Carbon-13 NMR study of (20,24)-epoxydammarane triterpenes |
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| Authors: | Cosme G Francisco Raimundo Freire Rosendo Hernndez Jos A Salazar Ernesto Surez Manuel Corts |
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| Institution: | Cosme G. Francisco,Raimundo Freire,Rosendo Hernández,José A. Salazar,Ernesto Suárez,Manuel Cortés |
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| Abstract: | Assignments of the 13C NMR signals of the dammarane triterpenes, 3β,25,30-trihydroxy-(20R,24R)-epoxydammaran-16-one 3,30-diacetate (trevoagenin A diacetate) (2), its 20S-isomer (trevoagenin B diacetate) (3) and their related (20R)-3β,30-diacetoxy-16-oxo-25,26,27-trisnordammarane-24,20-lactone (4) and its 20S-isomer (5) have been achieved. Suitable tetrahydrofuran models have been synthesized in order to aid the 13C NMR assignments of the side-chain carbons of the above-mentioned compounds. The remarkable chemical shift differences observed for C-21 and C-22 between each pair of the C-20 epimers (2, 3 and 4, 5) allowed the confirmation of the C-20 stereochemistry of these ocotillol-type dammarane triterpenes. |
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