The total synthesis of (±)-sanggenol F

Asymmetric catalytic [1,3]- or [3,3]-sigmatropic rearrangement of 3-allyloxy-4H-chromenones and their analogues

“… 9 Substituted 3-hydroxyl pyranones and benzopyranones are popular structural motifs in natural products, such as flavonol, lawsone, kojic acid, and allomaltol ( Scheme 1b ). Rearrangements of 3-allyloxyflavone or O -allyl kojic acid have been designed for the synthesis of sanggenon-type natural products by Porco 10 and Hou, 11 and the tricyclic core of 1α-alkyldaphnanes by Wender and co-workers. 12 There are rare examples related to the asymmetric catalytic C2-functionalization of 3-hydroxychromenones: one is a chiral Pybox-Sc( iii )-complex-catalyzed formal [3,3]-rearrangement to construct 3,4-chromanediones by Porco and co-workers, 13 and another is the chiral NHC-initiated formation of an α,β-unsaturated acyl azolium intermediate to perform Coates–Claisen rearrangement by Bode's group 14 and Rafiński's group.…”

Total Synthesis of Kuwanons A and B and Discovery of Their Antibacterial Mechanism

“…Coupling of 10 with 11 in the presence of EDCI/DMAP gave ester 12 in a 93% yield. , Subsequently, the NaH-promoted Bk-Vk rearrangement of 12 gave β-diketone 13 , which was alkylated with 1-bromo-3-methyl-2-butene ( 14 ) to generate intermediate 15 in 71% yield over two steps . However, the following cyclization of 15 under the reported conditions, including H 2 SO 4 /AcOH, − H 2 SO 4 /EtOH, CuCl 2 /TMSCl, and camphorsulfonic acid (CSA), only resulted in complex mixtures and no desired cyclic product could be obtained. We attributed our failure to the instabilities of the MOM groups and the isopentenyl group in those strongly acidic conditions; thus compound 15 was stirred in a weak acid media (AcONa/AcOH) at 100 °C to give the cyclic product 16 successfully. − , It should be noted that the C-5 MOM was simultaneously removed during the cyclization process.…”

Multigram, Chromatography-Free Synthesis of the Flavonol Morin

“…25 In addition, we identified ethyl ester 24 and phenolic products 23 and 25. 26,27 2,4-Dimethoxyphenol (25) may have been formed by the Dakin reaction of 2,4-dimethoxybenzaldehyde (9). For the formation of 9 itself, intermediacy of a chalcone epoxide has been proposed.…”

“…Hou and coworkers employed methylated intermediates in their Baker− Venkataraman synthesis. 9 Starting material 2 was O-methylated twice, before being acylated with 2,4-dimethoxybenzoyl chloride. After six further steps, morin (1) was obtained in 24% yield on a 100 mg scale.…”

“…Remarkably, the synthesis did not require protection of any of the phenolic hydroxy groups. Hou and coworkers employed methylated intermediates in their Baker–Venkataraman synthesis . Starting material 2 was O-methylated twice, before being acylated with 2,4-dimethoxybenzoyl chloride.…”