Synthesis of 6-O-methyl ether of Scorzocreticin and Scorzocreticoside I, metabolites from Sorzonera cretica.
6-O-methyl ether of racemic scorzocreticin (1a) and its 8-O-beta-D-glucoside, scorzocreticoside I (1b), isolated from Greek endemic species Scorzonera cretica have been synthesized. 6,8-Dimethoxy-3-(4-methoxyphenyl)isocoumarin (3) was obtained by reaction of 3,5-dimethoxyhomophthalic acid (2) with 4-methoxy-benzoyl chloride at elevated temperature. Hydrolysis of isocoumarin (3) to keto acid (4) followed reduction and spontaneous cyclodehydration to afford ( +/- )-6,8-dimethoxy-3-(4-methoxyphenyl)-3,4-dihydroisocoumarin (5) which was regioselectively demethylated to ( +/- )-6-O-methylscorzocreticin (6). Glycosylation of the latter using 2,3,4,6-tetra-O-acetyl-alpha-D-glucopyranosyl bromide in the presence of silver carbonate in quinoline under Koenigs-Knorr conditions afforded 6-methoxy-8-O-glucoside tetraacetate (7) as a 1:1 diastereomeric mixture. Finally, deacetylation of (7) using sodium methoxide afforded the diastereomeric mixture of R and S 6-O-methylscorzocreticin 8-O-glucosides (8). The 6-O-methyl ether of natural scorzocreticoside I (1b) was separated and identified on the basis of sign of optical rotation.
Saeed
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Department of Chemistry, Quaid-I-Azam University, Islamabad, 45320, Pakistan. aamersaeed@yahoo.com
D019659:Asteraceae; D003374:Coumarins / Q000737:chemistry*; D006027:Glycosides / Q000737:chemistry*; D006801:Humans; D049934:Isocoumarins / Q000737:chemistry*; D008738:Methyl Ethers / Q000138:chemical synthesis; D008517:Phytotherapy; D010936:Plant Extracts / Q000737:chemistry*
D003374:Coumarins; D006027:Glycosides; D049934:Isocoumarins; D008738:Methyl Ethers; D010936:Plant Extracts; C446581:scorzocreticin; C446582:scorzocreticoside I