Synthesis of buprenorphine from oripavine via N-demethylation of oripavine quaternary salts.

Buprenorphine was synthesized from oripavine by a sequence involving the conversion of oripavine into its cyclopropylmethyl quaternary salt, N-demethylation with thiolate to N-cyclopropylmethyl nororipavine, and conversion of this material to the title compound by previously available methods. The new synthesis avoids toxic reagents used previously, is shorter, and proceeds in comparable yields. Experimental and spectral data are provided for all new compounds.