Coreximine synthesis

On treatment of N-methylpapaverine, formed by the lithium aluminum hydride reduction of papaverine methiodide with phosphoric acid, N-methylpavine is formed which is identical with the racemic alkaloid argemonine. This reaction was used for the synthesis of the alkaloid (-h)-coreximine (268) (174) and similar compounds containing the proto-berberine grouping in the molecule (269,270). 

A second general method for the synthesis of the protoberberine alkaloids has been described by Battersby et al. (116). The method, which utilizes a 1,2-dihydroquinoline as a key intermediate, has been used to synthesize ( + )-norcoralydine (XXXIX R = CH3) and (+ )-coreximine (LXXIX), as illustrated for the latter in Chart III. 

Core valence bifurcation index 75, 76 Coreximine, formation of 1306 Cotitration studies 335 Coulometric arrays 960, 961 Coumarans—see also Phenylcoumarans formation of 753-758 Coumaric acid 1057 Coumarins—see 4-Methylcoumarin Coumestans, synthesis of 1219, 1222 Coupled clusters 3... 

The isolation of the alkaloids of the protoberberine type (102) and the synthesis of columbamine from berberine (101) have been reported. The synthesis of coreximine, scoulerine, and tetrahydropalmatine have been described (59, 235, 236). The synthesis of alkaloids having a protoberberine skeleton has been reviewed (374). 

Details of the synthesis of berberastine via a 3-aryltetrahydroisoquinoline have appeared. In a new modification of this route, separable mixtures of scoulerine (123 R = OH R = H) and coreximine (123 R = H R = OH), stereospecifically labelled with tritium at C-13, have been synthesized from stereospecifically labelled a-tritiobenzyl alcohols (Scheme 11). ... 

When th 0,0-diethyl ether of coreximine was oxidized under conditions which favor the formation of corydaldines there was obtained l-keto-6-methoxy-7-ethoxytetrahydroisoquinoline (XLII), and this serves to locate one hydroxyl at position 2 (LXX). The location of the second hydroxyl could not be carried out by further oxidation of the diethyl ether because only 4-methoxy-5-ethoxyphthalic acid could be formed. It was then assumed that the natural synthesis of coreximine involved ring closure of a benzylisoquinoline and that this could only occur if the condensation posi-... 

Structures assigned to certain tetrahydroberberine alkaloids have been shown to be incorrect, the bases being identified with known compounds by comparison with authentic specimens. The bases concerned are aequaline, coramine, schefferine, kikemanine, and discretinine, which have been shown to be identical with discretamine (56 R =R = H), coreximine (57), (-)-corydalmine (56 R Me, R = H), (-)-corydalmine, and corypalmine (56 R =H, R = Me) respectively. The structure of discretamine has been confirmed by synthesis of the racemate from the tetrahydroisoquinoline (58 R = PhCH2, R = Me) by its... 

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