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Updated: Feb 13, 2026

Dissection and Flat-mounting of the Threespine Stickleback Branchial Skeleton
Published on: May 7, 2016
Favorskii-Type Rearrangement of the 4,5-Epoxymorphinan Skeleton
Noriki Kutsumura1, Yasuaki Koyama2, Yuko Suzuki2
1International Institute for Integrative Sleep Medicine (WPI-IIIS) , University of Tsukuba , 1-1-1 Tennodai , Tsukuba , Ibaraki 305-8575 , Japan.
Abstract:
The aldol condensation of naltrexone with various aryl aldehydes gives the corresponding 7-benzylidenenaltrexone derivatives in high yields. However, novel C-ring-contracted morphinan compounds were produced when 2-pyridinecarboxaldehyde or its related analogues were used as a coupling partner. The key structural feature was the existence of the tetrahydrofuran ring (4,5-epoxy ring, E-ring) of the morphinan skeleton. The time-resolved in situ IR spectroscopy of the reaction system indicated the short-lived absorption of the distorted cyclopropanone intermediate.
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