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Stereoselective Synthesis of the Decahydroquinoline Alkaloid cis-195J

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journal contribution
posted on 05.08.2021, 18:33 by Rudina Veliu, Christoph Schneider
The first enantioselective synthesis of two C-5 diastereomers of the proposed structure of the decahydroquinoline alkaloid cis-195J has been achieved. The key step of our strategy is the highly stereoselective vinylogous Mukaiyama–Mannich reaction (VMMR), which gave rise to the first two stereogenic centers at the ring fusion with excellent diastereo- and enantiocontrol. Through alkyne cyclization and enamine reduction the correct cis-configuration between C-2, C-4a, and C-8a in the decahydroquinoline backbone was established. Subsequently, a radical cyclization of a tethered alkyl iodide onto the enoate assembled the bicyclic cis-decahydroquinoline as a mixture of two C-5 diastereomers. Further elaboration of the C-5 side chain eventually provided both diastereomers of cis-195J, which were readily separated, and their constitution and configuration were thus unambiguously proven for the first time.