Synthesis of 6-O-methyl ether of Scorzocreticin and Scorzocreticoside I, metabolites from Sorzonera cretica
Title:
Synthesis of 6-O-methyl ether of Scorzocreticin and Scorzocreticoside I, metabolites from Sorzonera cretica
Author:
Saeed, A.
Appeared in:
Journal of Asian natural products research
Paging:
Volume 8 (2006) nr. 5 pages 417-423
Year:
2006-07
Contents:
6-O-methyl ether of racemic scorzocreticin (1a) and its 8-O-β-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-α-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.
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