Synthesis and transformations of new dihydro-β-campholenolactone derivatives

The reaction of xenon difluoride with enamino lactone 3 furnished the new α-fluoro aldehyde 7, whereas reaction of 3 with anhydrous HF led to racemic dihydro-β-campholenolactone 6. Acid-catalysed rearrangement of α-ethylidenelactone 4 proceeded with retention of configuration to give β-campholenolactone 8. Nitrosation of the novel bicyclic enamino lactone 6 afforded the corresponding oxime 9, while acid-catalysed treatment with primary amines, 2-methyl-1H-indole, potassium cyanide and hydrazine hydrochloride, furnished the dimethylamine substitution products 11–13 and the ‘ring switched’ product 14. The structures were determined by 2D NMR techniques, NOESY spectroscopy and X-ray diffraction.

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(1R,4R,5S)-4-Fluoro-1,8,8-trimethyl-3-oxo-2-oxabicyclo[3.2.1]octane-4-carbaldehydeC11H15FO3De = 100%[α]D23=-232.6 (c 0.22, CHCl3)Source of chirality: natural (1R)-(+)-camphorAbsolute configuration: (1R,4R,5S)

(3aR,6aS,3E)-3-Ethylidene-6,6,6a-trimethylhexahydro-2H-cyclopenta[b]furan-2-oneC12H18O2De = 100%[α]D23=+185.7 (c 0.28, CHCl3)Source of chirality: natural (1R)-(+)-camphorAbsolute configuration: (3aR,6aS,3E)