Gymnomitrene

Scheme 3.51. Proposed mechanism for the "round trip" synthesis of iso-gymnomitrene ketone (3-191) and gymnomitrene ketone (3-194).

Full details of two of the elegant syntheses of gymnomitrol (159)93 94 and gymnomitrene (160)94 have been published. 

Haney, B.P., and Curran, D.P., Round trip radical reactions from acyclic precursors to tricy-clo[5.3.1.0 - ]undecanes. A new cascade radical cyclization approach to ( )-isogymnomitrene and ( )-gymnomitrene, J. Org. Chem., 65, 2007, 2000. 

Gymnomitrol (123) and P-barbatene (=gymnomitrene) (122) have been isolated from Gymnomitrion obtusum (Jungermanniales) 108). Further study of the sesquiterpenoids from the same species revealed the presence of six new compounds (124—129) containing the same skeleton 109). These structures were established by a combination of H-NMR and Eu(FOD)3-induced spectral shifts, decoupling experiments, and extensive chemical transformations, which are summarized in Schemes 14a and b 109). 

An independent study of the essential oil of Barbilophozia species resulted in the isolation of two new sesquiterpene hydrocarbons, a-bar-batene (121) and P-barbatene (= gymnomitrene) (122) 3, 4). The LIS-induced H-NMR spectra of an allylic alcohol (149) and an enal (150) prepared from (122) were compared with those of myrtenol and myrtenal (20), thus leading to isogymnomitrene (121), an acid isomerization product of gymnomitrene (122), and to (122) as structures for a- and P-barbatene. The absolute stereochemistry assigned to gymnomitrol was further confirmed by comparing the CD spectra of the barbatenes (121,122) with those of the cedrenes (256, 257) (Scheme 15) (3, 4). 

Matsuo et ai (216) reported isolation of an unusual sesquiterpene hydrocarbon, a-pompene, from Bazzania pompeana, together with P-pompene and proposed structure (151) for a-pompene. The spectral data of a- and P-pompenes were identical with those of a-barbatene (121) and p-barbatene (=gymnomitrene) (122), respectively. That a-pompene is indeed identical with a-barbatene (121), has been shown by X-ray... 

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