Inter- and Intramolecular Hetero-Diels-Alder Reactions; Part 50: Domino Reactions in Organic Chemistry: The Knoevenagel-hetero-Diels-Alder-Hydrogenation Sequence for the Biomimetic Synthesis of Indole Alkaloids via Strictosidine Analogues

All articles of this category A new biomimetic access to indole alkaloid derivatives via strictosidine analogues is described using a highly efficient and selective domino reaction consisting of a tandem Knoevenagel-hetero-Diels-Alder-hydrogenation sequence. In a three component reaction of the aldehyde 27f , the 1,3-dicarbonyl compound 28 and the enol ether 30a a 1 : 1-mixture of 31c and 31d is obtained in 91% yield which after hydrogenation gives the indole alkaloid derivative 35a belonging to the pseudo series as a single compound. Similarly, reaction of 27f , 28 and 30b also affords 35a after hydrogenation as the only compound. In the domino reaction of 27e , 28 and 30a the indole alkaloid derivative 36b of the normal type is formed in 46% yield.