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Eight‐Step Enantioselective Total Synthesis of (−)‐Cycloclavine
Abstract:The first enantioselective total synthesis of (?)‐cycloclavine was accomplished in 8 steps and 7.1 % overall yield. Key features include the first catalytic asymmetric cyclopropanation of allene, mediated by the dirhodium catalyst Rh2(S‐TBPTTL)4, and the enone 1,2‐addition of a new TEMPO carbamate methyl carbanion. An intramolecular strain‐promoted Diels–Alder methylenecyclopropane (IMDAMC) reaction provided a pivotal tricyclic enone intermediate with more than 99 % ee after crystallization. The synthesis of (?)‐ 1 was completed by a late‐stage intramolecular Diels–Alder furan (IMDAF) cycloaddition to install the indole.
Keywords:Allen  Clavin-Alkaloide  Cycloadditionen  Cyclopropanierungen  Enantioselektivitä  t
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