Method of manufacturing buprenorphine and analogues thereof from oripavine

A method of preparing a compound of Formula II, or a salt thereof, from a compound of Formula I:

• wherein in Formula II, R′ represents a linear, branched and/or cyclic alkyl group having 1 to 10 carbon atoms, R″ represents a linear, branched and/or cyclic alkyl group having 1 to 10 carbon atoms, and R′″ represents H or a linear, branched and/or cyclic alkyl group having 1 to 6 carbon atoms, comprising:
• (i) optionally replacing the group R in the compound of Formula I, wherein R is H or methyl, by a group R′ being a linear, branched and/or cyclic alkyl group having 1 to 10 carbon atoms;
• (ii) adding methyl vinyl ketone to obtain 1-[(5α,7α)-17-alkyl-4,5-epoxy-3-hydroxy-6-methoxy-6,14-ethenomorphinan-7-yl]ethanone or 1-[(5α,7α)-17-alkyl-4,5-epoxy-3-alkoxy-6-methoxy-6,14-ethenomorphinan-7-yl]ethanone;
• (iii-a) converting the acetyl group in position 7 into a tertiary alkyl alcohol having a general structure —C—(OH)—(CH3)-R″, wherein R″ represents a linear, branched and/or cyclic alkyl group with 1 to 10 carbon atoms;
• and
• (iv-a) reducing the etheno group in position 18,19 to form the compound of Formula II;
• and
• (v) optionally converting the product from step (iv-a) into an addition salt, preferably a pharmaceutically acceptable salt.