Biomimetic manzamine alkaloids

For the structurally more complex molecule 18, only the Schrock conditions worked. Compound 18 has been synthesized as a synthetic precursor of the marine alkaloid nakado-marin A (19 [14]) from the marine sponge Amphimedon sp. Nakadomarin A (19) belongs to the manzamine alkaloids, which are also targets of biomimetic syntheses [15], For both strategies, there is still some distance to go. 

As part of a biomimetic approach to the synthesis of the manzamine alkaloids, Baldwin et al. found that treatment of model compound 120 in pH buffer 8.3 for 18 h followed by reduction with excess sodium borohydride gave the adduct 121 in low yield (Figure 3.5) [71]. 

A model reaction carried out by Baldwin and coworkers as part of a biomimetic synthesis of the manzamine alkaloids [71]. This reaction generates the tricyclic core of the ingenamine... 

Further insights into the biosynthesis of manzamines came from the synthetic studies made on the conversion of 3-alkyl-dihydropyridinium salts to the unstable 3-alkyldihydropyridine reported in Fig.(24) [39]. Similar compounds were used in model studies towards a biomimetic synthesis of the alkaloids keramaphidin A and halicyclamine A [40]. 

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