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Totally Synthetic by Paul H. Docherty, 15 December 2006

Total Synthesis of ()-11-O-Debenzoyltashironin


S. P. Cook, A. Polara, S. J. Danishefsky, J. Am. Chem. Soc. 2006, 128, 16440-16441.

DOI: 10.1021/ja0670254

A very quick total synthesis of this compact yet complex natural product, albeit in its racemic form. Danishefsky et al. decided to use a rather impressive oxidative dearomatization to construct one ring, allowing a further intramolecular Diels-Alder reaction to complete the core. But they had to make the cyclisation substrate first:

Functionalisation of the aromatic ring was completed easily, with a formylation and bromination of a m-hydroxy-phenol delivering the electrophilic component for a Stille reaction. Coupling to an allyl silane, and elimination of a mesyl group then finished the cyclisation substrate, which was treated with phenyliodine-(III) diacetate (PIDA):

Good job! Completing the natural product really took relatively few transformations; the Prilezhaev reaction produced only the desired epoxide, and the exocyclic double-bond was reduced with Wilkinson's catalyst. Opening of the epoxide with superhydride and oxidation/deprotection then returned the target. Nice work!