Stereoselective Synthesis of the Decahydroquinoline Alkaloid -.

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.