A concise and versatile approach toward the preparation of the cyanthiwigin family of cyathane natural products is described. By leveraging a unique double asymmetric catalytic alkylation procedure it is possible to quickly establish two of the most critical stereocenters of the cyanthiwigin framework with high levels of selectivity and expediency. The synthetic route additionally employs both a tandem ring-closing cross-metathesis reaction, and an aldehyde-olefin radical cyclization process, in order to rapidly arrive at the tricyclic cyathane core of the cyanthiwigin molecules. From this unifying intermediate, the preparations of cyanthiwigins B, F, and G are attained swiftly and without the need for protecting groups.
This publication is based on work supported by Award No. KUS-11-006-02, made by King Abdullah University of Science and Technology (KAUST). The authors wish to thank NIH-NIGMS (R01M080269-01), Amgen, Abbott, Boehringer Ingelheim, Merck, and Bristol-Myers Squibbs, GlaxoSmithKline, Johnson and Johnson, Amgen, Merck Research Laboratories, Pfizer, Novartis, Roche, Abbott Laboratories, Boehringer-Ingelheim, AstraZeneca, and Caltech for financial support. We also wish to thank Dr. M. W. Day and Mr. L. M. Henling for X-ray crystallographic expertise, Dr. Andrew Harned, Dr. David White, Daniel Caspi, and J. T. Mohr for helpful discussions, and Professor Mark T. Hamann for authentic samples and spectra of cyanthiwigins B, F, and G. Ruthenium olefin metathesis catalysts were generously donated by Materia.