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At least 721 records · Page 40Linked to original sources
PubMed2004

Corymbiferan lactones from Penicillium hordei: stimulation of novel phenolic metabolites using plant tissue media.

Cultivation of a strain of Penicillium hordei on macerated tulip tissue agar resulted in the stimulated production of a series of four novel hydroxymethyl naphthalene carboxylic acid lactones from the fungus. The naphthalene derivatives were isolated using a combination of vacuum liquid chromatography and preparative HPLC. Their structures were determined by 1D and 2D NMR techniques in conjunction with high-resolution electrospray mass spectrometry (HRESIMS). These metabolites were given the trivial names corymbiferan lactones A-D (1-4).

Chromatography, High Pressure Liquid↗
PubMed2005

Vittatalactone, a beta-lactone from the striped cucumber beetle, Acalymma vittatum.

A novel beta-lactone, vittatalactone (1), was isolated from collections of airborne volatile compounds from feeding male striped cucumber beetles, Acalymma vittatum. The structure of 1 was determined to be (3R,4R)-3-methyl-4-(1,3,5,7-tetramethyloctyl)oxetan-2-one by microderivatization, GC-MS, and NMR studies. The absolute configurations at C-2 and C-3 on the beta-lactone ring were assigned by use of the modified Mosher method, applied to the beta-hydroxy acid methyl ester resulting from methanolysis of 1. Biological activity of 1, possibly as an aggregation pheromone for A. vittatum, was indicated by electrophysiological studies using beetle antennae and by the production of 1 by feeding male, and not female, beetles.

Animals↗
PubMed2002

Mild and chemoselective synthesis of lactones from diols using a novel metal-ligand bifunctional catalyst.

[reaction: see text] A novel amino alcohol-based Ir bifunctional complex acts as an efficient catalyst for oxidative lactonization of 1,4- or 1,5-diols with a substrate-to-catalyst molar ratio of 200-1000 in acetone or butanone. The reaction proceeds with broad functional group tolerance to give lactone in high yield at room temperature. The catalyst precursor Cp*IrCl[OCH(2)C(C(6)H(5))(2)NH(2)] is isolated and characterized by a single-crystal X-ray analysis.

Catalysis↗
PubMed2003

On the structure of passifloricin A: asymmetric synthesis of the delta-lactones of (2Z,5S,7R,9S,11S)- and (2Z,5R,7R,9S,11S)tetrahydroxyhexacos-2-enoic acid.

Stereoselective syntheses of the delta-lactone of (2Z,5S,7R,9S,11S)-tetrahydroxyhexacos-2-enoic acid, the structure reported for passifloricin A, and of its (5R)-epimer are described. The creation of all stereogenic centers relied upon Brown's asymmetric allylation methodology. The lactone ring was created via ring-closing metathesis. The NMR data of both synthetic products, however, were different from those of the natural product. The published structure of passifloricin A is thus erroneous and will require further synthetic work to be unambiguously assigned. [structure: see text]

Cyclization↗
PubMed2005

Novel lactonization of ethenetricarboxylate derivatives: intermolecular trapping of alkenes.

A novel cyclization of 1,1-diethyl 2-tert-butyl ethenetricarboxylate (1a) in the presence of a Lewis acid afforded a 5,5-dimethyl-gamma-lactone derivative 2a. The reaction process has been shown to arise from formation by trapping of isobutylene generated in situ. Lewis acid-promoted intermolecular reactions of 1,1-diethyl 2-hydrogen ethenetricarboxylate (5) and various alkenes to afford highly functionalized gamma-lactones were also developed. [reaction: see text]

Alkenes↗
PubMed2005

Preparation of 1-thio uronic acid lactones and their use in oligosaccharide synthesis.

The chemo- and regioselective TEMPO/BAIB-mediated oxidation of 2,6- and 3,6-dihydroxy 1-thio glycopyranosides to the corresponding 1-thio uronic acid lactones is described. These locked 1-thio glycuronides can directly be used as donors in glycosidation reactions using the Ph(2)SO/Tf(2)O reagent system. Alternatively, selective opening of the lactone bridge liberates a hydroxyl function for ensuing glycosylations.

Lactones↗
PubMed2006

Utilization of a 1,2-dioxine for the synthesis of the four possible stereoisomers of oak lactone.

[reaction: see text]. The natural products cis- and trans-oak lactone (1) have been prepared, along with their enantiomeric counterparts, from furanone 12, which was itself prepared from racemic 1,2-dioxine 9 and a chiral malonate diester. The key steps in the synthesis of 1 are the use of the malonate diester as a chromatographic resolving agent and the decarboxylation of 13, which can be directed to give either the cis- or trans-product. This leads to all four possible oak lactone stereoisomers from a common intermediate.

Biological Products↗
PubMed2006

Practical beta-lactone synthesis: epoxide carbonylation at 1 atm.

[reaction: see text] A readily prepared bimetallic catalyst is capable of effecting epoxide carbonylation to produce beta-lactones at substantially lower CO pressures than previously reported catalyst systems. A functionally diverse array of beta-lactones is produced in excellent yields at CO pressures as low as 1 atm. This procedure allows for epoxide carbonylation on a multigram scale without the requirement of specialized, high-pressure equipment.

Catalysis↗
PubMed2006

The first total synthesis of (-) and (+)-2-hydroxy-24-oxooctacosanolide using an effective lactonization.

[structure: see text] An effective method for the total synthesis of 2-hydroxy-24-oxooctacosanolide, a defensive salivary secretion of the African termite Pseudacanthotermes spiniger, has been developed. The key lactonization to form a 29-membered ring lactone core is performed using 2-methyl-6-nitrobenzoic anhydride with a catalytic amount of 4-(dimethylamino)pyridine N-oxide.

Animals↗
PubMed1999

Novel strategies to construct the gamma-hydroxy lactone moiety of the CP molecules. Synthesis of the CP-225,917 core skeleton.

[formula: see text] The array of challenging structural lineaments embodied in the CP molecules (1 and 2, Figure 1) offers synthetic chemists uncharted realms of exploration and discovery. In this communication, we focus on the chemical hurdies posed by the gamma-hydroxy lactone moiety of these exciting targets. Thus, the examination of the general reactivity of these systems, the development of a novel tandem oxidation sequence to construct the gamma-hydroxy lactone moiety, and the successful construction of the complete polycyclic core of 2 (compound 28, Scheme 5) is enumerated within.

Enzyme Inhibitors↗
PubMedDate not supplied

Bihaptens with 5- and 6-methyl-substituted alkylcatechols and methylene lactone functional groups: tools for hapten (allergen or tolerogen)-protein interaction studies.

In order to investigate hapten-protein interactions in vivo, potential skin sensitizers 1-3, with two different haptenic ends, (a) a catechol, a 5-methylcatechol, and a 6-methylcatechol respectively, and (b) an alpha-methylene-gamma-butyrolactone moiety, separated by a straight 10-carbon chain, have been prepared and used to sensitize guinea pigs. Related "monohapten lactones" 19-21, containing an electrophilic alpha-methylene-gamma-butyrolactone moiety connected to the protected catechol structures, and "monohapten catechols" 25-27, containing a reduced alpha-methyl-gamma-butyrolactone linked to the catechol, also have been prepared. Bihaptens 1 and 2 which were found to have very close biological activities appear to react with proteins through the catechol ring, indicating a low importance of the C-6 position in the binding of catechols with amino acids. In contrast, bihapten 3 was found to react through both the catechol and lactone ring. The influence of amino and thiol binding sites on the biological activity (allergy or tolerance) as well as the influence of the sensitizing method are discussed.

Allergens↗
PubMed1990

Sesquiterpene lactones and other constituents from a cytotoxic extract of Michelia floribunda.

The pentane and CHCl3 fractions of a crude extract of Michelia floribunda exhibited cytotoxic activity when tested in KB and P388 tumor cell cultures. Repeated chromatography led to the isolation of three cytotoxic sesquiterpene lactones (costunolide, parthenolide, and santamarine) and a cytotoxic isoquinoline alkaloid (liriodenine). Inactive sesquiterpene lactones obtained during the course of this study included dihydroparthenolide and two new glucosides of dihydrotamaulipin A and dihydroreynosin (1 and 2). The structures of these new compounds were determined through interpretation of their spectroscopic data including 2D-NMR spectroscopy. Syringin was also isolated from the extract.

Animals↗
PubMed2003

Effects of lycorine on growth and effects of L-galactonic acid-gamma-lactone on ascorbic acid biosynthesis in strains of Cryptococcus laurentii isolated from Narcissus pseudonarcissus roots and bulbs.

The alkaloid lycorine, which is considered to inhibit the last step in ascorbic acid biosynthesis, is produced by Narcissus pseudonarcissus. The growth of two strains (C1 and C3) of Cryptococcus laurentii isolated from root tips of N. pseudonarcissus is inhibited by lycorine, as is the in vivo production of ascorbic acid from L-galactonic acid-gamma-lactone. In contrast, C. laurentii strain C4, isolated from the lycorine-containing bracts of the bulb, was not inhibited by lycorine and did not contain ascorbic acid when cultivated with or without L-galactonic acid-gamma-lactone.

Amaryllidaceae Alkaloids↗
PubMed2005

Ring fission of chiral cyclic acetals plus intramolecular [4 + 2] cycloaddition: a sequential access to medium-size lactones. Application to the synthesis of carbasugars.

A set of alpha,beta-unsaturated cyclic acetals were reacted with t-butyllithium in THF. A conjugate elimination took place, triggering a ketal ring cleavage when two eq. of TMEDA were added to the medium. The lithium alcoholate thus obtained could be trapped in situ by 2,2,2-trifluoroethyl acrylate. The resulting acryloyl (1Z,3E)-dienyl ether was then submitted to an intramolecular Diels-Alder cycloaddition under high pressure (12 kbar, 50 degrees C). Depending on the structure of the linkage between the diene and the acrylate, the expected ("fused") lactones were obtained with total endo- or exo-selectivities and high to complete diastereoselectivities. A remarkable inversion of selectivity, from endo to exo, with respect to the stereochemical elements of the tether could be observed in these cases. A five step diastereoselective transformation of two of the resulting nine-membered ring lactones into modified carbasugars was finally achieved in 23% overall yield.

Acetals↗