Quinolizidine alkaloids bioactivity

The indolizidine and quinolizidine alkaloids covered in this review proved to have relevant bioactivity. 

Alkaloids are produced in nature by some organisms for their physiological purposes. The best known alkaloid producers are plants, but animals and humans also can produce endogenic alkaloids. Moreover, the use of alkaloids by sequestration juice and feed by herbivores and a consumption of storage alkaloids in animal body by carnivores is a process often observed in nature. The problem of narcotism (the use of narcotic bioactive compounds and their consequences) therefore also exists in nature, not only in the human society. It is observed that some insects are narcotized by quinolizidine alkaloids. Some bumblebees can be aggressive to others after visiting alkaloid plants. 

On the other hand, a direct asymmetric Mannich reaction was reported, in 2009, by Rutjes et al. in the course of developing a synthesis of the bioactive quinolizidine alkaloid lasubine II. Therefore, the key step of this synthesis was the L-proline-catalysed Mannich reaction between acetone, para-mtm-benzaldehyde and veratryl aldehyde, providing the expected Mannich adduct in moderate yield and almost complete enantioselectivity (Scheme 3.5). This chiral p-amino ketone was further converted into the desired (-F )-lasubine II. 

The allylboronate reagent 1 was used twice in the synthesis of (-)-lasubine I by Wang and Liao. (-)-Lasubine I (67) is a bioactive alkaloid isolated from the Lythraceae plant.(-)-Lasubine I contains three stereocenters in a quinolizidine core. Roush allylation of aldehyde 63 with provided the 1,3-aminoalcohol 67 in > 90 < 10 diastereoselectivity. Alcohol protection and alkene oxidation provided an intermediate aldehyde which underwent Roush allylation with to provide homoallylic... 

The Lythraceae plants produce a large variety of bioactive alkaloids. A number of them comprise the quinolizidine scaffold, such as (—)-lasubine I and II. liao el al. 

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