ISSN:
1434-193X
Keywords:
Caffeic acid
;
Carbohydrates
;
Glycosidations
;
Orthoester
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
TMSOTf-mediated condensation of ethyl 4,6-O-benzylidene-1-thio-β-D-glucopyranoside (2) with peracetylated α-L-rhamnopyranosyl trichloroacetimidate donor 3a resulted in the formation of orthoester 4, which, after acetylation, rearranged into ethyl 3-O-(α-L-rhamnopyranosyl)-1-thio-β-D-glucopyranoside derivative 6a. The latter compound was converted into the corresponding trichloroacetimidate donors 8a-b. An alternative approach to trichloroacetimidate 8c commenced with the iodonium ion mediated glycosidation of ethyl 2,3,4-tri-O-benzoyl-1-thio-α-L-rhamnopyranside (15) with 1,2:5,6-diisopropylidene-D-glucofuranose (16) to afford disaccharide 17, which was transformed into 8c in five steps. Condensation of 8a-c with 2-[3,4-di-(tert-butyldimethyl-silyloxy)phenyl]ethanol (12) gave, after deacylation, key intermediate 14. Protecting-group manipulation of 14 and subsequent esterification of resulting 22 with 3,4-di-O-tert-butyldimethylsilylcaffeic acid (27) gave, after deprotection, verbascoside (1).
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
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