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Full Paper
Total Synthesis of Candicanoside A, a Rearranged Cholestane Disaccharide, and Its 4″-O-(p-Methoxybenzoate) Congener
Article first published online: 28 NOV 2008
DOI: 10.1002/ejoc.200800879
Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Additional Information
How to Cite
Tang, P. and Yu, B. (2009), Total Synthesis of Candicanoside A, a Rearranged Cholestane Disaccharide, and Its 4″-O-(p-Methoxybenzoate) Congener. Eur. J. Org. Chem., 2009: 259–269. doi: 10.1002/ejoc.200800879
Publication History
- Issue published online: 2 JAN 2009
- Article first published online: 28 NOV 2008
- Manuscript Received: 10 SEP 2008
Funded by
- Chinese Academy of Sciences. Grant Numbers: KGCX2-SW-213, KJCX2-YW-H08
- National Natural Science Foundation of China. Grant Number: 20621062
- Committee of Science and Technology of Shanghai. Grant Number: 07DZ22001
Keywords:
- Glycosylation;
- Steroids;
- Synthesis design;
- Natural products
Abstract
Candicanoside A (1) and its 4″-O-(p-methoxybenzoate) derivative 2 are congeners of the novel 24(23→22)abeo-cholestane glycosides that occur in the genus Ornithogalum indigenous to Southern Africa and have remarkable cytostatic activities. These two saponins have been synthesized starting from dehydroisoandrosterone, D-glucose, and L-rhamnose in 37 and 44 steps, respectively. The reaction protocols feature a stereocontrolled stepwise glycosylation with glycosyl imidates as the donors. The synthesis of the rearranged steroid aglycon employs a 20-alkoxy radical-mediated functionalization of the angular 18-methyl group, a Johnson–Claisen rearrangement for the alkylation at C-20, an aldol condensation at C-22, and a photodeconjugation of an α,β-unsaturated lactone as the key steps. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)