Compound | Key NMR Observations and Conclusions |
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5 | The location of the hydroxyl group at C15 was assigned based on the presence of a new 4.68/54.0 ppm cross-peak in the 1H-13C HSQC spectrum, signifying a CH2OH group, and the absence of the H15/C15 (2.54/11.0 ppm) cross-peak that was observed in the NMR spectrum of 1. |
6 | The location of the hydroxyl group at C28 was inferred from the presence of a new 4.6/57.0 ppm cross-peak in the 1H-13C HSQC spectrum, signifying a CH2OH group, and the absence of the H28/C28 (2.37/2.35 ppm; 14.2/14.2 ppm) cross-peak. |
7 | The location of the carboxylate group at C28 was inferred from the absence of the H28/C28 (2.37/2.35 ppm; 14.2/14.2 ppm) cross-peak and the absence of other cross-peaks in the 1H-13C HSQC spectrum. |
10 | Only one tautomer was observed. The anomeric proton exhibited a chemical shift of 6.3/90 ppm. Location of the glucuronic acid moiety was inferred from an NOE correlation between the anomeric proton and H18. |
11
| The anomeric 1H/13C of the major and minor tautomers exhibited chemical shifts of 6.0/91 ppm and 6.1/90 ppm, respectively. Location of the GlcNAc moiety was inferred from correlations of C18 to both the anomeric proton and H25 (major tautomer) in the 1H-13C gHMBC spectrum. |