Nitraria alkaloids synthesis

Park et al. also reported an analogous strategy for the synthesis of (+)-isonitramine (107) [61], A phase-transfer catalyzed enantioselective ot-alkylation of lactam 108, followed by subsequent manipulations, was employed for the successful total synthesis of the Nitraria alkaloid (+)-isonitramine (107) (Scheme 21). 

Synthesis of (—)-Sibirine. Various types of alkaloids have been prepared by conjugate addition of carbon-centered radicals to unsaturated sulfones. This approach is used in the stereoselective synthesis of the Nitraria spirocyclic alkaloid (—)-sibirine, where a 6-exo-trig radical cyclization to an a,(3-unsaturated sulfone leads to the spirocyclic skeleton of the natural product (Eq. 153).263 The y-nitrogen-functionalized sulfone so obtained is then desulfonylated under dissolving-metal conditions. 

Plants of the Nitraria genus have yielded a large number of structurally unusual alkaloids [77]. Poupon has reported a very straightforward biomimetic synthesis of one of these compounds, tangutorine, that starts from compound 98, readily available from a double aldol reaction between two molecules of glutaraldehyde. Treatment of 98 with tryptamine under mildly acidic conditions directly afforded compound 100 via a Michael/Pictet-Spengler domino process, and a final reduction step afforded tangutorine 101 (Scheme 3.31) [78]. 

For a review of the chemistry of these alkaloids, see GraveL E., Poupon, E. (2010). Biosynthesis and hiomimetic synthesis of alkaloids isolated from plants of the Nitraria and Myriotieuwn genera an unusual lysine-based metaboUsm. Natural Product Reports, 27, 32-56. 

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