- Acid-catalyzed reactions of sarcophytoxide, a marine cembranoid: An apparently enantio-directive reaction, unusual products and stereochemical reconsideration of epoxide-ketone rearrangement
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Perchloric acid treatment of sarcophytoxide, a marine cembranoid possessing an epoxide, brought about epoxide ketone rearrangement affording ketones. When the reaction time was long (22 h), a minor ketone that was antipodal to the ketone obtained in a short-time (l0min) reaction was formed. These puzzling findings, considering that the starting epoxide had three asymmetric carbons, were interpreted by surveying the structures of other ketonic products. The stereochemistry of a major ketone, which had been wrongly assigned, was corrected by extensive analyses of NMR spectra. The correct stereochemistry indicated that the epoxide-ketone rearrangement took a course via a cationic intermediate.
- Nii, Keiji,Tagami, Keiko,Rijima, Masaru,Munakata, Tatsuo,Ooi, Takashi,Kusumi, Takenori
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experimental part
p. 562 - 573
(2009/04/10)
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- STUDIES OF AUSTRALIAN SOFT CORALS. XLV. EPOXIDATION REACTIONS OF CEMBRANOID DITERPENES: STEREOCHEMICAL OUTCOMES
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Epoxidation of the cembranoid diterpene (1) afforded the known 7S,8S-epoxide (2), the 7R,8R-epoxide (3), the 11R,12R-epoxide (4) and the 11S,12S-epoxide (5) in the ratio 1:3:3:10.Similar epoxidation of the cembranolide (1R,2R,3E,7E,11E)-cembra-3,7,11,15-tetren-17,2-olide(6) afforded the 7S,8S-epoxide (7), the 7R,8R-epoxide (8), the 11R,12R-epoxide (9) and the 11S,12S-epoxide (10) in the ratio of 1:5:6:8.Only one of the products (8), from the second epoxidation reaction was known.The other three compounds are reported for the first time.This study reveals a significant preference for epoxidation at the 11,12-double bond.No evidence of epoxidation at the 3,4-double bond was detected in either system.
- Bowden, Bruce F.,Coll, John C.
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p. 669 - 672
(2007/10/02)
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