Lythraceae alkaloids synthesis

This is a key stage in the synthesis of lactonic Lythraceae alkaloids published by Hanaoka et al., Loev et al., and Wrobel and Gol biewski. This reaction was studied by several groups of chemists (64, 66-69). It proceeds in good yield for a variety of aromatic aldehydes usually in dilute aqueous or alcoholic solutions of sodium hydroxide to yield 2-quinolizidones. Two diastereomers, 138 and 139, defined by the relative stereochemistry at C-4 and C-10 are formed in the condensation In the trans-quinolizidone (139) the C-4 and C-10 hydrogens are trans to one another. In the cw-quinolizidone (138) they are cis. 

Decaline (43) was the first synthesized Lythraceae alkaloid. The synthesis was achieved independently and concurrently by a Japanese and a Polish group. Three approaches were used in these syntheses. In the first method,... 

Once again the azaphenalene, Nuphar, and Lythraceae alkaloids are included in this Chapter. Perhaps the most notable achievement of the year is the synthesis of azaphenalenes of ladybird beetles by Ayer and co-workers.Amongst the new alkaloids, the novel pyridone quinoiizidine, mamanine (3) and its tetrahydro-derivative, pohakuline (5) are of special interest. ... 

There is still considerable activity in the synthesis of Lythraceae alkaloids, although no new methods have emerged this year. Details have appeared of two independent syntheses of the biphenyl ether alkaloid decaline. - Arata s approach to the synthesis of decaline (35) cf. Vol. 5) has been applied to lagarine (36), using a benzyl group to protect the phenolic hydroxyl substituent. 4-Arylquinolizid-2-ones, cf. (34), are important synthetic intermediates, and their synthesis from isopelletierine and a variety of 2-bromobenzaldehyde derivatives has been studied. ... 

A number of new alkaloids have been isolated and stereochemical studies by the Polish group have been extended, but the greatest advances this year have been in the synthesis of Lythraceae alkaloids. 

There has been considerable development during the year in the chemistry of lythraceae alkaloids containing quinolizidine ring systems, especially in synthesis. 

After the recent considerable activity in the synthesis of macrocyclic Lythraceae alkaloids, published work this year has been confined to the isolation of the new aryl-quinolizidine alkaloids desmethoxyabresoline (28) and 10-ep/-desmethoxyabresoline (29) from Heimia salicifolia The structure of alkaloid (28) was established by spectroscopy and by conversion into two known compounds, the alcohol (27) (c/. Vol. 6, p. 97) obtained by basic hydrolysis and... 

In 1999, Kiindig et al. disclosed a highly efficient synthesis of (-)-lasubine (85), a phenylquinolizidine from the Lythraceae family of alkaloids (Scheme 15)... 

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... 

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