Syntheses related to northebaine. Part I. Northebaine and N-allyl-northebaine
Northebaine and N-allylnorthebaine have been synthesised from dihydronorcodeinone. O-Methylation of N-benzyloxycarbonyldihydronorcodeinone followed by hydrogenolysis with triethylsilane gave 8,14-dihydronorthebaine. Addition of methyl hypobromite and subsequent dehydrobromination gave norcodeinone dimethyl ketal, which underwent acid-catalysed elimination of methanol to yield northebaine, and thence, by alkylation, N-allylnorthebaine. Analogous procedures led to N-cyclopropylmethylnorthebaine and N-t-butoxycarbonylnorthebaine, and mild acidic treatment of the latter afforded an alternative route to northebaine. The spectral properties of the new compounds are discussed.