Phytochemistry, 53, 277 (2000)

In this article, the C-NMR data of compound-#1 and compound-#2 have been assigned. The original assignment of compound-#1 is given in the picture below - at the positions 2, 4a and 8a ( = 2,10 and 9 in the paper), a deviation of up to ca. 38.7ppm between experimental and predicted values can be found.

Original assignment

The revised assignment is given below.

Alternate assignment

The next problem is the assignment of the identical side-chain, when comparing compound #1 and #2. In the beta-postion with respect to the C=O group a shielding should be expected ( predicted value: ca. 24ppm ), in compound-#1 no such signal is available, whereas in compound #2 a signal at 23.7ppm is given in the literature, but misassigned to C-2' instead of C-6'.

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Page written on:  March 31st, 2008