Research@StAndrews
 
The University of St Andrews

Research@StAndrews:FullText >
Chemistry (School of) >
Chemistry >
Chemistry Theses >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10023/2009
This item has been viewed 22 times in the last year. View Statistics

Files in This Item:

File Description SizeFormat
KolawoleRaheemPhDThesis.pdf6.21 MBAdobe PDFView/Open
Title: Studies on the synthesis of dicaffeoylquinic acid conjugates
Authors: Raheem, Kolawole Saki
Supervisors: Botting, Nigel P.
Keywords: Dicaffeoylquinic acids
Natural products
Plant natural products
Issue Date: Nov-2011
Abstract: Dicaffeoylquinic acid (DCQA) is a natural polyphenolic compound widely distributed in plants such as coffee beans, which possesses a range of pharmacological activities. Herein, is reported studies undertaken towards the first total synthesis of 3,5-DCQA conjugates. Two synthetic routes were investigated. The first route involves a seven step sequence beginning from quinic acid. The overall yield via this synthetic approach was 30%. The key steps involved in the sequence were a regioselective benzylation of the C-3-hydroxyl group followed by silyl protection of the C-1 and C-4 hydroxyl groups. Deprotection of the benzyl group by hydrogenolysis and opening of the lactone afforded the 3,5-diol. Esterification of the 3,5-diol with 3,4-tert-butyldimethylsilyl caffeoyl chloride afforded the di-ester. Removal of the protecting groups afforded 3,5-DCQA. The second route involved selective protection of the C-3-hydroxyl group with silyl followed by benzylation of the C-1 and C-3 hydroxyl groups. Saponification of the lactone ring followed by benzylation of the carboxylic acid gave the benzyl ester. Silyl deprotection afforded the 3,5-diol. The 3,5-diol was subsequently esterified by refluxing in toluene with commercially available Meldrum’s acid. In the final step, the synthesis of 3,5-DCQA was achieved by a Knoevenagel condensation of 3,4-dihydroxybenzaldehyde and a malonate ester of quinic acid. An efficient method for the synthesis of possible metabolites of quinic acid conjugates was also described. This protocol employs N-(4-methoxyphenyl)-trifluoroacetimidate glucuronyl as the donor. The key reaction in this sequence was the coupling of N-(4-methoxyphenyl)-trifluoroacetimidate glucuronyl with 4-hydroxy-3-methoxy-benzaldehyde.
URI: http://hdl.handle.net/10023/2009
Other Identifiers: uk.bl.ethos.552610
Type: Thesis
Publisher: University of St Andrews
Appears in Collections:Chemistry Theses



This item is protected by original copyright

This item is licensed under a Creative Commons License
Creative Commons

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

DSpace Software Copyright © 2002-2012  Duraspace - Feedback
For help contact: Digital-Repository@st-andrews.ac.uk | Copyright for this page belongs to St Andrews University Library | Terms and Conditions (Cookies)