Oxidative oxomaritidine

Oxidative phenolic coupling. Biosynthesis of the alkaloid narwedine (3) is known to involve oxidative phenolic coupling of norbelladine derivatives (1), but the usual oxidants for such coupling in vitro convert 1(R = H) into the oxomaritidine skeleton (4) rather than 3. A new biomimetic synthesis of 3 involves the palladacycle 2, formed by reaction of 1(R = CH3) with Li2PdCl4, which is known to form complexes with allylic amines or sulfides (8,176-177). Oxidation of 2 with thallium(III) trifluoroacetate effects the desired coupling to give 3. 

The seven-step flow synthesis of ( )-oxomaritidine included the oxidation of benzylic alcohol 25 to aldehyde 26 (Scheme 4.67) using polymer-supported tetra-N-propylammonium perruthenate (TPAP) 27. Although this reaction is stoichiometric in ruthenium, the Ru(VII) species can be readily regenerated by flowing a solution of NMO through the spent reagent cartridge [89]. 

Studies directed toward the synthesis of amaryllidaceae alkaloids provide instructive examples of the combined use of spirocylization and Michael addition pathways in phenolic oxidations (03MI1). For example, treatment of the norbelladine derivative 164 with BTIB leads, by way of C,C-bond formation, to the spiroannulated azepine 165 (Scheme 47) (96JOC5857, 98JOC6625). Hydrolysis of the amide moiety in 165 results in Michael addition of the nitrogen center to the dienone ring and affords ( )-oxomaritidine (166). BTIB-oxidation of the appropriate... 

The synthesis of ( )-oxomaritidine (192) and a formal synthesis of (+)-maritidine (178) were achieved by intramolecular oxidative coupling of phenol derivatives using a hypervalent iodine reagent as a key step 143). 2-[(4-Hydroxy)phenyl]-A/ -[(3,4-dimethoxy)phenyl]-A -trifluoroacetyl-ethylamine was treated with phenyliodonium bis(trifluoroacetate) in... 

Biogenetic-type syntheses of ( )-oxocrinine (21a) and ( )-oxomaritidine (21b) by an anodic oxidation procedure have been achieved. Thus oxidation of the trifluoroacetyl derivative (22a) in acetonitrile solution using platinum electrodes and fluoroboric acid electrolyte gave the spirodienone (23a) in 62% yield. Compound (23a) was readily converted into ( )-oxomaritidine (21b) by known procedures. This represents the highest observed yield of a phenol oxidative... 

A formal total synthesis of c//-maritidine, utilizing the photochemical cyclization of a bromoaromatic compound (i, x=Br) in one step to the crinan ring system (ii) has been reported by T. Kametani, T. Kohno, S. Shibuya and K. Fukumoto, Chem. Commun., 774 (1971). Oxomaritidine is also obtained in good yield via anodic oxidation of the... 

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