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Cyclofunctionalization and Free-Radical-Based Hydrogen-Transfer Reactions. An Iterative Reaction Sequence Applied to the Synthesis of the C7−C16 Subunit of Zincophorin

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journal contribution
posted on 07.07.2001, 00:00 by Yvan Guindon, Lorraine Murtagh, Valérie Caron, Serge R. Landry, Grace Jung, Mohammed Bencheqroun, Anne-Marie Faucher, Brigitte Guérin
The strategy considered herein features an iodocyclofunctionalization/hydrogen-transfer reaction sequence for the elaboration of propionate motifs. Proceeding with excellent yield and diastereoselectivity, the synthetic sequence proposed gives access to the anti-anti dipropionate motif when the reduction step is performed under the control of the exocyclic effect. The tandem sequence is applied successfully to the synthesis of the C7−C16 subunit of zincophorin, and iteration of the process gives the desired anti-anti-anti-anti polypropionate stereopentad. Modifications of the reaction sequenceincluding phenylselenocyclofunctionalization, carbonate hydrolysis, and chelation-controlled radical reduction reactionslead to the formation of the anti-syn dipropionate motif with remarkable diastereocontrol.