Porantheridine

In the final steps of a synthesis of (—)-porantheridine 187, hydrogenation of ketal 186 induced its N- and O-deprotection, which was followed by spontaneous cyclization under acidic conditions (Scheme 33) < 1999JOC8402>. 

The main alkaloid, porantherine (C15H23N mp 36-40° [a]D +29°) was shown, by X-ray analysis, to have structure 153. Other spectral studies are consonant therewith (140). Two further alkaloids have been reported and their structures have also been elucidated by X-ray methods. Poranthericine (C15H27ON oil [a]D —20° B.HBr, mp 308°) has structure 154. Its acetyl derivatives (oil) was also isolated from the plant. Porantheridine (C15H270N oil [a]D -26° B.HBr, mp 165-166° [a]D —19°) has structure 155 (140-142). 

Modified syntheses of porantherilidine (24) and porantheridine (23) (cf. Vol. 11, p. 68) from the common intermediate (22) have been described (Scheme 4).22... 

A novel modification of the well-known Comins dihydropyridone methodology was used in the first asymmetric synthesis of (- )-porantheridine (416) (Scheme 54) (379). Addition of the kinetically generated zinc enolate of pentan-2-one to the chiral... 

The structures of the azaphenalene alkaloids of Poranthera corymbosa, poran-therine, porantheridine, poranthericine (51), and O-acetylporanthericine (52) and a related quinolizidine were determined by X-ray analysis (Vol. 5 of these Reports). The isolation and characterization of these alkaloids has now been described in full, and the structure of a new base, porantheriline (53), has been established. ... 

Details of the X-ray crystallographic studies which established the molecular structures and absolute configurations of the interesting alkaloids porantherine, porantheridine, ° and poranthericine (80) have been published. 

Super-Hydride will reduce ketones and aldehydes, of course, but it is not used extensively unless the stereochemistry of the alcohol product can be influenced by this reagent and there are no other groups in the molecule that are reduced by this reagent. In Lhommet s synthesis of (-)-porantheridine, reduction of the ketone unit in 140 gave a 4 1 mixture of 141 and 142, in 99% yield.Esters are also reduced to alcohols, even in the presence of a lactam. 74 j e nucleophilicity of Super-Hydride usually leads to 1,2-reduction of... 

Scheme 15.122 Cyclohydroamination of hydroxyamines with allenes yielding isoxazolidines, which is a common intermediate toward sedamine, nupharamine, and porantheridine.

David, M. Dhimane, H. Vanucci-Bacque, C. Lhommet, G. Efficient Total Synthesis of Enantiopure (-)-Porantheridine J. Org. Chem. 1999, 64, 8402-8405. 

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