The first enantioselective synthesis of two C-5 diastereomers of the proposed structure of the decahydroquinoline alkaloid - 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 -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 -decahydroquinoline as a mixture of two C-5 diastereomers. Further elaboration of the C-5 side chain eventually provided both diastereomers of -, which were readily separated, and their constitution and configuration were thus unambiguously proven for the first time.
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Article Synopsis
- The first asymmetric total synthesis of the alkaloid senepodine F has been successfully completed, featuring a unique structure with both decahydroquinoline and quinolizidine rings.
- Key steps in this process included an organocatalytic asymmetric Diels-Alder reaction, a diastereoselective intramolecular -Michael reaction, and an S2 cyclization that helped to create complex nitrogen-containing compounds.
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