Kreysigine, synthesis

From L-tyrosine, and alternatively also from L-phenylalanine, kreysigine synthesis begins with dopamine (Figure 36). -autumnaline is derived via a Mannich-like reaction. 5 -autumnaline is converted into floramultine by the oxidative coupling. Subsequently, the kreysigine is synthesized through the... 

Scheme 19. An approach to the synthesis of kreysigine by iran (I II)-mediated intramolecular oxidative coupling.

The structure of this base and some of its congeners was proved by exhaustive spectral data as well as by a synthesis. The diphenol LXXII (R = OMe) prepared by standard procedures was oxidized by alkaline ferricyanide to LXXIII (R = OMe) which is thus a ring homologue of the proaporphines. This product rearranged in concentrated sulfuric acid to yield LXXIV (R = R2 = R4 = H, R = OMe, R = Me), methylation of which with diazomethane gave a mixture of ( )-kreysigine (LXXIV R = R = H, Ri = OMe, R2 = RS = ] Je) and its 0-methyl ether. Deacetyl-colchicine was also found in the plant from which these alkaloids were isolated (114). Shortly after the above was reported there appeared a... 

The synthetic method using p-quinol acetates to prepare aporphines has been extended to the synthesis of ( )-kreysigine (220). Treatment with acid of the p-quinol acetate (225a) derived from ( + )-(225) gave ( )-0-acetylkreysigine in 18%yield.2 5... 

Base-catalyzed photolyses of 2 -bromo-7-hydroxytetrahydrophenethyl-isoquinolines have resulted in the synthesis of the homoaporphines kreysigine " and alkaloid CC-24. ... 

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