Callipeltosides A, B & C: Total Syntheses and Structural Confirmation
Frost, James R
Pearson, Colin M
Snaddon, Thomas N
Booth, Richard A
Shaw, David M
Chemistry - a European Journal
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Frost, J. R., Pearson, C. M., Snaddon, T. N., Booth, R. A., Turner, R., Gold, J., Shaw, D. M., et al. (2015). Callipeltosides A, B & C: Total Syntheses and Structural Confirmation. Chemistry - a European Journal, 21 13261-13277. https://doi.org/10.1002/chem.201501877
Since their isolation almost 20 years ago, the callipeltosides have been of long standing interest to the synthetic community owing to their unique structural features and inherent biological activity. Herein we present our full research effort that has led to the synthesis of these molecules. Key aspects of our final strategy include a) synthesis of the C1–C9 pyran core (5) using a AuCl3-catalysed cyclisation; b) formation of C10–C22 vinyl iodide (55) via sequential bi-directional Stille reactions and c) diastereoselective union of these advanced fragments by means of an alkenylzinc addition (dr = 91:9 at C9). The common callipeltoside aglycon (4) was completed in a further 5 steps. Following this, all 3 sugar fragments were appended to provide the entire callipeltoside family. In addition to this, D-configured callipeltose B was synthesised and appended to the callipeltoside aglycon. The 1H NMR of this molecule was found to be significantly different to the natural isolate, further supporting our assignment of callipeltoside B (2).
callipeltoside, organocatalysis, gold catalysis, cross coupling, glycosidation
We thank Novartis for a research studentship (J.R.F) and also gratefully acknowledge the EPSRC (Award numbers: EP/F06985/1; EP/K009494/1; EP/K039520/1) for financial support (C.M.P., T.N.S., R.A.B., J.G. and D.M.S).
External DOI: https://doi.org/10.1002/chem.201501877
This record's URL: https://www.repository.cam.ac.uk/handle/1810/248729
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Licence URL: http://creativecommons.org/licenses/by/2.0/uk/