Highly enantioselective Diels–Alder reaction of Danishefsky-type diene and electron-deficient olefins catalyzed by an Yb(III)/chiral bis-urea complex

[Catalytic Synthesis of Optically Active Polycyclic Heterocyclic Compounds]

In basic pharmaceutical sciences to achieve drug development, research on the efficient chemical synthesis of small molecules having cyclic skeletons is important. We have been engaged in the development of artificial catalysts for asymmetric ring formation reactions that exclusively synthesize right-handed or left-handed cyclic compounds and have achieved the construction of optically active cyclic skeletons using our original catalysts. The synthesis of biologically active compounds was facilitated through six-membered ring construction by Diels-Alder reaction of Danishefsky diene; however, no asymmetric variant of the reaction has been achieved. We approached this unresolved issue using multi-coordinated lanthanide metals. A new chiral lanthanide catalyst was developed, and the catalytic asymmetric Diels-Alder reaction of Danishefsky diene was realized for the first time. By modifying the chemical structure of Danishefsky diene, we applied the lanthanide catalyst to the syntheses of polycyclic compounds and biologically active compounds. We achieved the asymmetric synthesis of natural products, antibacterial and antimalarial compounds, and an anti-obesity drug lead compound. Moreover, the novel catalyst exhibited higher performance than the previously reported ones. The latest generation of the catalyst can be handled stably in air at room temperature. Furthermore, we succeeded in the development of new catalysts by focusing on the properties of its metal precursors, such as nickel and indium, and achieved the construction of polycyclic skeletons by using these catalysts.

Optically Active Helical Lanthanide Complexes: Storable Chiral Lewis Acidic Catalysts for Enantioselective Diels-Alder Reaction of Siloxydienes

Lanthanide triflates and a series of hexadentate chiral ligand complexes were synthesized. X-ray-quality crystals were obtained from mixtures of the lanthanide complexes, which were helical in shape. The complexes showed Lewis acidity and catalyzed the enantioselective Diels-Alder reaction of electron-rich siloxydienes. The complexes were stable enough to be stored at ambient temperature on a laboratory bench and retained their Lewis acidity even after a month.

Catalytic Enantioselective Total Synthesis of the Picrotoxane Alkaloids (-)-Dendrobine, (-)-Mubironine B, and (-)-Dendroxine

A concise enantioselective total synthesis of three sesquiterpenoid alkaloids-(-)-dendrobine, (-)-mubironine B, and (-)-dendroxine-is presented, which highlights the state-of-art catalytic methods, including enantioselective Diels-Alder cycloaddition, iron-catalyzed aerobic lactonization, copper-catalyzed cycloisomerization, and free-radical-initiated hydroazidation.

Construction of Optically Active Isotwistanes and Aminocyclitols Using Chiral Cyclohexadiene as a Common Intermediate

We have developed a new method for synthesizing chiral isotwistane and homoisotwistane skeletons as well as aminocyclitols in a highly stereoselective manner. These results were achieved through the use of a common intermediate, which was derived from the ytterbium-catalyzed asymmetric Diels-Alder reaction of Danishefsky diene.

Catalytic enantioselective total synthesis of (-)-platyphyllide and its structural revision

The catalytic asymmetric total synthesis of platyphyllide has been accomplished. A key highly substituted cyclohexene derivative has been obtained by the catalytic asymmetric Diels-Alder reaction of Danishefsky diene with an electron-deficient alkene. The Diels-Alder adduct was converted to a protected cyclohexane-1,3-dione in chiral form by catalytic Ito-Saegusa oxidation. Although the reported structure of platyphyllide was successfully synthesized, the optical rotation was opposite that of the natural compound. The absolute configuration of natural (-)-platyphyllide is revised to be a (6S,7S)-enantiomer.