Thesis-Final 03 June 2011 pdf - Jacobs University

Results and discussion Chapter 3
Figure 114: IR spectrum of (1S,3R,4R,5R)-1-cinnamoyl-3-(acetyl p- coumaroyl)
quinide
How to distinguish between the constitutional isomers:
The combination of the NMR spectrometric data which was based on 1 H-NMR, 13 C-
NMR, 1 H 1 H-COSY, HMBC and HSQC techniques as well as careful consideration of
substituent chemical shifts (SCS) contain a lot of information for the assignment of
the correct constitutional isomers. During experimental process it was observed that
the assigned proton shifts are valuable tools in the analysis of quinic acid, quinic acid
esters and their isomers. It was also observed that the acylation of a hydroxyl groups
produces a paramagnetic (downfield) shift of about 1.20-1.4 ppm of the according to
the electronegativity of the substituent.
As an instance of the theory; the 1 H-NMR spectrum of the (1S,3R,4R,5R)-1,3-di-
(acetylferuloyl) quinide (92) exhibited the signals for the two feruloyl moieties and
quinide moiety. After careful consideration of the 1 H-NMR spectrum of the (92) in
comparison with 1 H-NMR spectrum of the quinide (51) showed that there was only
one single significantly deshileded proton signal (H-3 δ= 5.06 ppm) because of the
ester linkage. The same affect was observed with all the other compounds throughout
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