An enantioselective synthesis of (+)-picrasin B, (+)-.DELTA.2-picrasin B, and (+)-quassin from the R-(-) enantiomer of the Wieland-Miescher ketone

Quassia amara L. (Simaroubaceae) leaf tea: Effect of the growing stage and desiccation status on the antimalarial activity of a traditional preparation

“…The most active one contained simalikalactone D (SkD, 49 mg, 0.0095%), while picrasine B (61 mg, 0.012%) was isolated in the less active fraction. NMR spectra were identical to those reported in the literature (SkD: Cabral et al, 1993;Apers et al, 2002;Picrasin B: Handa et al, 1983;Kim et al, 1990).…”

Quassinoids and Other Constituents from Picrasma crenata

“…Four of them show ed identical spectra as described for quassin [11,12], neoquassin (1) [13], p arain [10], and ll-d ih y d ro-12-norneoquassin [12,14], N M R spectra of neoquassin (1) w ere alm ost in accordance w ith literatu re [13], Several proton and carbon nuclei gave rise to pairs of signals. It is th erefo re evident th at b o th the 16a-and 16/?-O H hem iacetal form s are present.…”

Chemoenzymatic resolution of racemic Wieland–Miescher and Hajos–Parrish ketones

“…Bicyclic enones are in the center of interest of many research institutes because they may be transformed to biologically active compounds, such as sesquiterpenoids, quassinoids and steroids (Cheung and Wong 1999;Yoe et al 1995;Kim et al 1990;Grieco et al 1993). Therefore, a number of works concerning Wieland-Miescher (1) or Hajos-Parrish (2) ketones focus on kinetic resolution of racemic mixtures of these compounds, using yeasts (Hioki et al 2000;Fuhshuku et al 2000;Fuhshuku et al 2003) and their isolated enzymes (Shimizu et al 2002) as biocatalysts.…”