1,2-O-Isopropylidene-5-O-(triphenylmethyl)-alpha-D-ribofuranose synthesis

Yield:20590-57-2 99%

Reaction Conditions:

with sodium tetrahydroborate in ethanol;dichloromethane at 0 - 20; for 0.5 h;Inert atmosphere;

Steps:

b 4.1.1 1,2-O-Isopropylidene-5-O-trityl-α-d-ribofuranose (12)

IBX was added to a solution of 11 [12b] (10.8g, 0.025mol) in MeCN (230mL) and the resulting mixture was heated at reflux for 5h. After cooling to room temperature, the solid parts were filtered off, and the filtrate was concentrated in vacuo. Chromatography of the residue on silica gel (n-hexane/ethyl acetate, 5:1) gave 10.0g (93%) of 1,2-O-isopropylidene-5-O-trityl-α-d-erythro-pentofuranos-3-ulose [13] as a white amorphous solid; [α]_D²⁶+123.5 (c 0.20, CHCl₃), lit [13]. [α]_D+132 (c 4.7, CHCl₃, temperature at 21-22°C). IR (neat) υ_max 1010, 1077, 1152, 1215, 1375, 1448, 1489, 1773cm^-1; ¹H NMR (600MHz, CDCl₃): δ 1.47 (s, 6H, 2×CH₃), 3.32 (dd, 1H, J=2.6Hz, J=10.1Hz, H-5), 3.50 (dd, 1H, J=2.4Hz, J=10.1Hz, H-5), 4.41 (m, 1H, H-4), 4.54 (dd, 1H, J=1.0Hz, J=4.5Hz, H-2), 6.33 (d, 1H, J=4.5Hz, H-1), 7.23-7.25 (m, 3H, Ph), 7.28-7.31 (m, 6H, Ph), 7.34-7.36 (m, 6H, Ph); ¹³C NMR (100MHz, CDCl₃): δ 27.2 (CH₃), 27.7 (CH₃), 64.4 (C-5), 76.9 (C-2), 80.0 (C-4), 87.4 (C_q), 103.6 (C-1), 114.2 (C_q), 127.2 (3×CH_Ph), 127.9 (6×CH_Ph), 128.6 (6×CH_Ph), 143.2 (3×C_i), 210.2 (C-3). Anal. Calcd for C₂₇H₂₆O₅: C, 75.33; H, 6.09. Found: C, 75.20, H, 6.18. To a solution of the obtained ulose [13] (9.9g, 0.023mol) in a mixture of EtOH/CH₂Cl₂ (378mL, 8:1) that had been pre-cooled to 0°C was added NaBH₄ (1.74g, 0.046mol). After stirring at 0°C for 10min and another 20minat room temperature, the solvents were evaporated, and the residue was partitioned between CH₂Cl₂ (290mL) and brine (340mL). The separated aqueous layer was then washed with CH₂Cl₂ (2×290mL). The combined organic extracts were dried over Na₂SO₄, the solvent was evaporated, and the residue was subjected to flash chromatography on silica gel (n-hexane/ethyl acetate, 5:1) to afford 9.85g (99%) of compound 12 as a white foam; [α]_D²⁶+25.5 (c 0.20, CHCl₃); lit [13]. [α]_D+25.8 (c 4.5, CHCl₃, temperature at 21-22°C). IR (neat) υ_max 1011, 1064, 1114, 1163, 1213, 1373, 1447, 1490cm^-1; ¹H NMR (400MHz, CDCl₃): δ 1.38 (s, 3H, CH₃), 1.57 (s, 3H, CH₃), 2.31 (d, 1H, J=9.6Hz, OH), 3.27 (dd, 1H, J=4.8Hz, J=10.4Hz, H-5), 3.41 (dd, 1H, J=3.0Hz, J=10.4Hz, H-5), 3.88-4.00 (m, 2H, H-3, H-4), 4.57-4.59 (m, 1H, H-2), 5.88 (d, 1H, J=3.8Hz, H-1), 7.21-7.26 (m, 3H, Ph), 7.27-7.32 (m, 6H, Ph), 7.44-7.48 (m, 6H, Ph); ¹³C NMR (100MHz, CDCl₃): δ 26.5 (CH₃), 26.6 (CH₃), 63.0 (C-5), 72.3 (C-3), 78.5(C-2), 79.8 (C-4), 86.7 (C_q), 104.2 (C-1), 112.6 (C_q), 127.0 (3×CH_Ph), 127.8 (6×CH_Ph), 128.7 (6×CH_Ph), 143.8 (3×C_i). Anal. Calcd for C₂₇H₂₈O₅: C, 74.98; H, 6.53. Found: C, 74.82; H, 6.64.

References:

Jacková, Dominika;Martinková, Miroslava;Gonda, Jozef;Stanková, Kvetoslava;Bago Pilátová, Martina;Herich, Peter;Ko?í?ek, Jozef [Carbohydrate Research,2017,vol. 451,p. 59 - 71]