Exp 13 C NMR Chemical Shift Assignments for Gammacerane (Tetrahymane)

摘要

The carbon-13 NMR chemical shift values were obtained and assigned for each carbon atom of the pentacyclic triterpane gammacerane. Thirteen resonances of nearly unit intensity and one resonances of approximately two intensity units were observed which supports the proposed C sub 2 symmetry. The assignments were made by comparison with similar molecules and off-resonance decoupling. Relative to podocarpane C-7 and C-9 resonances of gammacerane were found to be shifted upfield instead of the expected downfield shift. These shifts are attributed to subtle conformational effects and an accentuated gamma -effect due to the rigidity of the carbon skeleton. (ERA citation 05:027562)