Dimethylformamide → (2R,3R,4S,5R,6R)-3,4,5-Tris(benzyloxy)-2-bromo-6-(3-phenylpropyl)tetrahydro-2H-pyran

Beteiligte Stoffe

Reaktionsbedingungen

Reaktionsschritte

2,3,4,6-Tetra-O-benzyl-D-glucopyranose (1.0 g, 1.9 mmol) was dissolved in anhydrous DCM (6 mL) and anhydrous DMF (0.4 mL) under argon. The resulting solution was stirred at 0° C. Oxalyl bromide (4 mL, 2M in DCM, 24 mmol) was added dropwise over a 5 min period . The reaction was stirred at RT. After a 40 min period, t.l.c. (petrol:ethyl acetate, 2:1) indicated the formation of a major product (Rf 0.7). The reaction was cooled to 0° C. and quenched with ice cold water (30 mL) added over a 5 min period. The reaction was partitioned between DCM (20 mL) and water. The aqueous layer was re-extracted with DCM (3×20 mL), the combined organic layers were washed with brine (40 mL), dried (MgSO4), filtered and concentrated in vacuo to afford the title product (1.10 g, 95%) as a crude yellow oil; δH (400 MHz, CDCl3), 3.57 (1H, dd, J1,2 3.5 Hz, J2,3 9.1 Hz, H-2), 3.68 (1H, dd, J5,6 2.1 Hz, J6,6′ 11.0 Hz, H-6), 3.79-3.84 (2H, m, H-4, H-6′), 4.07 (1H, at, J9.1 Hz, H-3), 4.07-4.11 (1H, m, H-5), 4.47-4.62 (3H, m, PhCH2), 4.74 (s, 2H, PhCH2), 4.84-4.89 (2H, m, PhCH2), 5.10 (1H, d, J11.1 Hz, PhCH2), 6.46 (1H, d, H-1), 7.15-7.41 (20H, m, Ar—H).

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