Lewis Acid-mediated Diastereoselective Synthesis of Medium-sized Cyclic Ethers and Studies Towards the Synthesis of Plakortolide E and 6-Epiplakortolide E
The Lewis acid-mediated synthesis of medium-sized cyclic ethers has been achieved in a diastereoselective manner. Using TMSOTf or BF3•OEt 2, we developed a novel protocol for the intermolecular synthesis of eight-membered cyclic ethers (oxocenes) via Prins-type cyclization. This methodology displays a unique approach towards 2,4,8-trisubstiituted oxocene cores, with good yields and excellent diastereoselectivity. We have also expanded this protocol to show applicability towards the synthesis of seven-membered rings (oxepines and oxepanes). Progress studies towards the synthesis of plakortolide E and 6-epiplakortolide E are described. Featuring a bicyclic peroxylactone, these compounds are of interest due to their potential antimalarial activity. A key step in these syntheses features a diastereoselective [4+2] cycloaddition with singlet oxygen, under photosensitized conditions.
Ghosh, Purdue University.
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