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With 4,5-dichloroimidazole; In dichloromethane; at 20℃; for 1.75h;
A mixture of 2, 3,4, 6-tetra-D-benzyl-D-mannose (Koto et al., 1976) (940 mg, 1.74 mmol), dimethoxy-N, N-diisopropylphosphoromidate (437 mg, 2.27 mmol) and 4,5-dichloroimidazole (355 mg, 2.61 mmol) in dry dichloromethane (25 mL), under nitrogen, was stirred at room temperature for 105 min. The mixture was poured into water (100 mL) and extracted with dichloromethane. The organic layer was washed with water, dried over magnesium sulfate and the solvent was removed. The residue consisting mainly of phosphite 10 was used without further purification.
2,3,4,6-tetra-O-benzyl-D-mannopyranosyl dimethyl phosphite[ No CAS ]
Yield
Reaction Conditions
Operation in experiment
1H-Tetrazole (0.25 g, 3.6 mmol) was addedto a solution of the reducing sugar S5 (1.6g, 3.0 mmol) and i-Pr2NP(OMe)2(0.55 mL, 2.4 mmol) in dry CH2Cl2 (6.0 mL) at 0 C. Themixture was stirred for 5 min and warmed to rt. After being stirred for 45 min,the reaction was quenched with a saturated NaHCO3 aqueous solution(12 mL). The mixture was extracted with CH2Cl2 (100 mL)and the organic layer was washed with saturated NaHCO3 aqueoussolutions (3 × 100 mL). The aqueous layer was then back-extracted with CH2Cl2(100 mL). The combined organic layers were dried over Na2SO4,filtered and concentrated under reduced pressure. The residue was dissolved in freshlydistilled THF (15 mL) and a solution of BH3?THF (0.99 M, 9.0 mL, 8.9mmol) was added to the solution at 0 C. The reaction mixture was stirred for 5min and warmed to rt. After being stirred for 4.5 h, the mixture was concentratedunder reduced pressure. The residue was then dissolved in CHCl3 (100mL) and successively washed with saturated NaHCO3 aqueous solutions(2 × 100 mL) and a brine (100 mL). The aqueous layer was back-extracted withCHCl3 (100 mL). The combined organic layers were dried over Na2SO4,filterd and concentrated under reduced pressure. Purification of the residue bysilica gel column chromatography [hexane-AcOEt (7:1, v/v)] gave8 (1.6 g, 2.4 mmol, quant, a:b = 90:10) as a colorless syrup. The 1Hand 31P NMR spectra were in good agrrement with the reported data.1