(-)-Daphnilongeranin B and (-)-daphenylline are two hexacyclic Daphniphyllum alkaloids, each containing a complex cagelike backbone. Described herein are the first asymmetric total synthesis of (-)-daphnilongeranin B and a bioinspired synthesis of (-)-daphenylline with an unusual E ring embedded in a cagelike framework. The key features include an intermolecular [3+2] cycloaddition, a late-stage aldol cyclization to install the F ring of daphnilongeranin B, and a bioinspired cationic rearrangement leading to the tetrasubstituted benzene ring of daphenylline.

An efficient strategy for the one-pot synthesis of polysubstituted pyridines via a cascade reaction from aldehydes, phosphorus ylides, and propargyl azide is reported. The reaction sequence involves a Wittig reaction, a Staudinger reaction, an aza-Wittig reaction, a 6π-3-azatriene electrocyclization, and a 1,3-H shift. This protocol provides quick access to the polysubstituted pyridines from readily available substrates in good to excellent yields.

Thermal treatment of indenyl-functionalized imidazolium salts and N-heterocyclic carbenes with Ru3(CO)12 gave different products. The normal mononuclear metal complexes (2a, 2b) were obtained via direct reaction of indenyl-functionalized imidazolium salts (1a, 1b) with Ru3(CO)12. Unexpected intramolecular C-H activated products (3a, 3b, 4a, 4b) were obtained via thermal treatment of corresponding indenyl-functionalized N-heterocyclic carbenes. All complexes were determined by 1H NMR, 13C NMR, IR spectra and elemental analysis. The molecular structures of 2b, 3a, 3b and 4b were determined by X-ray diffraction.

Described herein is the first asymmetric total synthesis of (+)-harringtonolide, a natural diterpenoid with an unusual tropone imbedded in a cagelike framework. The key transformations include an intramolecular Diels-Alder reaction and a rhodium-complex-catalyzed intramolecular [3+2] cycloaddition to install the tetracyclic core as well as a highly efficient tropone formation.

Bin Cheng (程彬) ‡1 , Yiwei Meng (孟艺伟) ‡1 , Yanbing Cui (崔延冰) ‡ , Chunfang Li (李春芳) ‡ , Fei Tao (陶飞) § , Huijia Yin (殷会佳) ‡ , Chunyu Yang (杨春玉) ‡2 , and Ping Xu (许平) ‡ §