Synthesis of porcine brain natriuretic peptide-32 using silver tetrafluoroborate as a new deprotecting reagent of the S-trimethylacetamidomethyl group

Silver tetrafluoroborate (AgBF4) in trifluoroacetic acid (TFA) has been found to cleave the S-trimethylacetamidomethyl (Tacm) group or the S-acetamidomethyl (Acm) group without affecting other functional groups in the peptide chain. Newly isolated porcine brain natriuretic peptide-32 (pBNP-32) was synthesized using AgBF4 and Cys(Tacm) derivatives. The synthetic pBNP-32 had the highest chick rectum relaxant activity among the ANP-BNP families.     

A monoterpene glucoside and three megastigmane glycosides from Juniperus communis var. depressa

A new monoterpene glucoside (1) and three new natural megastigmane glycosides (2-4) were isolated along with a known megastigmane glucoside (5) from twigs with leaves of Juniperus communis var. depressa (Cupressaceae) collected in Oregon, U.S.A., and their structures were determined on the basis of spectral and chemical evidence. In addition, the antibacterial activities of the isolated components against Helicobacter pylori were also investigated.     

Regioselective oxidative coupling of 4-hydroxystilbenes: synthesis of resveratrol and epsilon-viniferin (E)-dehydrodimers

Treatment of 5-[2-(4-hydroxyphenyl)vinyl]benzene-1,3-diol (resveratrol) with an equimolar amount of silver(I) acetate in dry MeOH at 50 degrees C for 1 h followed by chromatographic purification with a short silica gel column allowed the isolation of its (E)-dehydrodimer, 5-[5-[2-(3,5-dihydroxyphenyl)vinyl]-2-(4-hydroxyphenyl)-2,3-dihydrobenzofuran-3-yl]benzene-1,3-diol, as a racemic mixture in high yield. The present method was applicable to the oxidative dimerization of 4-hydroxystilbenes such as trans-styrylphenol and 5-[6-hydroxy-2-(4-hydroxyphenyl)-4-[2-(4-hydroxyphenyl)vinyl]-2,3-dihydrobenzofuran-3-yl]benzene-1,3-diol (epsilon-viniferin) leading to the corresponding 2-(4-hydroxyphenyl)-2,3-dihydrobenzofurans possessing various types of biological activities.     

Selective metal sorption on cross-linked poly(vinylpyridine) resins

The sorption behaviour of several metal ions on five kinds of poly(4- or 2-vinylpyridine) resins, cross-linked with divinylbenzene, and with different surface properties, are examined. All the resins proposed sorb some metal ions effectively in a similar manner by anion-exchange, while the sorption of metal ions by complex formation with the pyridine moiety is strongly affected by the surface properties of the resins. A macroreticular poly(4-vinylpyridine) resin shows high affinity for copper and nickel ions in acetate buffer. Sodium chloride and/or methanol added to the working solutions influence the sorption capacities for metal ions. This resin was applied to the separation of copper/cobalt and nickel/cobalt and the concentration of copper from sea-water by a column operation.     

A pair of new atropisomeric cupressuflavone glucosides isolated from Juniperus communis var. depressa

A pair of new atropisomers, (M)- and (P)-cupressuflavone 4′-O-β-d-glucoside, were isolated from Juniperus communis var. depressa, and their absolute structures and axial configurations were determined using 2D NMR and circular dichroism. These are the first reported stable (M)- and (P)-isomers of cupressuflavone glucosides isolated from natural sources.     

Occurrence of Stilbene Glucosides in Upuna borneensis

Four new stilbene glucosides, upunosides A ( 1 ), B ( 5 ), C ( 6 ), and D ( 7 ), were isolated from the stem of Upuna borneensis (Dipterocarpaceae) together with the three known glucosides 3, 4 , and 8 . Upunoside A ( 1 ) is the first natural instance of a glucoside of a resveratrol pentamer, and its aglycone has a dibenzo‐fused bicyclo[5.3.0]octadiene and two dihydrobenzofuran moieties. The relative structure of the aglycone was determined by spectral analysis including 1D and 2D NMR experiments.     

Allergy-preventive flavonoids from Xanthorrhoea hastilis

Allergy-preventive activity was demonstrated for an extract of resins from Xanthorrhoea hastilis R. BR. in a search for allergy-preventive substances from natural sources. By bioassay-directed fractionation of this plant extract, a new flavanone, 3',5'-dihydroxy-7,4'-dimethoxyflavanone (1), and two new chalcones, 3,5,2'-trihydroxy-4,4'-dimethoxychalcone (2) and 5,2'-dihydroxy-3,4,4'-trimethoxychalcone (3), were isolated together with five known compounds, 5'-hydroxy-7,3',4'-trimethoxyflavanone (4), 3'-hydroxy-7,4'-dimethoxyflavanone (5), liquiritigenin 7-methyl ether (6), 4,2'-dihydroxy-4'-methoxychalcone (7) and sakuranetin (8). The structures of 1, 2 and 3 were elucidated by spectroscopic methods. All of these compounds showed allergy-preventive effects.     

Absolute structures of C-glucosides of resveratrol oligomers from Shorea uliginosa

Two C-glucosides of resveratrol dimers (uliginoside A (1) and hemsleyanoloside B (2)) consisting of enantiomeric aglycones and two C-glucosides of resveratrol trimers (uliginosides B (3) and C (4)) consisting of diastereomeric aglycones were isolated from Shorea uliginosa (Dipterocarpaceae). These structures were elucidated by spectroscopic analysis including NMR experiments, and their absolute configurations were determined based on circular dichroism data. Resveratrol oligomers of C-glucosides with a 1,2-diaryldihydrobenzofuran ring are produced with specific biogenetic routes.     

The multi-configuration Dirac-Fock calculation of the low-lying levels of Sm

The excitation energies and hyper-fine structure constants of the low-lying levels of Sm atom are calculated using the multi-configuration Dirac-Fock (MCDF) method. The results show that the excitation energies of the ground state multiplets can be calculated accurately using a small orbital set but the higher levels need larger orbital sets. Similar inference can also be drawn from the discrepancy between the calculated values of the hyper-fine constants and the experimental data. A sequence of MCDF calculation demonstrates the effect of the MCDF potential on the orbitals. Among the rare earth atoms Sm is a promising candidate for discrete symmetry violation experiments in atoms. This makes accurate theoretical calculations necessary since parameters in particle physics can be derived by combining the experimental results with the theoretical results. And these could be a probe for the physics beyond the standard model. Received 10 October 2000 and Received in final form 23 January 2001