Showing papers on "Xanthone published in 1995"

Effect of excitation on the host–guest equilibrium constants of cyclodextrin complexes

Abstract: The equilibrium constants for excited triplet xanthone with cyclodextrins are measured directly by spectroscopically following the decay of triplet xanthone and are shown to be much smaller than those observed for the ground state.

Ruthenium catalyzed regioselective copolymerization of anthrone, fluorenone, or xanthone with α,ω-dienes

Abstract: This paper reports a novel ruthenium catalyzed regioselective copolymerization reaction between anthrone, fluorenone or xanthone and α,ω-dienes such as 1,3-divinyltetramethyldisiloxane and 3,3,6,6-tetramethyl-3,6-disila-1,7-octadiene. This reaction involves the ruthenium catalyzed regioselective Anti-Markovnikov insertion of the carbon-carbon double bonds of the α,ω-dienes into the aromatic carbon-hydrogen bonds which are ortho to the carbonyl group of anthrone, fluorenone or xanthone. Similar ruthenium catalyzed copolymerization reactions between acetophenone and α,ω-dienes [1] have been recently reported as have reactions between acetophenone and alkenes to yield monomeric ortho-alkyl substituted acetophenones [2].

Anti-helicobacter pylori medicine

Abstract: PURPOSE: To obtain a medicine containing a xanthone derivative, etc., having a Hericobacter pylori-resistant action and effective for the therapy of upper alimentary canal diseases such as peptic ulcer, gastritis and stomach cancer. CONSTITUTION: This medicine contains a xanthone derivative of formula I (R1 , R2 are H, methyl), xanthone I of formula II, galtanin of formula III or egonol of formula IV. The medicine is administered at a dose of 0.10-3000mg (preferably 1-1000mg) per day for an adult in one to four portions. The medicine is desirably orally administered but can intravenously be injected. The compounds of formulas I-IV are mainly extracted from the dry rinds of Garcinia mangostana L. (Dicotyledones, Guttiferae), but also obtained by synthetic methods.

Studies on the xanthones from veratrilla baillonii franch iii structure elucidation of a new xanthone glycoside

Abstract: We have reported the isolation of a new xanthone glycoside along with several xanthones from the roots of Veratrilla baillonii Franch.In continuation of our investigations on this folkdrug,from the n-butanol soluble fraction 2,3,4,7-tetramethoxyxanthone-1-O-β-D-xylopyranosyl-(1→6)-β -D-glucopyranoside was isolated as yellow needles,C28H34O16·2H2O,mp 134～135℃.The structure elucidation was mainly accomplished by spectral studies(UV,IR,1HNMR,13CNMR,DEPT,MS).

Xanthones of Halenia corniculata - Part I

Abstract: Three xanthones and their glycosides have been isolated from Halenia corniculata. They were identified as 1-hydroxy-2, 3,5,7-tetramethoxyxanthone (1), 1-hydroxy-2,3,4,5-tetramethoxyxanthone (2), 1-hydroxy-2,3,5-trimethoxyxanthone (3), 2,3,5,7-tetramethoxy-1-0-primeverosyloxyxanthone (4), 2,3,4,5-tetramethoxy-1-0-primeverosyloxyxanthone (5) and 2,3,5-trimethoxy-1-0-primeverosyloxyxanthone (6). Of these, (1) and (4) are new xanthone and xanthone glycoside, while (2), (3), (5) and (6) were isolated for the first time.

Antihelicobacter pylori agent containing xanthone derivative

Abstract: PURPOSE: To obtain the subject medicine, containing a specific xanthone derivative and useful as a preventing and therapeutic agent for diseases in upper gastrointestinal tracts, e.g. peptic ulcer or gastritis regraded as being caused by the infection with Helicobacter pyroli. CONSTITUTION: This medicine contains a xanthone drivative represented by formula I (R1 R4 are each H, a lower alkyl, a lower alkyloxycarbonyl or an acryl), e.g. 3,6-O-dimethyl-α-mangostin. Furthermore, xanthone derivatives represented by formula II and III [R3 and R5 or R4 and R5 , together, are converted into a cyclic form and dC(CH3 )2 -(CH2 )2 ] are preferably used as the derivative and obtained by passing, e.g. α-, β- or γ-mangostin through alkylation for reaction with dimethyl sulfate.

Structure-activity relationship studies in the field of calcium antagonists. Xanthone 1,4-dihydropyridines bearing a 2,3-lactone ring.

Abstract: A series of xanthone 1,4-dihydropyridine derivatives bearing a 2,3-lactone ring and a 2-acetoxymethyl group were prepared. The compounds were evaluated for inotropic, chronotropic and calcium antagonist properties. The introduction of a 2,3-lactone ring improved the negative inotropic activity and selectivity.

Total Synthesis of Novel Xanthone Antibiotics (.+-.)-Cervinomycins A1 and A2.

Abstract: A total synthesis of novel heptacyclic antibiotics cervinomycin A1 1 and A2 2 following a convergent approach is reported. The cornerstone of our strategy was the construction of the central ring D through photochemical electrocyclization. The oxazolo-isoquinolinone fragment (ABC rings) 7 and the xanthone fragment (EFG rings) 8 were assembled through relatively straightforward synthetic protocols and coupled through a Wittig reaction to give 6 and set up the key photocyclization. Our successful approach to 1 and 2 can be readily adapted to the synthesis of analogues of these interesting antibiotics.