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Anomalous Chromophore Disruption Enables an Eight-Step Synthesis and Stereochemical Reassignment of (+)-Marineosin A

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posted on 29.01.2019, 00:00 by Zhengao Feng, Tyler K. Allred, Evan E. Hurlow, Patrick G. Harran
An eight-step asymmetric synthesis of (+)-marineosin A is described. The route proceeds by condensing fragments of reversed polarity relative to conventional prodiginine constructions. The resultant unstable chromophore is disrupted by a unique cycloisomerization promoted at a tailored manganese surface. This provides a premarineosin and subsequently marineosin A in a particularly concise manner. A pyridinophane N-oxide photorearrangement in flow and structural isomers of premarineosin are discussed, as is the reassignment of marineosin stereochemistry. The route gives access to the natural product as well as diastereomers, congeners and analogs that are currently inaccessible by other means.