electron-deficient olefins gave substituted hydrocarbazoles in up to 99% yield and 94% ee. This reaction was catalyzed by a novel chiral holmium(III) complex. Alkylation of the cycloadduct gave a tricyclic compound with four continuous chiral centers, one of which was a quaternarycarbon.
Catalytic Enantioselective Total Synthesis of the Picrotoxane Alkaloids (−)-Dendrobine, (−)-Mubironine B, and (−)-Dendroxine
作者:Lei Guo、Wolfgang Frey、Bernd Plietker
DOI:10.1021/acs.orglett.8b01782
日期:2018.7.20
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.
The synthesis and utility of the novel axially chiral bis-urea ligand BINUREA are described. A complex of this urea ligand with ytterbium triflate and DBU can be used in the catalytic enantioselectiveDiels–Alder reaction of Danishefsky-type diene and electron-deficient olefins to give the adducts in good to excellent yield and enantiomeric excess (ee).