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PubMed2005

Synthesis, structure, and reactivity of unexpectedly stable spiroepoxy-beta-lactones obtained by epoxidation of 4-alkylidene-2-oxetanones.

We describe the first synthesis of spiroepoxy-beta-lactones obtained via epoxidation of ketene dimers. These compounds display unexpected stability that may be due to a double anomeric effect garnered from analysis of bond lengths by X-ray crystallography of one spirocycle in comparison to calculated bond lengths of related structures. These new strained intermediates display interesting reactivity leading to a butenolide, an alpha-hydroxyketone, a triol, an alpha-chloroketone, and an alpha-azidoketone.

Journal Article↗
PubMed2006

Room temperature Au(I)-catalyzed exo-selective cycloisomerization of acetylenic acids: an entry to functionalized gamma-lactones.

A highly efficient gold-catalyzed cyclization reaction of various functionalized acetylenic acids is described. The cyclizations are conducted in the presence of Au(I) catalyst in acetonitrile at room temperature in a short reaction time. The reaction conditions are compatible with several functional groups, such as ester, alkene, alkyne, chloro, and free or protected alcohol, and lead to original gamma-lactones in good to excellent yields.

Journal Article↗
PubMed2006

Antibody interference with N-acyl homoserine lactone-mediated bacterial quorum sensing.

Many bacterial pathogens coordinate their virulence factor expression in a cell density-dependent manner. This population-dependent coordination of gene expression in bacteria has been termed "quorum sensing" (QS). N-Acyl homoserine lactones (AHLs) are used by over 70 Gram-negative bacterial species as autoinducers. Inhibition of QS signaling might represent a new target for antimicrobial therapy. Here we report the hapten design, synthesis, generation of monoclonal antibodies (mAbs) against AHLs, and the evaluation of these mAbs for their ability to blunt QS signaling and inhibit virulence factor expression in P. aeruginosa. The mAbs can be envisioned as a tool for future investigations into AHL-based QS, which may aid in gaining new insights into the pathogenesis of P. aeruginosa and may ultimately lead to the development of new strategies to combat bacterial diseases.

4-Butyrolactone↗
PubMed2006

Asymmetric modular synthesis of highly functionalized medium-sized carbocycles and lactones via ring-closing metathesis of sulfoximine-substituted trienes.

A modular asymmetric synthesis of medium-sized carbocycles and lactones has been developed that affords highly substituted 7-, 9-, and 11-membered rings. The key steps are (1) the highly diastereoselective synthesis of sulfoximine-substituted homoallylic alcohols from allylic sulfoximines and unsaturated as well as saturated aldehydes, (2) an E-stereoselective alkylation and hydroxyalkylation of sulfoximine-substituted alkenyllithium derivatives, (3) the esterification of sulfoximine-substituted homoallylic alcohols, and (4) the ring-closing metathesis reaction of sulfoximine-substituted trienes with the ruthenium catalyst 8. Two examples for the further synthetic elaboration of the sulfoximine-substituted carbocycles are provided. The selective cleavage of the tert-butyldimethylsilyl group of 12 in the presence of the triethylsilyl group afforded the allylic alcohol 18 which was oxidized to enone 19. A cross-coupling reaction of the sulfoximine-substituted carbocycle 9 with LiCuMe2 furnished the methyl-substituted derivative 20.

Journal Article↗
PubMed1998

ATP-Citrate lyase as a target for hypolipidemic intervention. 2. Synthesis and evaluation of (3R,5S)-omega-substituted-3-carboxy-3, 5-dihydroxyalkanoic acids and their gamma-lactone prodrugs as inhibitors of the enzyme in vitro and in vivo.

A series of (3R,5S)-omega-substituted-3-carboxy-3, 5-dihydroxyalkanoic acids have been synthesized and evaluated as inhibitors of the recombinant human form of ATP-citrate lyase. The best of these have Ki's in the 200-1000 nM range. As the corresponding thermodynamically favored gamma-lactone prodrugs, a number of compounds are able to inhibit cholesterol and fatty acid synthesis in HepG2 cells and reduce plasma triglyceride levels in vivo. The best of these, compound 77, is able to induce clear hypocholesterolemic and hypotriglyceridaemic responses when administered orally to rat and dog. These results provide evidence to support the hypothesis that compounds which inhibit ATP-citrate lyase have the potential to be a novel class of hypolipidemic agent, which possess combined hypocholesterolemic and hypotriglyceridemic activities.

ATP Citrate (pro-S)-Lyase↗
PubMed2001

Synthesis of beta-lactones by the regioselective, cobalt and Lewis acid catalyzed carbonylation of simple and functionalized epoxides.

The PPNCo(CO)(4) and BF(3) x Et(2)O catalyzed carbonylation of simple and functionalized epoxides in DME gives the corresponding beta-lactones regioselectively in good to high yields. The carbonylation occurred selectively at the unsubstituted C-O bond of the epoxide ring, and this reaction tolerates various functional groups such as alkenyl, halide, hydroxy, and alkyl ether.

4-Butyrolactone↗
PubMed2002

Ring-opening iodo- and bromosilation of lactones for the formation of silyl haloalkanoates.

Ring-opening halosilation of lactones with two types of reagents, Et(3)SiH/MeI(PdCl(2)) (1a) and Et(3)SiH/AllylBr(PdCl(2)) (1b), was studied. Cyclic esters such as gamma-butyrolactones, delta-valerolactone, and 6-hexanolide reacted with 1 equiv of 1a,b to give triethylsilyl omega-iodo- and omega-bromoalkanoates in good yields. Reaction of an acyclic ester, methyl benzoate, with 1a afforded triethylsilyl benzoate. O-Silyl-protected amino acids could be obtained by amination of the halosilation products, triethylsilyl omega-bromoalkanoates.

Journal Article↗
PubMed2002

A new synthesis of Neu5Ac from D-glucono-delta-lactone.

A new route to Neu5Ac methyl ester (23) with a readily available sugar D-glucono-delta-lactone as starting material has been developed. A diastereoselective propargylation of alpha-acetamino aldehyde and a subsequent KMnO(4) oxidation of the terminal alkyne served as the key steps.

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PubMed2003

A short olefin metathesis-based route to enantiomerically pure arylated dihydropyrans and alpha, beta-unsaturated delta-valero lactones.

The synthesis of arylated dihydropyrans and unsaturated lactones starting from enantiomerically pure alpha-hydroxy ketones (prepared by an enzyme-catalyzed benzoin condensation) is described. The key steps are a highly diastereoselective addition of vinyl metal compounds under chelate control and a ruthenium-catalyzed ring-closing olefin metathesis reaction. Elucidation of the relative configuration of the final products was achieved by NOE experiments.

Journal Article↗
PubMed2003

Vinylalumination for the synthesis of functionalized allyl alcohols, vinylepoxides, and alpha-alkylidene-beta-hydroxy-gamma-lactones.

A modified hydroalumination protocol for the preparation of [alpha-(ethoxycarbonyl)vinyl]diisobutylaluminum and its beta-methyl or -phenyl analogues was developed. These vinylaluminum reagents react with aldehydes and ketones to provide the corresponding functionalized allyl alcohols in good to excellent yields. Perfluoroalkyl and -aryl carbonyl compounds, alpha-keto esters, alpha-acyl cyanides, and alpha-acetylenic ketones provide the corresponding alpha-hydroxyalkenes in high yields. The allyl alcohol product ratios from the vinylalumination of unsymmetrical alpha-diketones with [alpha-(ethoxycarbonyl)vinyl]diisobutylaluminum and its beta-methyl or -phenyl analogues depend on the steric and electronic environments of the ketones as well as the reagents. The products from the vinylalumination of alpha-bromoaldehydes and -ketones were cyclized with K2CO3 or KF under nonaqueous conditions to provide functionalized vinylepoxides in high yields. Vinylaluminations of keto-protected pyruvaldehyde provided the products, which were converted to alpha-alkylidene-beta-hydroxy-gamma-lactones.

Journal Article↗
PubMed2005

Determination of molecular structure using vibrational circular dichroism spectroscopy: the keto-lactone product of Baeyer-Villiger oxidation of (+)-(1R,5S)-bicyclo[3.3.1]nonane-2,7-dione.

[reaction: see text] The Baeyer-Villiger oxidation of (+)-(1R,5S)-bicyclo[3.3.1]nonane-2,7-dione, 1, can lead to four keto-lactone products, 2a-d. A single isomer is obtained experimentally. We have used IR and VCD spectroscopies to identify the structure of this product. DFT calculations of the IR and VCD spectra of 2a-d show unambiguously that the experimental product is (+)-(1R,6R)-2a, and not the expected product 2b. NMR studies, including comparison of DFT and experimental 1H and 13C spectra, support this conclusion. This work provides the first example of the use of VCD spectroscopy to discriminate between structural isomers of a chiral molecule. The specific rotation of (+)-(1R,6R)-2a, predicted using TDDFT methods, is negative demonstrating that absolute configurations determined from TDDFT calculations of specific rotations are not 100% reliable.

Journal Article↗
PubMed2004

Stereoselective synthesis of pentacarbonyl(3-oxa-2-bicyclo[3.1.0]hexylidene)- and pentacarbonyl(cyclopropylmethoxymethylene)tungsten compounds on the route to cyclopropane-gamma-lactones and -carboxylates.

The diastereoselective synthesis of pentacarbonyl-3-oxa-2-bicyclo[3.1.0]hexylidene- and pentacarbonyl(cyclopropylmethoxymethylene)tungsten compounds 4 and 9 by the reaction of lithiated oxazolinyloxiranes 2 and 8 and Fischer carbene tungsten complexes 3 is described. A mechanism for the formation of 4 and 9 is reported as well as their oxidation to cyclopropane-gamma-lactone 13 and -carboxylate 14.

Journal Article↗
PubMed2004

Dimerization of butenolide structures. A biomimetic approach to the dimeric sesquiterpene lactones (+/-)-biatractylolide and (+/-)-biepiasterolide.

The biomimetic synthesis of the bisesquiterpene lactones (+/-)-biatractylolide 1 and (+/-)-biepiasterolide 2 via dimerization of the captodative stabilized radical 8 is reported. Atractylon 7 has also been shown to be a possible intermediate during the biosynthesis of biatractylolide 1, biepiasterolide 2, atractylolide 3, and hydroxyatractylolide 4.

4-Butyrolactone↗
PubMed1996

Syntheses of (-)-Isocitric Acid Lactone and (-)-Homoisocitric Acid. A New Method of Conversion of Alkynylsilanes into the Alkynyl Thioether and Corresponding Carboxylic Acids.

A simple, stereoselective synthesis of natural isocitric and homoisocitric acids from a common alkynylsilane correlates the stereochemistry of these acids. Starting with dimethyl D-malate dianion, methyl 2-hydroxy-3-carbomethoxy-6-(trimethylsilyl)-5-hexynoate (6a) was prepared with a good stereoselectivity (threo/erythro 90/10). Oxidative cleavage of the triple bond provided isocitric acid lactone (8') in 15% overall yield starting from D-malic acid diester 1. The synthesis of homoisocitric acid relied on a new method of conversion of alkynylsilane to alkynyl thioether, which is converted to the carboxylic acid of the same chain length. Addition of benzenesulfenyl chloride to (trimethylsilyl)alkyne 6b and elimination of trimethylsilyl chloride gave the corresponding thioether 10, which by acid hydrolysis gave homoisocitric acid (11) in a 24% yield from D-malic acid ester. This novel method of conversion of alkynylsilane to the corresponding acid was illustrated with several other alkynyltrimethylsilanes.

Journal Article↗
PubMed1996

Terracinolides A and B, Two Bishomoditerpene Lactones with a Novel Carbon Framework from Euphorbia terracina.

A methanolic extract of Euphorbia terracina L. has been shown to contain two peracylated polyhydroxy terpenoid lactones with a novel C(22) carbon framework. These metabolites, which have been named terracinolides A (1) and B (2), are based on the same parent compound, but differ in the nature of one of the acyl residues. This novel skeletal system is formally derived from the jatrophane framework by addition of a two-carbon fragment on C-17 (jatrophane numbering).

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PubMed1997

Benzotriazole- and 1,2,4-Triazole-Stabilized Allylic Anions: Applications in Syntheses of Functionalized alpha,beta-Unsaturated Ketones, gamma-Lactones, gamma-Lactams, and beta-Substituted Esters.

Deprotonated 1-(benzotriazol-1-yl)-1-ethoxy-2-hexene (7) reacted with alkyl halides, aldehydes, ketones, imines, and alpha,beta-unsaturated esters to give exclusively the alpha-alkylated products 8a-c, 10a,b, 12, 14, 16, and 18a,b, respectively. Without isolation, these products were hydrolyzed under mild conditions to generate the corresponding simple or functionalized alpha,beta-unsaturated ketones 9a-c, 11a,b, 13, 15, 17, and 19a,b. Similar reactions with the phenyl-substituted analog 3-(benzotriazol-1-yl)-3-ethoxy-1-phenyl-1-propene (21) also gave the analogous alpha-products, but they were accompanied by small amount of the gamma-products in most cases. By contrast, deprotonation of the corresponding triazole derivative 29 with butyllithium followed by reactions with alkyl halides, aldehydes, ketones, or imines yielded exclusively gamma-alkylated adducts 32, 34, 36, 38, 40, and 42. Intermediates 32, 34, 36, 38, 40, and 42 were readily converted into beta-substituted esters 33a-c, gamma-lactones 35a,b, 39, 41, and 43, and gamma-lactams 37a-c on hydrolysis.

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