NHC‐Catalyzed Hydroacylation of Styrenes

“…(3)], the first intermolecular NHC-catalyzed hydroacylation of unstrained, rather electron-neutral alkenes. This transformation is remarkable as the organocatalyzed transformation of electron-neutral alkenes such as styrenes is a long-standing challenge in organocatalysis; only some rare examples of organocatalyzed epoxidations [11] and organocatalyzed brominations, [12] and a few examples relying on radical mechanisms have been reported. [13] Recently, we designed a family of novel NHCs bearing a 2,6-dimethoxyphenyl moiety.…”

Regioselective Manipulation of GlcNAc Provides Allosamine, Lividosamine, and Related Compounds

“…Five g of this mixture was purified by flash chromatography on a 120 g silica cartridge with DCM/MeOH, and increasing ratio of MeOH from 0 to 20% in 50 min, the product eluted at 14% MeOH to afford pure methyl 2-acetamido-2-deoxy- d -glucopyranoside as white solid (2.37 g, yield: 47%) mp 188–189 °C (lit. 36 186–188 °C); 1 H NMR (400 MHz, methanol- d 4 ) δ 4.65 (d, J = 3.5 Hz, 1H), 3.90 (dd, J = 10.7, 3.6 Hz, 1H), 3.83 (dd, J = 11.9, 2.4 Hz, 1H), 3.69 (dd, J = 11.9, 5.7 Hz, 1H), 3.63 (dd, J = 10.7, 8.7 Hz, 1H), 3.54 (ddd, J = 10.0, 5.7, 2.4 Hz, 1H), 3.37 (s, 3H), 3.36–3.32 (m, 1H), 1.98 (s, 3H); 13 C{ 1 H} NMR (101 MHz, methanol- d 4 ) δ 173.8, 100.0, 73.8, 73.1, 72.5, 62.9, 55.6, 55.5, 22.7. HRMS (ESI-TOF) m / z : [M + H] + and [M + Na] + Calcd for C 9 H 18 NO 6 236.1129 and C 9 H 17 NO 6 Na 258.0954; found 236.1132 and 258.0953.…”

“…A suspension of N -acetyl glucosamine (10 g, 0.045 mol) and dry Amberlite IR 120H + (12 g) in MeOH (300 mL) was heated at reflux for 48 h. Upon cooling, the Amberlite resin was removed by filtration, and the methanol removed in vacuo to provide the product 9.98 g as a mixture of α and β, yield: 94%, as a white solid (α:β = 9.8:1). Five g of this mixture was purified by flash chromatography on a 120 g silica cartridge with DCM/MeOH, and increasing ratio of MeOH from 0 to 20% in 50 min, the product eluted at 14% MeOH to afford pure methyl 2-acetamido-2-deoxy- d -glucopyranoside as white solid (2.37 g, yield: 47%) mp 188–189 °C (lit . 186–188 °C); 1 H NMR (400 MHz, methanol- d 4 ) δ 4.65 (d, J = 3.5 Hz, 1H), 3.90 (dd, J = 10.7, 3.6 Hz, 1H), 3.83 (dd, J = 11.9, 2.4 Hz, 1H), 3.69 (dd, J = 11.9, 5.7 Hz, 1H), 3.63 (dd, J = 10.7, 8.7 Hz, 1H), 3.54 (ddd, J = 10.0, 5.7, 2.4 Hz, 1H), 3.37 (s, 3H), 3.36–3.32 (m, 1H), 1.98 (s, 3H); 13 C­{ 1 H} NMR (101 MHz, methanol- d 4 ) δ 173.8, 100.0, 73.8, 73.1, 72.5, 62.9, 55.6, 55.5, 22.7.…”

“…The catalyst [(neocuproine)­PdOAc] 2 OTf 2 (57 mg, 2.5 mol %) was added, and the mixture was stirred at room temperature for 1 h. Upon completion of the reaction (according to TLC), water (70 mL) was added, and the mixture was lyophilized to afford the crude product. Subsequent purification by flash chromatography on a 12 g silica cartridge with DCM/MeOH, increasing ratio of MeOH from 0 to 7% in 21 min, the product eluted at 4% MeOH to afford a white solid (346 mg, 74%), mp 161–162 °C (lit . 164 °C); 1 H NMR (400 MHz, Methanol- d 4 ) δ 5.09 (d, J = 4.1 Hz, 1H), 4.88 (dd, J = 4.1, 1.2 Hz, 1H), 4.29 (dd, J = 9.8, 1.3 Hz, 1H), 3.89 (dd, J = 12.1, 2.3 Hz, 1H), 3.82 (dd, J = 12.1, 4.6 Hz, 1H), 3.73–3.67 (m, 1H), 3.39 (s, 3H), 2.03 (s, 3H); 13 C­{ 1 H} NMR (101 MHz, methanol- d 4 ) δ 203.8, 173.7, 102.4, 77.0, 73.8, 62.6, 60.3, 55.8, 22.4; HRMS (ESI-TOF) m / z : [M + H] + and [M + Na] + Calcd for C 9 H 16 NO 6 234.0972 and C 9 H 15 NO 6 Na 256.0797; found 234.0973 and 256.0793.…”

“…Five g of this mixture was purified by flash chromatography on a 120 g silica cartridge with DCM/MeOH, and increasing ratio of MeOH from 0 to 20% in 50 min, the product eluted at 14% MeOH to afford pure methyl 2-acetamido-2-deoxy-D-glucopyranoside as white solid (2.37 g, yield: 47%) mp 188−189 °C (lit. 36 186−188 °C); 1 H NMR (400 MHz, methanol-d 4 ) δ 4.65 (d, J = 3.5 Hz, 1H), 3.90 (dd, J = 10.7, 3.6 Hz, 1H), 3.83 (dd, J = 11.9, 2.4 Hz, 1H), 3.69 (dd, J = 11.9, 5.7 Hz, 1H), 3.63 (dd, J = 10.7, 8.7 Hz, 1H), 3.54 (ddd, J = 10.0, 5.7, 2.4 Hz, 1H), 3.37 (s, 3H), 3.36−3.32 (m, 1H), 1.98 (s, 3H); 13 Methyl 2-Acetamido-2-deoxy-α-D-glucopyran-3-ulose (3). Methyl 2-acetamido-2-deoxy-α-D-glucopyranoside 2 (474 mg, 2 mmol) and benzoquinone (324 mg, 3 mmol) were dissolved in DMSO (6.6 mL).…”