Sodium Acetate → 1,3,4,6-Tetra-O-acetyl-2-azido-2-deoxy-D-galactopyranose

Participants

Reaction Conditions

Reaction Steps

To a solution of nitrate ester 68 (17.5 g, 46.5 mmol) in 500 mL of glacial acetic acid is added sodium acetate (7.63 g, 93.0 mmol). The solution is stirred at 100° C. for 3 h and then allowed to cool to room temperature. The reaction mixture is diluted with 1000 mL of ice water and extracted with CH2Cl2 (2×200 mL) The organic layers are combined and washed with ice water (2×400 mL), saturated NaHCO3 (400 mL), saturated NaCl (400 mL), dried over Na2SO4, filtered and concentrated. The crude product is crystallized from hexane/EtOAc to give 7.2 g of 2-azido-2-deoxy-1,3,4,6-tetra-O-acetyl-α,β-D-galactopyranose 69 (mixed anomers). The mother liquors from the crystallization are concentrated and purified by flash chromatography (25% EtOAc/hexane) to give an additional 7.0 g of the product (14.2 g, 81.7% in total) as a mixture of anomers: Rf 0.3 (30% EtOAc/hexane); 1H NMR (CDCl3, 270 MHz, mixture of anomers) δ 6.26 (d, J=3.6 Hz, 1 H, H-1α), 5.50 (d, J=8.6 Hz, 1 H, H-1β), 5.42 (d, J=3.0 Hz, 1 H, H-4α), 5.32 (d, J=3.0 Hz, 1 H, H-4β), 5.25 (dd, J=11.2, 3.0 Hz, 1 H, H-3α), 4.85 (dd, J=10.6, 3.3 Hz, 1 H, H-3β), 4.23 (t, J=6.6 Hz, 1 H, H-5α), 3.95-4.10 (m, 5 H, H-6α, H-5β, H-6β), 3.88 (dd, J=11.2, 3.6 Hz, 1 H, H-2α), 3.78 (dd, J=10.9, 8.6 Hz, 1 H, H-2β), 1.90-2.20 (6s, 24 H, OAc).

Provenance & Evidence