| 50% |
With hydrogen;palladium(II) hydroxide/carbon; In tetrahydrofuran; methanol; water; for 2h; |
To a solution of the benzylated dimer (700 mg) in tetrahydrofuran [(THF)] (30 ml) were added methanol [(MEOH)] (30 [ML),] water [(1.] 5 ml) and palladium hydroxide on carbon (Pd (OH) 2/C) (20%, containing up to 50% H20, 300 mg). The mixture was shaken under an atmosphere of hydrogen for 2 hours, filtered through ceelite, which was washed with methanol. HPLC analysis (Figure 9) of the dried product, showed it to contain about [80%] of the procyanidin dimer B2 at 10.3 minutes, together with small amounts of epicatechin at 12.4 minutes, and the procyanidin trimer Cl at 17.6 minutes, all identical with pure samples. Final purification of the product was accomplished by column chromatography over Sephadex LH20 when 95% ethanol eluted the procyanidin dimer B2 in fractions 45 to 56 (140 mg, 50% yield). The purified procyanidin B2 is observed at 10.3 minutes in the HPLC tracing of Figure 10. [1H-NMR] (CD3) 2CO : 2. 83 [(1H,] d, J17), 2.96 [(1H,] dd, J5,17), 3.76 [(1H,] m, OH), 3.83 [(1H,] m, OH), 4.10 [(1H,] d, J5), 4.41 [(1H,] [BR S),] 4.83 [(1H,] s), 5.07 [(1H,] [BR S),] 5.20 (1H, br s), 6.07 [(1H,] [S),,] 6.09 [(1H,] s), 6.11 [(1H,] s), 6.83 (3H, s), 7.00 [(1H,] br s), 7.08 [(1H,] s), 7.20 [(1H,] s), 7. 81 [(1H,] s, OH), 7.87 [(1H,] s, [OH),] 7.91 [(LH,] [S,] OH), 8.02 [(1H,] br [S,] OH) and 8.28 (2H, s, OH) (Figure 11). |
| 45% |
With hydrogen;palladium 10% on activated carbon; In methanol; ethyl acetate; under 750.075 Torr; for 6.7h; |
To a solution of the O-benzyl-dimer according to Part E (22.3 mg, 17.2.mumol) in 0.5 mL of ethyl acetate was added sequentially, 2 mL of methanol and 7.2 mg of 10% Pd/C. The mixture was stirred under 1 bar of H2 for 3 hours and filtered over cotton. The filtration residue was washed with methanol and the combined filtrates were evaporated. An NMR spectrum of the crude product indicated the presence of benzylated material. The procedure was therefore repeated, with the amount of catalyst increased to 17.5 mg and the time extended to 3.7 h. The crude polyphenol dimer (9.6 mg) was purified by preparative HPLC (C18 reverse phase column water/methanol (85:15) with addition of 0.5% acetic acid, detection at 265 nm) to provide 4.5 mg (45%) of polyphenol dimer as an amorphous film. 1H NMR (300 MHz, acetone-d.6/D2O 3:1 (v/v), TMS) delta 7.19 (br, 1 H), 7.01 (overlapping s+br, 2 H), 6.86-6.65 (m, 4 H), 6.03 (br, 3 H), 5.10 (br, 1 H), 5.00 (br, 1 H), 4.69 (br, 1 H), 3.97 (s, 1 H), 2.92, 2.76 (br ABq, 2 H, J=17 Hz); MS (MALDI-TOF, DHBA matrix) m/z (M+K+) 616.8; calcd. for C30H26O12K: 617.1; (M+Na+) 600.8; calcd. for C30H26O12Na: 601.1. |
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