C([O:8][CH2:9][C:10]([O:12][C:13]1[CH:22]=[C:21]2[C:16]([C:17](=[O:41])[C:18]([C:23]3[CH:28]=[CH:27][C:26]([O:29][C:30](=[O:40])[CH2:31][O:32]CC4C=CC=CC=4)=[CH:25][CH:24]=3)=[CH:19][O:20]2)=[CH:15][CH:14]=1)=[O:11])C1C=CC=CC=1>C(OCC)(=O)C.[Pd]>[OH:8][CH2:9][C:10]([O:12][C:13]1[CH:22]=[C:21]2[C:16]([C:17](=[O:41])[C:18]([C:23]3[CH:28]=[CH:27][C:26]([O:29][C:30](=[O:40])[CH2:31][OH:32])=[CH:25][CH:24]=3)=[CH:19][O:20]2)=[CH:15][CH:14]=1)=[O:11]Benzyloxy-acetic acid 4-[7-(2-benzyloxy-acetoxy)-4-oxo-4H-chromen-3-yl]-phenyl ester 42 (1 gram, 1.82 mmol) is dissolved in ethyl acetate (50 ml) in a pressure vessel, Palladium on carbon (5%, 0.5 gram) added and the mixture stirred under an atmosphere of hydrogen (4 Kg) for 22 hours. The catalyst is removed by filtration, ethyl acetate distilled under vacuum. The crude 43 can be purified by column chromatography on silica gel using benzene:ethyl acetate (8:2) as eluant to get the desired product.
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