Search results for "Epimer"
showing 10 items of 41 documents
Inositols in the ovaries: activities and potential therapeutic applications.
2022
Introduction: Myo-inositol (MI) and D-chiro-inositol (DCI) play a key role in ovarian physiology, as they are second messengers of insulin and gonadotropins. Ex-vivo and in-vitro experiments demonstrate that both isomers are deeply involved in steroid biosynthesis, and that reduced MI-to-DCI ratios are associated with pathological imbalance of sex hormones. Areas covered: This expert opinion provides an overview of the physiological distribution of MI and DCI in the ovarian tissues, and a thorough insight of their involvement into ovarian steroidogenesis. Insulin resistance and compensatory hyperinsulinemia dramatically reduce the MI-to-DCI ratio in the ovaries, leading to gynecological dis…
Neoclerodane Diterpenoids from Teucrium maghrebinum
2000
Eight neoclerodane diterpenoids were identified in the extract of the aerial parts of Teucrium maghrebinum. Three of these, 12-epi-teucjaponin A (1), 12-epi-montanin D (2), and 12-epi-montanin B (3), are new natural products, whereas five, teucjaponin A, montanin D, 19-deacetylteuscorodol, teusalvin C (4), and montanin B, are already known. These eight compounds form four pairs of epimers at carbon C-12.
Photoinduced functionalization of diterpenes: photochemical behaviour of grandifloric acid in methanol and acetonitrile
2004
Abstract Irradiation of grandiflorolic acid (11) at λ=254 nm in acetonitrile gave the two epimers 13 and 14 through a photodecarboxylation reaction of the carboxylic group on C-4. Irradiation of compound 11 in methanol at λ=254 nm provided the transformation of the C-20 angular methyl into a carbomethoxymethyl group. In this case, unlike compounds 13 and 14, only one of the two possible isomers (15) was obtained (equatorial methyl at C-4). A mechanistic approach of this reaction in discussed, and the role of mutual stereochemistry between C-20 methyl and C-19 carboxylic group in determining the course of the reaction is pointed out.
Systematic conformational search analysis of the SRR and RRR epimers of 7-hydroxymatairesinol
2009
An extensive and systematic conformational search was performed on the two epimers of the natural lignan 7-hydroxymatairesinol (HMR), by means of a home-made Systematic Conformational Search Analysis (SCSA) code, designed to select more and more stable conformers through sequential geometry optimization of trial structures at increasing levels of calculation theory. In the present case, the starting molecular structures were selected by the semi-empirical AM1 method and filtered – i.e. decreased in number by choosing the more stable species – on the basis of their energy calculated by the HF method and the 6-31G(d) basis set. The geometries obtained were further refined by performing densit…
Non-Classical Transformation of Benzendiazonium Hydrogen Sulfates. Access to 1,3-Dimethylisochromeno[4,3-c]pyrazol-5(1H)-one, a Potential Benzodiazep…
2013
The compound 2-((1,3-dimethyl-1H-pyrazol-5-yl)(methyl)carbamoyl)benzene-diazonium hydrogen sulfate (10) was reacted with copper sulfate and sodium chloride, in the presence of ascorbic acid as reducing agent, to afford a mixture of the chlorinated epimers 4′-chloro-2,2′,5′-trimethyl-2′,4′-dihydrospiro[isoindoline-1,3′-pyrazol]-3-one (18) and (19), the epimers 4′-hydroxy-2,2′,5′-trimethyl-2′,4′-dihydrospiro[isoindoline-1,3′-pyrazol]-3-one (20) and (21), and N-(1,3-dimethyl-1H-pyrazol-5-yl)benzamide (22). Under the foregoing conditions, diazonium salt 10 affords neither the 2-chloro-N-(1,3-dimethyl-1H-pyrazol-5-yl)-N-methylbenzamide (23) nor the tricyclic derivative 24, the classical products…
Atractyligenin chemistry. Part 4: Synthesis of the 15β-ol epimer of atractyligenin
1996
The oxidation with PCC of atractyligenin 3, the aglicone of the toxic glycoside 1 isolated from Atractylis gummifera L., led to the 15-oxo-derivative 6, together with a small amount of 2,15-dioxoderivative 5, with a selective oxidation of the allylic 15-OH group of the molecule. Further reduction with NaBH4 and KOH hydrolysis gave stereoselectively the 15β-ol epimer of atractiligenin 9.
Synthesis of (−)-auricularic acid and its C-4 epimer the absolute configuration of auricularic acid
1991
Abstract A synthesis of (−)-auricularic acid (2a) starting from methyl (+)-13-oxo- podocarp-8(14)-en-19-oate (3a) and a synthesis of its C-4 epimer (2b) starting from methyl (+)-13-oxopodocarp-8(14)-en-18-oate (3b) are described. The absolute configuration of natural auricularic acid is stablished as (4R, 5S, 8S, 9R, 10S, 14S).
Stereostructural revision of auricularic acid synthesis of 4-epi-auricularic acid
1989
Abstract Cleistanth-13,15-dien-18-oic acid (1) has been synthesised from methyl 13-keto-podocarp-8(14)-en-18-oate (3). It is demonstrated that auricularic acid is an epimer at C-4 of 1, so it must be reformulated as cleistanth-13,15-dien-19-oic acid (2).
Sesquiterpene lactones from Centaurea alba and C. conifera
1995
Abstract The aerial parts of Centaurea alba yielded five know germacranolides: salonitenolide, 11β, 13-dihydrosalonitenolide, salonitenolide 8- O -(4′-acetoxy-5′-hydroxy)-angelate, cnicin 4′-O-acetate and cnicin. The aerial parts of C. conifera yielded loliolide, 1β,6α-dihydroxy-4(15)-eudesmene, chlorojanerin, chlorohyssopifolin A (centaurepensin) and its C-17 epimer. The latter compound is described for the first time.
ChemInform Abstract: Synthesis of (-)-Auricularic Acid and its C-4 Epimer. The Absolute Configuration of Auricularic Acid.
2010
Abstract A synthesis of (−)-auricularic acid (2a) starting from methyl (+)-13-oxo- podocarp-8(14)-en-19-oate (3a) and a synthesis of its C-4 epimer (2b) starting from methyl (+)-13-oxopodocarp-8(14)-en-18-oate (3b) are described. The absolute configuration of natural auricularic acid is stablished as (4R, 5S, 8S, 9R, 10S, 14S).