B.R.S.M. Yield isn't everything


Cyanthiwigins B, F, and G

Total Syntheses of Cyanthiwigins B, F, and G

Stoltz et al., Chem. Eur. J., 2011, Early View; [PDF] [SI] [GROUP]

DOI: 10.1002/chem.201100425

I briefly contemplated not covering this, as I covered the Stoltz group conquest of liphagal last month,[1] and this uses the same palladium-catalysed enantioselective decarboxylative alkylation as the key asymmetry creating step. However, this is such a clever and powerful demonstration of the methodology that I couldn't help myself.[2] This time the targets are the cyanthiwigins, a family of marine diterpenoids with over 30 members, all sharing a highly conserved 5-6-7 tricyclic core. The few members isolated in sufficient quantity for testing, and the cyathanes in general, have demonstrated a range of biological activities so new routes to these compounds could be useful.

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Neodysiherbaine A

A Short and Efficient Synthesis of Neodysiherbaine A by Using Catalytic Oxidative Cyclization

T. J. Donohoe et al., Angew. Chem. Int. Ed., 2011, Early View; [PDF][SI][GROUP]

DOI: 10.1002/anie.201102525

Isolated a decade ago from a marine sponge, neodysiherbaine A is an excitatory amino acid and a powerful convulsant and glutamate receptor antagonist. There've been four syntheses to date; two by Sakai and coworkers in 26 and 23 steps respectively, one by Hatakeyama in 21 steps, and a considerably shorter one by Lygo and coworkers in 15 steps. Tim Donohoe and his group at Oxford saw room for improvement again, and published yesterday a sweet seven step synthesis showcasing their Osmium based methodology for the oxidative formation of cis-tetrahydrofuran rings.

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