- Glycolipid ester-type heterodimers from Ipomoea tyrianthina and their pharmacological activity
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Tyrianthins A (1) and B (2), two new partially acylated glycolipid ester-type heterodimers were isolated from Ipomoea tyrianthina. Scammonic acid A was determined as the glycosidic acid in both monomeric units. Tyrianthin A (1) (IC50 0.24 ± 0.0
- Leon-Rivera, Ismael,Miron-Lopez, Gumersindo,Estrada-Soto, Samuel,Aguirre-Crespo, Francisco,Gutierrez, Maria del Carmen,Molina-Salinas, Gloria Maria,Hurtado, Gerardo,Navarrete-Vazquez, Gabriel,Montiel, Elizur
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experimental part
p. 4652 - 4656
(2010/04/28)
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- New Routes to Chiral Evans Auxiliaries by Enzymatic Desymmetrisation and Resolution Strategies
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This paper describes how enantiomerically enriched Evans auxiliaries can be successfully prepared by either an enzymatic desymmetrisation strategy or an asymmetric synthesis using racemic auxiliaries and an enzymatic resolution. Desymmetrisation of N-Boc-protected serinol has been achieved in good yield and high enantiomeric excess using porcine pancreas lipase. This has been exploited in different ways to prepare enantiomerically enriched (4R)- and (4S)-substituted 2-oxazolidinones. In another approach to asymmetric synthesis, starting from a racemic Evans auxiliary, by means of a diastereoselective aldol reaction coupled with a lipase-catalysed resolution, we achieved the preparation of enantiomerically enriched β-hydroxy acids and enantiomerically enriched 2-oxazolidinones.
- Neri, Claudia,Williams, Jonathan M. J.
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p. 835 - 848
(2007/10/03)
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- Novel coumarin and chromene compounds and methods of preparation and use thereof for treating or preventing viral infections
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The present invention relates to methods of preparation and use of coumarin and chromene compounds for treating or preventing viral infections.
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- Methods for preparing antiviral calanolide compounds
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The present invention relates to methods for preparing 2,2-dimethyl-5-acyloxy-10-propyl-2H,8H-benzo[1,2-b:3,4-b′]dipyran-8-one (5) and 2,2-dimethyl-5-hydroxy-10-propyl-2H,8H-benzo[1,2-b:3,4-b′]dipyran-8-one (6) and their use as intermediates for the synthesis of antiviral calanolide compounds. For example, Fries rearrangement on compound 5 or Friedel-Crafts reaction on 6, yields intermediate 2,2-dimethyl-5-hydroxy-6-propionyl-10-propyl-2H,8H-benzo[1,2-b:3,4-b′]dipyran-8-one (4), which, in turn, can be converted to (+)-calanolide A and (?)-calanolide B. The coupling of compound 6 with the appropriate chiral molecule under Mitsunobu or nucleophilic displacement leads to the asymmetric synthesis of antiviral calanolide compounds.
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- Methods for preparing antiviral calanolide compounds
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The present invention relates to methods for preparing 2,2-dimethyl-5-acyloxy-10-propyl-2H,8H-benzo[ 1,2-b:3,4-b ′]dipyran-8-one (5) and 2,2-dimethyl-5-hydroxy- 10-propyl-2H,8H-benzo[1,2-b:3,4-b ′]dipyran-8-one (6) and their use as intermediates for the synthesis of antiviral calanolide compounds. For example, Fries rearrangement on compound 5 or Friedel-Crafts reaction on 6, yields intermediate 2,2-dimethyl-5-hydroxy-6-propionyl-10-propyl-2H,8H-benzo[1,2-b:3,4-b′]dipyran-8-one (4), which, in turn, can be converted to (+)-calanolide A and (?)-calanolide B. The coupling of compound 6 with the appropriate chiral molecule under Mitsunobu or nucleophilic displacement leads to the asymmetric synthesis of antiviral calanolide compounds.
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- CHIRAL PROPIONATE ENOLATE EQUIVALENTS FOR THE STEREOSELECTIVE SYNTHESIS OF THREO- OR ERYTHRO-α-METHYL-β-HYDROXY ACIDS.
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The aluminium and copper enolates derived from (n5-C5H5)Fe(CO)(PPh3)COCH2CH3 are chiral propionate enolate equivalents which on reaction with aldehydes (RCHO, R=Me, Et, iPr, tBu) provide stereoselective sytheses of threo-
- Davies, Stephen G.,Dordor-Hedgecock, Isabelle M.,Warner, Peter
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p. 2125 - 2128
(2007/10/02)
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- STEREOSELECTIVE REDUCTION OF 3-OXO AMIDES WITH ZINC BOROHYDRIDE
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2-Alkyl-3-oxo amides were reduced to the corresponding syn-2-alkyl-3-hydroxy amides with high stereoselectivity by zinc borohydride.
- Ito, Yoshio,Yamaguchi, Masaru
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p. 5385 - 5386
(2007/10/02)
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- Methods for the Stereoselective Cis Cyanohydroxylation and Carboxyhydroxylation of Olefins
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Two valuable reagents for the cis-specific vicinal cyanohydroxylation and carboxyhydroxylation of olefins are described.The cyanohydroxylation process is based on the decarboxylative ring opening of 3-carboxyisoxazolines prepared by the cycloaddition reaction of carbethoxyformonitrile oxide with various alkenes.Fragmentation of the isoxazolines prepared from cis- and trans-2-butene has been found to occur without any crossover in stereochemistry.The carboxyhydroxylation process begins with the dipolar cycloaddition reaction of the nitrile oxide derived from thetetrahydropyranyl ether derivative of 2-nitroethanol.Deprotection, hydrogenation, and oxitative cleavage of the derived dihydroxy ketone yield the stereochemcally pure β-hydroxy carboxylic acid.
- Kozikowski, Alan P.,Adamczyk, Maciej
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p. 366 - 372
(2007/10/02)
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