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Stereoselective Synthesis of (3R)-3,4-Dihydro-6,8-dimethoxy-3-undecyl- 1H-[2]benzopyran-1-one and Derivatives, Metabolites from Ononis natrix

✍ Scribed by Aamer Saeed

Publisher: John Wiley and Sons
Year: 2003
Tongue: German
Weight: 124 KB
Volume: 86
Category: Article
ISSN: 0018-019X
DOI: 10.1002/hlca.200390038

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✦ Synopsis

Abstract

A short stereoselective synthesis of (3__R__)‐3,4‐dihydro‐6,8‐dimethoxy‐3‐undecyl‐1__H__‐[2]benzopyran‐1‐one and derivatives isolated from Ononis natrix has been described. Condensation of dodecanoyl chloride with 3,5‐dimethoxyhomophthalic acid afforded 6,8‐dimethoxy‐3‐undecylisocoumarin 3, which, on sequential saponification and esterification, yielded the keto ester 5. Enantioselective reduction of 5 with TarB‐NO~2~/LiBH~4~ directly furnished the title dihydroisocoumarin 1a in 80% ee (82% yield). Partial as well as complete demethylation of the latter provided the dihydroisocoumarins 1b and 1c, respectively. Diastereotopy of the CH~2~ H‐atoms on either side of the stereogenic center (C(3)) and the mass‐fragmentation pattern of the dihydroisocoumarins have also been described. All of the compounds synthesized were examined in vitro for antifungal activity.

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