Free-Radical-Mediated Conjugate Additions. Enantioselective Synthesis of Butyrolactone Natural Products:  (−)-Enterolactone, (−)-Arctigenin, (−)-Isoarctigenin, (−)-Nephrosteranic Acid, and (−)-Roccellaric Acid

Lewis acid-mediated conjugate addition of alkyl radicals to a differentially protected fumarate 10 produced the monoalkylated succinates with high chemical efficiency and excellent stereoselectivity. A subsequent alkylation or an aldol reaction furnished the disubstituted succinates with syn configu...

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Bibliographic Details
Published in:Journal of organic chemistry 2002-03, Vol.67 (6), p.1738-1745
Main Authors: Sibi, Mukund P, Liu, Pingrong, Ji, Jianguo, Hajra, Saumen, Chen, Jian-xie
Format: Article
Language:English
Subjects:
4-Butyrolactone - analogs & derivatives
4-Butyrolactone - chemical synthesis
4-Butyrolactone - chemistry
Alkylation
Biological Products - chemical synthesis
Biological Products - chemistry
Catalysis
Chemistry
Chemistry, Organic - methods
Exact sciences and technology
Free Radicals - chemistry
Fumarates - chemistry
Furans - chemical synthesis
Furans - chemistry
Heterocyclic compounds
Heterocyclic compounds with o, s, se, te hetero atom and condensed derivatives
Lactones - chemistry
Lignans - chemical synthesis
Lignans - chemistry
Magnetic Resonance Spectroscopy
Molecular Structure
Organic chemistry
Preparations and properties
Stereoisomerism
Succinates - chemistry
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Summary:Lewis acid-mediated conjugate addition of alkyl radicals to a differentially protected fumarate 10 produced the monoalkylated succinates with high chemical efficiency and excellent stereoselectivity. A subsequent alkylation or an aldol reaction furnished the disubstituted succinates with syn configuration. The chiral auxiliary, 4-diphenylmethyl-2-oxazolidinone, controlled the stereoselectivity in both steps. Manipulation of the disubstituted succinates obtained by alkylation furnished the natural products (−)-enterolactone, (−)-arctigenin, and (−)-isoarctigenin. The overall yields for the target natural products were 20−26% over six steps. Selective functionalization of the disubstituted succinates obtained by aldol condensation gave the paraconic acid natural products (−)-nephrosteranic acid (8) and (−)-roccellaric acid (9). The overall yield of the natural products 8 and 9 over four steps was 53% and 42%, respectively.
ISSN:0022-3263
1520-6904
DOI:10.1021/jo015501x