34425-60-0Relevant articles and documents
Synthesis and bioactivities of naturally occurring anthraquinones: Isochrysophanol, isozyganein, ω-hydroxyisochrysophanol and morindaparvin
Zaidi, Javed H.,Naeem, Fazal,Iqbal, Rashid,Choudhary, Mohammed Iqbal,Khan, Khalid Mohammed,Perveen, Shahnaz,Ali Shah, Syed T.,Hayat, Safdar,Voelter, Wolfgang
, p. 689 - 696 (2007/10/03)
Isochrysophanol, isozyganein, ω-hydroxyisochrysophanol, and morindaparvin are naturally occurring substituted anthraquinones. We report the synthesis of these compounds as well as selected biological activities.
Substituent Effects upon Peak Potentials and Reductive Cleavage Rate Constants of Hydroxy- and Methoxy-Substituted 9,10-Anthraquinones in 50percent Aqueous CH3CN: Do They Correlate?
Blankespoor, Ronald L.,Kosters, Elise L.,Post, Alan J.,VanMeurs, Derek P.
, p. 1609 - 1614 (2007/10/02)
A variety of hydroxy- and methoxy-substituted 2-(acetoxymethyl)-9,10-anthraquinones (2a-7a) were reduced electrochemically and with dithionite (S2O42-) in 50percent aqueous CH3CN buffers over a wide pH range.Good to excellent yields of their corresponding reductive cleavage products, the substituted 2-methyl-9,10-anthraquinones 2b-7b, were obtained from most of these anthrachinone acetates, but only at higher pH.Rate constants for the reaction of 2-(acetoxymethyl)-9,10-anthraquinone (1a) with excess dithionite ranged from 1.0 x 10E-4 s-1 at pH values less than 7 to 4.0 x 10E- 4 s-1 at a pH of 10, demonstrating that loss of acetate occurs in the rate-determining step and that cleavage occurs slower via the anthrahydroquinone of 1a than the conjugate base of the anthrahydroquinone.Substituent effects upon the reductive cleavage process were determined by measuring rate constants for those acetates that react cleanly with dithionite at pH 8.These effects, which are rationalized on the basis of resonance theory and intramolecular H bonding, correlate fairly well with the peak potentials (Ep) of the reductive cleavage products of these acetates.Thus, electron-donating substituents on an anthraquinone acetate not only make it more difficult to reduce resulting in a more negative Ep but also enhance the rate of acetate cleavage in the corresponding anthrahydroquinone.
REACTIONS OF KETENE ACETALS-14; THE USE OF SIMPLE MIXED VINYLKETENE ACETALS IN THE ANNULATION OF QUINONES
Savard, Jacques,Brassard, Paul
, p. 3455 - 3464 (2007/10/02)
α,β- and β,γ-unsaturated esters can be converted by strong base and chlorotrimethylsilane to the corresponding mixed vinylketene acetals which are shown to be particularly useful and generally applicable reagents for the regiospecific annulation of halogenoquinones.The reaction proceeds readily with a variety of substrates including benzoquinones.
