gem -Dihalogenocyclopropanes as building blocks in natural product synthesis: enantioselective total syntheses of ent -erythramine and 3- epi -erythramine
Date
2007
Authors
Stanislawski, Pauline
Willis, Anthony
Banwell, Martin
Journal Title
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Volume Title
Publisher
Wiley-VCH Verlag GMBH
Abstract
ent-Erythramine ((-)-1), the enantiomer of the alkaloid erythramine, was prepared in 15 steps from known compounds. The first of three pivotal bond-forming steps in the synthesis was a Suzuki-Miyaura cross-coupling reaction of the starting materials to give a bis-silyl ether. The second involved silver(I)-induced electrocyclic ring opening of the gem-dichlorocyclo-propane formed in the next step and trapping of the ensuing π-allyl cation by the tethered nitrogen atom to give, following cleavage of the allyloxycarbonyl protecting group, an approximately 5:6 mixture of the chromatographically separable diastereoisomeric spirocyclic products. In the third critical bond-forming reaction, the iodide formed from one of the diastereoisomers underwent a radical-addition/ elimination reaction sequence that led to (-)-1 in 89% yield. The application of the same sequence of transformations to the other diastereoisomer afforded 3-epi-(+)-erythramine (3-epi-(+)-1).
Description
Keywords
Keywords: 1,3 benzodioxole derivative; biological product; cyclopropane derivative; erythramine; isoquinoline derivative; nitrogen; unclassified drug; article; chemistry; infrared spectroscopy; liquid chromatography; mass spectrometry; nuclear magnetic resonance sp Alkaloids; Cyclopropanes; Radical reactions; Spirocyclization; Total synthesis
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Source
Chemistry - An Asian Journal
Type
Journal article
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2037-12-31