Pyridine → 7-beta-D-galactopyranosyloxy coumarin-4-acetic acid-(2-methoxy ethyl) amide

Participants

Reaction Steps

10 mg (0.026 mmoles) of 7-β-D-galactopyranosyloxycoumarin-4-acetic acid (i.e. compound 4 prepared as described in Scheme i) was dissolved in 1.6 ml of dry anhydrous DMF under nitrogen. Pyridine (0.075 ml, 0.92 mmoles) was added dropwise followed by the addition of pentafluorophenyltrifloroacetate (0.1 ml, 0.58 mmoles). The progress of the reaction was followed on a TLC plate by eluting with a mixture of i-PrOH/EtOH/NH4OH/water (60/35/5/20). The Rf of starting material (acid) was 0.4; and the Rf of the reactive intermediate was 0.533. The TLC plate was visualized by spraying a mixture of (anisaldehyde/H2SO4 /EtOH/CH3COOH in the ratio 1/1/18/2 drops) and heating on a hot plate. After the formation of the intermediate (3 hrs), 3-methoxy ethylamine (0.1 ml, 0.8 mmoles) was added dropwise and left to stir at room temperature under N2 for 12 hrs. The formation of the product was confirmed on TLC and the Rf of amide product was 0.41. The DMF was evaporated on a rotary evaporator under vacuum at 40-45° C. After evaporating to dryness the residue was dissolved in I ml of 50/50 CH3CN/water. The crude material was purified on a C-8 preparatory HPLC column using a gradient of 5/95 CH3CN/water (0.1% TFA) to 30/70 CH3CN/water (0.1% TFA) in 25.5 min. The peak eluting at 16 min was collected and the solvent lyophilized and the yield was 54%. The structure of the product was confirmed by 1H-NMR (CD3)2SO:δ 3.12 (t, 2H, CH2 --CH2 --OCH3), 3.32 (m, 5H, HN--CH2 --CH2 --CH3, CH2 --OCH3), 3.36-3.66 (m, 6H, H-2,3,4,5,6,6), 4.99 (d, 1H, J1,2 7.8 Hz), J1,2 of 7,8 Hz confirms β-configuration., 4.52, 4.54, 4.8, 5.45 (d,t,d,d, 1H, 1H, 1H, 1H, 2--OH, 3--OH, 4--OH, 6--OH), 6.38 (s, 1H, H-3), 7.0 (dd, 1H, H-6), 7.15 (d, 1H, H-8), 7.7 (d, 1H, H-5). MS: Mol. Formula. C20H25NO10. Calcd. 439.21, observed (M+Na)+ 462.0. Solubility in 0.1 mM Tris, 0.1 mM KCl pH 8.33: 1.5 mg/ml.

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