[2+2+1+1] Cycloaddition for de novo Synthesis of Densely Functionalized Phenols

A unique benzannulation strategy for regioselective de novo synthesis of densely functionalized phenols is described. Through metal-mediated formal [2+2+1+1] cycloaddition of two different alkynes and two molecules of CO, a series of densely functionalized phenols were obtained. The benzannulation strategy allows efficient regioselective installation up to five different substituents on a phenol ring. The resulting phenols have a substitution pattern different from those obtained from Dötz and Danheiser benzannulations.

Palladium-Catalyzed Oxidative Cyclization of α-Allenols in the Presence of TBN: Access to 3(2H)-Furanones

A new palladium-catalyzed oxidative cyclization of α-allenols is described. The readily accessible α-allenols participate in intra-molecular oxidative cyclization in the presence of TBN to grant access to multisubstituted 3(2H)-furanones, which are common motifs in several biologically important natural products and pharmaceuticals.

Total Syntheses of Chloropupukeananin and Its Related Natural Products

Chloropupukeananin is a natural product that inhibits HIV-1 replication and has antitumor activity. Its structure consists of a chlorinated tricyclo[4.3.1.03,7]decane core skeleton with an array of highly oxidized multifunctional groups. In the biosynthesis of chloropupukeananin, (+)-iso-A82775C and (−)-maldoxin are employed as biosynthetic precursors for the intermolecular Diels–Alder and carbonyl–ene reactions, followed by the migration of the p-orcellinate group. Chloropupukeanolides and chloropestolides are intermediates and isomers in biosynthesis; their unique chemical structures and biosynthetic pathways have attracted significant attention from synthetic chemists. In this review, I present the synthetic studies on chloropupukeananin and its related compounds that have been conducted thus far.

Biomimetic Total Syntheses of (+)-Chloropupukeananin, (-)-Chloropupukeanolide D, and Chloropestolides

Chloropupukeananin, chloropupukeanolides, and chloropestolides are a family of structurally complex bioactive natural products that possess highly functionalized tricyclo[4.3.1.0^3,7]decane or bicyclo[2.2.2]octane skeletons. Biosynthesis of the chloropupukeananin family is triggered by the intermolecular heterodimeric Diels-Alder reaction between maldoxin and iso-A82775C; however, the enzymes involved have not yet been identified. We herein report the one-pot biomimetic synthesis of chloropupukeananin and chloropupukeanolide D. Moreover, the effect of the solvent on the intermolecular Diels-Alder reaction of siccayne and maldoxin suggested that the biosynthesis of the chloropupukeananin family involves a Diels-Alderase-catalyzed heterodimeric Diels-Alder reaction.

Enantioselective synthesis of chiral 3-alkyl-3-nitro-4-chromanones via chiral thiourea-catalysed intramolecular Michael-type cyclization

Herein we report an enantioselective method for the rapid construction of chiral 3-nitro-4-chromanones via a chiral thiourea-catalyzed intramolecular Michael-type cyclization reaction. With this method, a series of 3,3-disubstituted-3-nitro-4-chromanones bearing contiguous C2/C3 stereocenters were obtained with high diastereoselectivities and good to excellent enantioselectivities. In vitro biological evaluations indicated that the chiral amide derivative of the product showed more potent antitumor activities than both the racemic and the corresponding enantiomers, showcasing the high influence of enantioselective methodology development toward medicinal studies.