Asymmetric Synthesis of the Tricyclooctane Core of Trachylobane Natural Products and Related Terpenoids

Radical Fluorosulfonylation/Double Diels-Alder Sequence to Access Tricyclo[3.2.1.02,7]octanes

A cascade strategy for the rapid construction of tricyclo[3.2.1.02,7]octanes is reported. This one-pot, two-step sequence can be efficiently accomplished by utilizing readily available propargylic alcohols as the starting materials and FSO2Cl as the fluorosulfonyl radical precursor. The FSO2-functionalized tricyclooctane products, bearing multiple reactive sites, are poised for postderivatizations. Based on mechanism studies, a cascade sequence involving radical hydro-fluorosulfonylation, dehydration, and a double Diels-Alder reaction has been proposed.

Enantioselective Total Synthesis of (-)-Spiroxins A, C, and D

Spiroxins A, C, and D are metabolites that have been identified in the marine fungal strain LL-37H248. Their unique polycyclic structures and intriguing biological activities make them attractive targets for the synthetic community. Based on a scalable enantioselective epoxidation of 5-substituted naphthoquinone, an oxidation/spiroketalization cascade, ortho-selective chlorination of the phenol unit, and oxime-ester-directed acetoxylation, an enantioselective total synthesis of (-)-spiroxins A and C and the first total synthesis of (-)-spiroxin D have been achieved.

Total Synthesis of (-)-Mitrephorone A Enabled by Stereoselective Nitrile Oxide Cycloaddition and Tetrasubstituted Olefin Synthesis

A highly enantioselective and diastereoselective total synthesis of the diterpenoid (−)-mitrephorone A is presented. Key to the synthesis are stereocontrolled 1,4-semihydrogenation of a 1,3-diene to a tetrasubstituted double bond, enzyme-catalyzed malonate desymmetrization, and highly diastereoselective nitrile oxide cycloaddition. The streamlined strategy is a considerable improvement to those reported earlier in terms of diastereo- and enantioselectivity. For the first time, the combination of modern Pd-cross-coupling with Cr-catalyzed reduction allows for rapid access to tetrasubstituted olefins with full stereocontrol.

Stereoselective Synthesis of Tropanes via a 6π-Electrocyclic Ring-Opening/ Huisgen [3+2]-Cycloaddition Cascade of Monocyclopropanated Heterocycles

The synthesis of tropanes via a microwave-assisted, stereoselective 6π-electrocyclic ring-opening/ Huisgen [3+2]-cycloaddition cascade of cyclopropanated pyrrole and furan derivatives with electron-deficient dipolarophiles is demonstrated. Starting from furans or pyrroles, 8-aza- and 8-oxabicyclo[3.2.1]octanes are accessible in two steps in dia- and enantioselective pure form, being versatile building blocks for the synthesis of pharmaceutically relevant targets, especially for new cocaine analogues bearing various substituents at the C-6/C-7 positions of the tropane ring system. Moreover, the 2-azabicyclo[2.2.2]octane core (isoquinuclidines), being prominently represented in many natural and pharmaceutical products, is accessible via this approach.