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Forskolin Editing via Radical Iodo- and Hydroalkylation

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Pruteanu Elena, Tappin Nicholas D. C., Gîrbu Vladilena, Morarescu Olga, Dénès Fabrice, Kulciţki Veaceslav, Renaud Philippe,
Project Synthetic Methods for Total Synthesis of Natural Products
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Original article (peer-reviewed)

Journal Synthesis
Volume (Issue) 53(07)
Page(s) 1247 - 1261
Title of proceedings Synthesis
DOI 10.1055/s-0040-1706003


AbstractThe modification of highly oxygenated forskolin as well as manoyl and epi-manoyl oxide, two less functionalized model substrates sharing the same polycyclic skeleton, via intermolecular carbon-centered radical addition to the vinyl moiety has been investigated. Highly regio- and reasonably stereoselective iodine atom transfer radical addition (ATRA) reactions were developed. Unprotected forskolin afforded an unexpected cyclic ether derivative. Protection of the 1,3-diol as an acetonide led the formation of the iodine ATRA product. Interestingly, by changing the mode of initiation of the radical process, in situ protection of the forskolin 1,3-diol moiety as a cyclic boronic ester took place during the iodine ATRA process without disruption of the radical chain process. This very mild radical-mediated in situ protection of 1,3-diol is expected to be of interest for a broad range of radical and non-radical transformations. Finally, by using our recently developed tert-butyl­catechol-mediated hydroalkylation procedure, highly efficient preparation of forskolin derivatives bearing an extra ester or sulfone group was achieved.