A Short Synthesis of Natural Isocoumarin Glucoside Delphoside

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.

A Short Synthesis of Natural Isocoumarin Glucoside Delphoside

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 .