Total Synthesis of (−)-Magnoshinin and (+)-Merrilliaquinone

Total Synthesis of (−)-Magnoshinin and (+)-Merrilliaquinone

Author: European Journal of Organic Chemistry

Merrilliaquinone (pictured left) is a rare natural product with a dihydronaphthoquinone scaffold. It was isolated in racemic form from the plant Illicium merrillianum. The selective cytotoxicity of (+)-merrilliaquinone towards human hepatoma cells over the normal liver cells makes it a potential lead for anti-cancer drug development.

Magnoshinin (pictured right) is a natural product with a dihydronaphthalene scaffold and shows anti-inflammatory activity. It was isolated from the plant Magnolia salicifolia. Magnoshinin could be a possible biosynthetic precursor for merrilliaquinone.

On the basis of this hypothesis, Tabrez Khan, Indian Institution of Technology Bhubaneswar, Khurdha, India, and colleagues have developed a unified approach for the first asymmetric total syntheses of (−)-magnoshinin and (+)-merrilliaquinone. The team first prepared the chiral tetralin core, starting from 3-(2,4,5-trimethoxyphenyl)propanoic acid and using a relayed asymmetric induction strategy.

The researchers then used a chemoselective, late-stage oxidative functionalization protocol employing 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) to obtain (−)-magnoshinin, which can be converted to (+)-merrilliaquinone via an oxidative demethylation. These two products were obtained in overall yields of 28.2 % and 20.6 %, respectively.



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