Briarellin

During the first total synthesis of briarellin diterpenes, briarellins E and F, L.E. Overman and co-workers utilized the large reactivity difference between a triple and a double bond in peroxyacid oxidations to selectively epoxidize a trisubstituted double bond in the presence of a terminal alkyne." The epoxidation with mCPBA was carried out in DCM in the presence of a base to afford the a-epoxide in a 9 1 diastereomeric ratio. 

The Prins-pinacol rearrangement was utilized during the first enantioselective total synthesis of briarellin diterpenes by L.E. Overman and co-workers. The cyclohexadienyl diol substrate was condensed with a (Z)-a,p-unsaturated aldehyde at low temperature in the presence of catalytic amounts of acid and MgS04 as dehydrating agent. The initially formed acetal was then exposed to 10 mol% of SnCU to afford the desired tetrahydroisobenzofuran as a single stereoisomer that was later converted to briarellin F. 

Corminboeuf, O., Overman, L. E., Pennington, L. D. Enantioselective Total Synthesis of Briarellins E and F The First Total Syntheses of... 

Briarellins are a class of eunicellin diterpenes isolated from the gorgonians Pachyclavularia violacea and Briareum polyanthes [88]. 

Fig. (28) Chemical structures of the moderately active briarellin L (69) and of the inactive briarellin J (70)...

SCHEME 16.7. Synthesis of vigulariol, briarellin J, and ll-acetoxy-4-deoxyasbestinin D. 2005 2010 2011 American Chemical Society. All rights reserved. 

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