Wenkert s enamine

Aza-annulation of 104 with a variety of acrylate reagents has been utilized in the synthesis of indoloquinoiizidine alkaloid skeletons (eq. 25). Aza-annulation of 104 was affected with acrylic acid (91%), acrylic acid/DPPA (95%), acryloyl chloride/DMAP (64, 63%), and methyl acrylate (37, 52%) to generate the pentacyclic eburnane skeleton 105.42 Carbonyl reduction gave Wenkert s enamine (106), which was carried on in the synthesis of ( )-apovincamine (107) and the clinically active synthetic analog ( )-Cavinton (108).42... 

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