The treatment of morphinan I with NaH and MsCl provided very stable iminium salt 7 possessing propellane skeleton. One of the synthesized iminium salts 7, isobutyl derivative 7b, was crystallized and its structure was determined by X-ray crystallography. The natural bond orbital analysis suggested that the stability of the iminium should result from the stereoelectronic effect (hyperconjugation) attributed to their own structures.
Synthesis of new opioid derivatives with a propellane skeleton and their pharmacology: Part 1
The observation that 17-cyclopropylmethylmorphinan derivatives without the 4,5-epoxy ring showed more κ selectivity than those with a 4,5-epoxy ring led us to develop a working hypothesis: the position of the plane composed of the A and B rings would influence the opioid receptor type selectivity and that the decrease in the torsion angle C11–C12–C13–C14 could improve the κ selectivity. Consistent