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Issue 2, 2001
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The β-elimination route to stereodefined γ-alkylidenebutenolidesDedicated to Dr Klaus Brückner (retired from Cela-Merck, Ingelheim) on the occasion of his 75th birthday.

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Abstract

γ-Alkylidenebutenolides are biologically significant compounds and comprise compounds as structurally and functionally diverse as the inhibitor dihydroxerulin (Z-61, Scheme 16) of cholesterol biosynthesis or the carotinoid peridinin (Z-18a, Scheme 5) which plays a dominant role in marine photosynthesis. For the stereo-controlled obtention of γ-alkylidenebutenolides Z-2 or E-2 with or without alkyl substituents at C-α or C-β, a general strategy has been developed (Scheme 1). The key step of this strategy is the stereospecific anti-elimination of water from diastereopure γ-(α-hydroxyalkyl)butenolides lk-1 or ul-1—be they racemic or enantiopure (lk = like, ul = unlike: γ-(α-hydroxyalkyl)butenolides lk-1 give γ-alkylidenebutenolides Z-2, while γ-(α-hydroxyalkyl)butenolides ul-1 furnish the isomeric γ-alkylidenebutenolides E-2. As dehydrating agents we used mixtures of triflic anhydride and pyridine or of diethyl azodicarboxylate and triphenylphosphine. Previous β-eliminations providing γ-alkylidenebutenolides exhibited in general little stereoselectivity and no stereospecifity at all (exception: Scheme 10), irrespective of whether this β-elimination was performed separately or took place in situ.

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Article information


Submitted
19 Sep 2000
Accepted
13 Nov 2000
First published
04 Jan 2001

Chem. Commun., 2001, 141-152
Article type
Feature Article

The β-elimination route to stereodefined γ-alkylidenebutenolides

R. Brückner, Chem. Commun., 2001, 141
DOI: 10.1039/B007590F

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