Enantioselective Total Syntheses of (R)- and (S)-Naphthotectone, and Stereochemical Assignment of the Natural Product
2016
Guerrero-Vásquez, Guillermo A. | D. Galarza, Flávia A. | Kleber Z. Andrade, Carlos | González Molinillo, José María | Macías Domínguez, Francisco Antonio | Química Orgánica
Both isomers of naphthotectone, an isoprenoid quinone from Verbenaceae Tectona grandis possessing interesting biological activities, were enantioselectively obtained by two different synthetic routes in which the carbon side-chain of the naphthoquinone core was introduced using either a Sonogashira or a Heck coupling reaction. In both cases, the naphthoquinone core of the final products was obtained by a late-stage anodic treatment. (R)-Naphthotectone was obtained in six steps from leuconaphthazarin with an overall yield of 38 % and an enantiomeric excess of 86 %. This compound was found to have the same absolute configuration as the natural product at its C-3′ stereogenic center. (S)-Naphthotectone was obtained in five steps from leuconaphthazarin with an overall yield of 36 % and an enantiomeric excess of 80 %.
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