Preparation of 6,14‐Ethenomorphinane Derivatives Buprenorphine (5j) and diprenorphine (5k) were synthesized from N‐formyl‐northebaine (1c) and N‐benzyl‐northebaine (1d) via new intermediates. N‐cyclopropylmethyl‐dihydronorthevinone 3d is a suitable compound for the synthesis of both 5j and 5k. We carried out detailed 1H‐ and 13C‐NMR analysis of the new compounds.