Phytochemistry, 53, 277 (2000)
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.
revised assignment is given below.
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'.
written by: Wolfgang.Robien(-at-)c13nmr.at
Page written on: March 31st, 2008