Face Selectivity of the Diels‐Alder Reaction of Thebaine‐Like Morphinandienes, A Computational Approach (Chemistry of Opium Alkaloids, Part XXXI)

Molecular mechanics {MMP2(85)} have been employed for the calculation of the geometry of morphinan‐6,8‐dienes. The X‐ray structure of desoxycodeine‐A, a morphinan‐5,7‐diene, and of other morphinans were well‐reproduced by the minimization program. The conformations of 4,5α‐epoxymorphinan‐6,8‐dienes and their 4‐hydroxy analogues show considerable differences, which account for the observed face selectivity in the Diels‐Alder cycloaddition.