Total synthesis of orellanine

The syntheses of the main toxin of Cortinarius Orellanus Fries, orellanine, and of its decomposition product, orelline, are reported. The structures of 3,3',4,4'-tetrahydroxy-2,2'-bipyridyl-N,N'-dioxide for orellanine and of 3,3',4,4'-tetrahydroxy-2,2'-bipyridyl for orelline have been proposed by W.Z. Antkowiak and W.P. Gessner. These two conpounds have now been synthesized starting from the 3,3',4,4'-tetramethoxy-2,2'-bipyridyl which could be obtained in good yields by the nickel-phosphine complex-mediated homo coupling of 2-bromo-3,4-dimethoxy pyridine according to the general procedure previously reported by us. The 3,3',4,4'-tetrahydroxy-2,2'-bipyridyl was obtained by demethylation with hydrobromic acid. The oxidation of this compound with hydrogen peroxide afforded the 3,3',4,4'-tetrahydroxy-2,2'-bipyridyl-N,N'-dioxide. This latter compound was also obtained by the demethylation of the 3,3',4,4'-tetramethoxy-2,2'-bipyridyl-N,N'-dioxide with hydrobromic acid. The products obtained presented physical and spectral properties identical to those of the natural products.