An efficient approach for the synthesis of biologically interesting fused tetracyclic isoquinolines in high yields and with a broad substrate scope has been developed. The strategy features an AgNO(3) catalyzed 'one-pot' cascade process involving formation of two new C-N bonds and one new C-O bond.

The synthesis of a functionalized, tetracyclic core of N-methylwelwitindolinone C isothiocyanate is reported. The approach features a convergent coupling between an indole iminium ion and a highly functionalized vinylogous silyl ketene acetal followed by an intramolecular palladium-catalyzed cyclization that proceeds via an enolate arylation.

The first total synthesis of the tetracyclic alkaloid (-)-acutumine is described. Key reactions include an asymmetric ketone allylation mediated by Nakamura's chiral allylzinc reagent, an anionic oxy-Cope rearrangement, and the Lewis acid-promoted cyclization of an amine onto an alpha,beta-unsaturated dimethyl ketal.

Various readily available, Ugi-derived dehydroalanines were used as pivotal templates to easily and efficiently assemble diverse pharmacologically important polyheterocyclic systems through cascade palladium-catalyzed C-C bond formation processes. Allyl, homoallyl and propargylamine led to the formation of benzopyrrolizidinones, benzoindolizidinones and pyrazinoisoquinolines, respectively, whil...

A range of new biphenylazepinium salt organocatalysts effective for asymmetric epoxidation has been developed incorporating an additional substituted oxazolidine ring, and providing improved enantiocontrol in alkene epoxidation over the parent structure. Starting from enantiomerically pure aminoalcohols, tetracyclic iminium salts were obtained as single diastereoisomers through an atroposelecti...

Herein, we describe the synthesis of new functionalized tricyclic and tetracyclic indole derivatives via samarium diiodide induced ketyl cyclizations. The intermediate samarium organyls were either protonated using different proton sources or alkylated with various electrophiles in a highly diastereoselective manner. The obtained products were subjected to further transformations leading to syn...

FeCl3- and FeBr3-mediated tandem carboarylation/cyclization of propargylanilines with diethyl benzaldehyde acetals furnished the tetracyclic core of indeno[2,1-c]quinolines. 5-Tosyl-6,7-dihydro-5H-indeno[2,1-c]quinoline and 7H-indeno[2,1-c]quinoline derivatives were obtained in good to excellent yields, respectively, by tuning the FeX3 loadings and/or reaction temperatures.

The ubiquitous ketone carbonyl group generally deactivates substrates toward radical-based fluorinations, especially sites closest to it. Herein, ketones are used instead to direct aliphatic fluorination using Selectfluor, catalytic benzil, and visible light. Selective band g-fluorination are demonstrated on rigid mono-, di-, tri-, and tetracyclic (steroidal) substrates employing both cyclic an...

The first enantioselective total syntheses of virosaine A and bubbialidine are described. Key transformations include the formation of a tetracyclic intermediate via an intramolecular aza-Michael addition, generation of a N-hydroxy-pyrrolidine through a Cope elimination and an intramolecular [1,3]-dipolar cycloaddition to generate a complex 7-oxa-1-azabicyclo[3.2.1]octane ring system.

This paper describes a formal total synthesis of the marine ladder toxin hemibrevetoxin B from Danishefsky's dienes. This approach couples the generation of C-glycosides from cyclic enol ethers with metathesis or acid-mediated annulation reactions. The result is a highly efficient synthesis of the tetracyclic ring system of hemibrevetoxin B.