Total Synthesis of (–)-Berkelic Acid
Key words(–)-berkelic acid - Catellani reaction - oxa-Michael reaction - nickel catalysis - reductive coupling
Qu, Zhou, and co-workers report a concise total synthesis of (–)-berkelic acid, which was isolated in 2006 from an extremophilic Penicillium species. Their synthesis relies on a Catellani reaction followed by an oxa-Michael addition performed in a one-pot operation and a late-stage Ni-catalyzed reductive coupling.
The synthesis commences with the preparation of enone B, which is accessed from ketone A in four steps. A Catellani reaction/oxa-Michael cascade gives rise to F. Benzyl deprotection followed by spiroacetalization gives ketal G in good yield and excellent diastereoselectivity, setting four stereocenters from only one existing chiral center. Iodide H is then coupled with acid chloride J in a Ni-catalyzed reductive coupling to give methyl ester K. (–)-Berkelic acid is obtained by selective saponification in the presence of (Bu3Sn)2O.
16. Februar 2021 (online)
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