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【答案】应助回帖
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爱与雨下(金币+2): 2011-12-12 08:35:01
hmily601(金币+100, 翻译EPI+1): 辛苦了啊！！！呵呵 2011-12-12 22:12:07
After checking the relevant references, when only one rhamnose base directly connected at the position of C-7 or C-3 in kaempferol molecule, the first hydrogen-based signal chemical shift for rhamnose was about 5.2 ppm. We could determine the two rhamnose base which can not be directly connected at the position of C-7 and C-3 in the mother of kaempferol according to the first hydrogen of sugar-based groups chemical shift values and coupling constants of the compound 1. Instead, it can only be directly connected at the position of C-7 and C-3 in galactose mother kaempferol. For C-NMR spectra of compound 1, there was two overlap for the chemical shift signal (100.1 and 100.7 ppm) for the ends carbon of the six glycosylation. In addition, the carbon chemical shifts at four positions of C-2, C-3, C-4, C-5 sugar-based groups are concentrated in the 68.2-76.4 ppm, and there was a severe overlap in the range of 68.2-71.9 ppm. Besides, the chemical shifts signal for methyl carbon of rhamnose is also very similar which are 17.7ppm and 17.9ppm. Thus, according to the condition of their chemical shift distribution and overlap for the six carbons in sugar-based groups, it was indicated that C-7 and C-3 position in kaempferol parent on the sugar chain was in a very similar chemical environment. It was further determined through the relevant literature [13-15] that the sugar chains connected at C-7 and C-3 bits of kaempferol parent are identical and the structure of such sugar chain should be galactose-galactose-rhamnose.
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