(2R,3S,4R,5R,6S)-6-(羟甲基)氧烷-2,3,4,5-四醇

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: A mixture of α-L-glucopyranose (5.4 g.), methanol (30 ml.) and cation-exchange resin [(2 g., Dowex® 50W-X8 (H+), 50-100 mesh, previously prepared by treatment with methanol] was stirred magnetically at reflux temperature for 24 hours in a 50-ml. round-bottomed flask. The solution, which gave a negative test, was then cooled and filtered. The resin was washed several times with methanol and the filtrate and washings were evaporated at reduced pressure to a syrup (5.63 g., 96%) containing no L-glucose (paper chromatography, n-butanol/ethanol water v/v 40:11:19). A sample (1.0 g.) was dissolved in boiling methanol (2 ml.) and the mixture was allowed to slowly cool to room temperature to give crystalline methyl L-glucopyranoside. The crystals were suspended in enough ethanol to make a 10% (w/v) mixture, and this mixture was boiled to effect dissolution. On cooling of the mixture pure methyl α-L-glucopyranoside was obtained, m.p. 166.5°-168°, [α]D -156° (c 2.5, water). These values compare favourably with those for methyl α-D-glucopyranoside, m.p. 167°-169°, [α]D +157° (c 2, water). at reflux temperature for 24 hours in a 50-ml The solution, which gave a negative test was then cooled filtered The resin was washed several times with methanol the filtrate and washings were evaporated at reduced pressure to a syrup (5.63 g., 96%) containing no L-glucose (paper chromatography, n-butanol/ethanol water v/v 40:11:19) A sample (1.0 g.) was dissolved

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: 1-Deoxy-1-nitro-L-glucitol (5.0 g.) was dissolved in 2 N sodium hydroxide (15 ml.) and the solution was immediately added dropwise to a stirred, cooled (ice-bath) solution of sulfuric acid (7.5 ml.) in water (9.0 ml.). The solution was then diluted with water (175 ml.) and neutralized to Congo Red with warm barium hydroxide solution. The precipitated barium sulfate was removed by centrifugation and the remaining sulfate was precipitated with a slight excess of barium acetate. The solution was then filtered through a pad of Celite® and the filtrate de-ionized by passage through a column containing 50 ml. of Dowex® 50W-X8 (H+) resin. The effluent and washings were evaporated under reduced pressure to a syrup which was diluted with a few drops of ethanol, warmed to 50°, seeded (seed crystals obtained from previous experiments) and allowed to crystallize. The resulting crystals were filtered with the aid of cold ethanol to give, after recrystallization, α-L-glucopyranose (2.4 g.), m.p. 146°-147°, [α]D -100°→-53.3° (24 hr.; c 2.15, water), compared to m.p. 146°-147°, [α]D -53° (at equilibrium; c 2.6, water). The filtrate containing L-glucose (t.l.c., n-propanol/ethyl acetate/water v/v 3:1:1) was retained for use in subsequent preparations of L-glucose. the solution was immediately added dropwise to a stirred The precipitated barium sulfate was removed by centrifugation the remaining sulfate was precipitated with a slight excess of barium acetate The solution was then filtered through a pad of Celite® the filtrate de-ionized by passage through a column containing 50 ml The effluent and washings were evaporated under reduced pressure to a syrup which was diluted with a few drops of ethanol warmed to 50° (seed crystals obtained from previous experiments) to crystallize The resulting crystals were filtered with the aid of cold ethanol to give after recrystallization, α-L-glucopyranose (2.4 g.), m.p. 146°-147°, [α]D -100°→-53.3° (24 hr.; c 2.15, water) The filtrate containing L-glucose (t.l.c

反应条件: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

实验步骤: α-L-glucopyranose; β-L-glucopyranose; α-L-glucofuranose; β-L-glucofuranose