A simple synthesis of delphoside, 3-methyl-6-hydroxy-8-O-β-D-glucopyranosyloxy isocoumarin (1), isolated from Delphinium spp. is described. 3,5-Dimethoxyhomophthalic anhydride (2) on treatment with acetyl chloride in the presence of 1,1,3,3-tetramethylguanidine (TMG) and triethyl amine afforded the 6,8-dimethoxy-3-methylisocoumarin (3). Regioselective demethylation of the latter furnished 8-hydroxy-6-methoxy-3-methylisocoumarin (4). Glycosylation with O-(2,3,4,6-tetra-O-acetyl-D-glucopyranosyl)trichloroacetimidate in presence of catalytic amount of boron trifluoride etherate followed by deacetylation using 5% potassium carbonate afforded 3-methyl-6-methoxy-8-O-β-D-glucopyranosyloxyisocoumarin (6) that was finally demethylated to yield delphoside 1.
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