Chemical Composition of and Inhibition of Angiotensin-Converting Enzyme by Senecio samnitum huet

Abstract Extracts of Senecio samnitum Huet and derived methyl ester of chlorogenic acid have been shown to inhibit angiotensin-converting enzyme (ACE) by using an in vitro bioassay based on the enzymatic cleavage of the chromophore-fluorophore labeled substrate dansyltriglycine into dansylglycine, which is quantitatively measured by high-performance liquid chromatography (HPLC). GC=MS and NMR identified compounds present within the studied S. samnitum extracts. The most effective fraction was obtained in ethyl acetate, which gave 52.56 AE 0.23% (SD) inhibition at 300 mg=ml. The major constituent of this fraction, the methyl ester of chlorogenic acid, showed significant ACE inhibition of 56.78 AE 0.25% at a concentration of 82.5 mg=ml

Stabilizing Effect by Geminal Dioxy Substitution and Anomeric Effect in 3,6-Dihydro-6-Methoxy-1,2-Oxathiin 2-Oxides

The hetero-Diels-Alder addition Of SO2 to (E)-hexa-1,3-diene (4) gives first 6-ethyl-3,6-dihydro-1,2-oxathiin 2-oxide (= 6-ethylsultine) with the Et group occupying a pseudoaxial position, and then the more stable stereoisomer 6 with the Et substituent in a pseudoequatorial position. The SO2 additions to 1-methoxybuta-1,3-diene (7) and to 1-methoxy-3-[(trimethylsilyl)oxy]buta-1,3-diene (8) give the 6-methoxysultines 9 and 10, respectively, with the MeO groups in pseudoaxial positions and which do not equilibrate with sultines having pseudoequatorial MeO substituents (anomeric effect). A lower limit of DELTADELTAG = 3.9 kcal/mol was evaluated at -60-degrees for the stabilizing effect arising from the geminal vicinity of a MeO and sulfinate moiety in 3,6-dihydro-6-methoxy-4-[(trimethylsilyl)oxy]-1,2-oxathiin 2-oxide

Site Selectivity and Regioselectivity of the Hetero-Diels-Alder and Cheletropic Additions of Sulfur-Dioxide to a 2,3,6,7-Tetramethylidenebicyclo[3.2.1]Octane Derivative

At -55-degrees-C SO2 adds to 4-[(tert-butyl)dimethylsilyloxy]-1-methoxy-2,3,6,7-tetramethylidenebicyc lo[3.2.1]octane reversibly and selectively onto the s-cis-butadiene moiety at C(2), C(3) giving a single regioisomeric sultine. At -45-degrees-C the cheletropic addition of SO2 occurs selectively giving the monosulfolene attached at C(2), C(3)

New carbon-carbon bond formation through oxyallylation of enoxysilanes with sulfur dioxide adduct of 1-methoxybutadiene. Stereoselective synthesis of (Z)-4-methoxy-6-oxoalk-2-enyl methyl sulfones

Mixtures of 1-methoxybutadiene, trimethylsilyl enol ethers, SO2 and a Lewis acid catalyst generate trimethylsilyl (Z)-4-methoxy-6-oxoalk-2-enesulfinates that can be converted into 4-methoxy-6-oxoalk-2-enyl methyl sulfones and 5-alkyl-4-methoxy-6-oxoalk-2-enyl methyl sulfones with 100% (Z) selectivity and good syn diastereoselectivity for the 5-alkyl and 4-methoxy substituents. (C) 1997 Elsevier Science Ltd