反应详情

Powdered potassium hydroxide (25 g.) was added to a magnetically stirred solution of syrupy methyl L-glucopyranoside (4.8 g.) in dry 1,4-dioxane (30 ml.). This stirred solution was gently heated on an oil bath (reflux), and freshly distilled benzyl chloride (32 ml.) was added dropwise over a 1 hour period. Heating and stirring were continued for an additional 4 hour period, at which time the dioxane was distilled and the resultant mixture cooled, diluted with water (200 ml.) and extracted with chloroform (3×75 ml.). The chloroform extracts were then washed with dilute hydrochloric acid and then with water. The chloroform layer was dried over sodium sulfate and then concentrated at reduced pressure to a syrup (17 g.) which was seen to contain three components (t.l.c., benzene/ethyl acetate 10:1 v/v) having Rf values of approximately 0.4, 0.48, and 0.73. T.L.C. comparison (benzene/ethyl acetate 10:1 v/v) of this mixture with the previously prepared methyl 2,3,4,6-tetra-O-benzyl-D-glucopyranosides and also with benzyl ether showed that the component with the greatest mobility was benzyl ether whereas the one having the least mobility was likely the α-anomer and the middle component the β-anomer. A small portion of this reaction mixture was purified by column chromatography on silica gel by eluting first with benzene to remove benzyl ether and then with a 10:1 mixture of benzene-ethyl acetate to give methyl 2,3,4,6-tetra-O-benzyl-α-L-glucopyranoside as a syrup having [α]D -25.4° (c 3.8, chloroform) as compared with [α]D +23.8° (c 3.42, chloroform), or [α]D +18.7° (c 1.5, chloroform) for methyl 2,3,4,6-tetra-O-benzyl-α-D-glucopyranoside, and crystalline methyl 2,3,4,6-tetra-O-benzyl-β-L-glucopyranoside having m.p. 69.5°-70°, [α]D -12.1° (c 4.2, dioxane) as compared to m.p. 68°-69°, [α]D +11° (c 5.3, dioxane) for methyl 2,3,4,6-tetra-O-benzyl-β-D-glucopyranoside.

1. temperatureThis stirred solution was gently heated on an oil bath
2. additionwas added dropwise over a 1 hour period
3. temperatureHeating
4. distillationthe dioxane was distilled
5. temperaturethe resultant mixture cooled
6. additiondiluted with water (200 ml.)
7. extractionextracted with chloroform (3×75 ml.)
8. washThe chloroform extracts were then washed with dilute hydrochloric acid
9. dry with materialThe chloroform layer was dried over sodium sulfate
10. concentrationconcentrated at reduced pressure to a syrup (17 g.) which
11. customA small portion of this reaction mixture was purified by column chromatography on silica gel
12. washby eluting first with benzene
13. customto remove benzyl ether
14. additionwith a 10:1 mixture of benzene-ethyl acetate