Thesis-Final 03 June 2011 pdf - Jacobs University

Background Chapter 2
Cleavage of all protecting groups was achieved with 1 N aqueous HCl containing 15
% THF. Hydrolysis of the protecting groups was complete after stirring for 10 days at
room temperature. The 5-caffeoyl quinic acid 29 was isolated in 91 % yield Figure
22.
Figure 22: Cleavage of the protecting groups for 5-caffeoyl quinic acid
Synthesis of 1-caffeoyl quinic acid
In a publication of 1964 by Weiss 269 1-caffeoyl quinic acid 31 was synthesised from
the by-product of the the kinetic acetalysation, the protected quinide 26. The caffeic
acid chloride was di-ethylcarbonate protected, but no yield and no conditions were
described in detail. Also in this synthesis the by-product of the kinetic acetalysation,
the protected quinide 26 was used as quinic acid derivate in the esterification step.
According to Rohloff et al. 270 , the ratio of the protected quinide 26 and bisacetonide
25 was changed to 92:8 by using conditions for a thermodynamic acetalization of (-)-
quinic acid 23. This acetalization was accomplished by refluxing (-)-quinic acid 23, p-
toluenesulfonic acid, 2,2 dimethoxy propane (DMP) and acetone for 2 h in 90 % yield
Figure 23.
HO
COOH
thermodynamic
acetalisation +
O
O
O
HO
O
O
HO
OH
OH
O
O
OH
O
O
23 25 26
Figure 23: Thermodynamic acetalisation of quinic acid
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