1.Time-lapse STM studies of diastereomeric cinchona alkaloids on platinum metals.
Wahl M;von Arx M;Jung TA;Baiker A J Phys Chem B. 2006 Nov 2;110(43):21777-82.
The adsorption of cinchonidine (CD) and cinchonine (CN) on Pt(111) and Pd(111) single crystals has been investigated by means of scanning tunneling microscopy (STM) in an ultrahigh vacuum system. In time-lapse series the mobilities of different adsorption species have been determined on a single molecule basis and with varying hydrogen background pressures in the system. The diastereomeric cinchona alkaloids, CD and CN, which are widely used as chiral modifiers of platinum group metals in catalytic enantioselective hydrogenation, showed similar adsorption modes and diffusion behavior on Pt(111), except that the flatly adsorbed CN molecules which were free (not in a dimer/cluster) were significantly more mobile than their CD analogues. CD adsorbed on Pd(111) showed similar adsorption modes as observed on Pt(111) but at considerably higher mobility of the flatly absorbed species already in the low-pressure region. The observed adsorption behaviors are discussed in the context of independent ATR-IR measurements and theoretical calculations.
2.Asymmetric Synthesis of Axially Chiral Benzocarbazole Derivatives Based on Catalytic Enantioselective Hydroarylation of Alkynes.
Arae S;Beppu S;Kawatsu T;Igawa K;Tomooka K;Irie R Org Lett. 2018 Aug 17;20(16):4796-4800. doi: 10.1021/acs.orglett.8b01945. Epub 2018 Aug 1.
A new synthetic approach to novel axially chiral benzocarbazole derivatives based on the highly enantioselective intramolecular hydroarylation (94-96% ee) of linked alkyne-indole systems by using the prevalent chiral base catalyst, cinchonidine or cinchonine, under unprecedented transition-metal-free conditions is described. The process is considered to involve chiral base catalysis for enantioselective transformation of the alkyne part to a reaction intermediate with an axially chiral vinylidene o-quinone methide (VQM) functionality, which subsequently effects stereospecific cyclization with the tethered indole moiety.
3.Development of a generic micellar electrokinetic chromatography method for the separation of 15 antimalarial drugs as a tool to detect medicine counterfeiting.
Lamalle C;Djang'Eing'A Marini R;Debrus B;Lebrun P;Crommen J;Hubert P;Servais AC;Fillet M Electrophoresis. 2012 Jun;33(11):1669-78. doi: 10.1002/elps.201100621.
Since antimalarial drugs counterfeiting is dramatically present on the African market, the development of simple analytical methods for their quality control is of great importance. This work consists in the CE analysis of 15 antimalarials (artesunate, artemether, amodiaquine, chloroquine, piperaquine, primaquine, quinine, cinchonine, mefloquine, halofantrine, sulfadoxine, sulfalen, atovaquone, proguanil, and pyrimethamine). Since all these molecules cannot be ionized at the same pH, MEKC was preferred because it also allows separation of neutral compounds. Preliminary experiments were first carried out to select the most crucial factors affecting the antimalarials separation. Several conditions were tested and four parameters as well as their investigation domain were chosen: pH (5-10), SDS concentration (20-90 mM), ACN proportion (10-40%), and temperature (20-35°C). Then, the experimental design methodology was used and a central composite design was selected.
