Convergent radical-free synthesis of isoflavanquinones: Divergent total synthesis of abruquinones B, E, and P. (25th April 2023)

• Record Type: Journal Article
• Authors: Uchida, Yuichiro; Kang, Bubwoong; Takikawa, Hirosato
• Is Part Of: Tetrahedron. Volume 136(2023)
• Publication Date: 2023-04-25
• Subjects: Flavonoids -- Isoflavenes -- Isoflavans -- Isoflavanquinones -- Claisen rearrangement -- Cascade Reaction; Chemistry, Organic -- Periodicals; 547.005
• DOI: 10.1016/j.tet.2023.133362
• Languages: English
• ISSNs: 0040-4020

Abstract

Abstract: We report divergent total syntheses of isoflavanquinone natural products based on a new convergent synthetic strategy. A 3-chloro-2 H -chromene, prepared by our originally developed Claisen rearrangement–cyclization cascade, was subjected to Suzuki-Miyaura cross coupling with three purposefully protected 2, 5-dibenzyloxyarylboronic acids to afford isoflavenes with B rings as benzyl-protected hydroquinone moieties. The subsequent catalytic hydrogenation afforded isoflavenes, releasing unmasked hydroquinone moieties. Finally, these hydroquinone moieties were oxidized to quinones in the presence of palladium on carbon and air in one-pot to give three isoflavanquinone natural products, abruquinones B, E, and P quantitatively in all cases (their overall yields were 53, 2.7, and 38%, respectively). Our newly developed method enabled the facile total syntheses of natural isoflavanquinones, including the first syntheses of abruquinones E and P. Graphical abstract: Image 1