Ball milling - a new concept for predicting degradation profiles in active pharmaceutical ingredients

A method for forced oxidative mechanochemical degradation of active pharmaceutical ingredients (APIs) using clopidogrel hydrogensulfate as a model compound is presented. Considerable and selective formation of degradants occurs already after very short reaction times of less than 15 minutes and the nature of the products is strongly dependent on the used oxidant.

Rhodium-Catalyzed Enantioselective Synthesis of Highly Fluorescent and CPL-Active Dispiroindeno[2,1-c]fluorenes

The enantioselective synthesis of chiral [7]-helical dispirodihydro[2,1-c]indenofluorenes (DSF-IFs) was achieved for the first time in good yields with high er values (er up to 99 : 1). The crucial step of the whole reaction sequence was the enantioselective intramolecular [2+2+2] cycloaddition of tethered triynediols to indenofluorenediols, which was catalyzed by a Rh/SEGPHOS® complex. Further transformations led to the corresponding DSF-IFs. The prepared helically chiral DSF-IFs combine circularly polarized luminescence (CPL) activity (g_lum =∼10^-3 ) with exceptionally high fluorescence quantum yields (up to Φ_lum =0.97).

Investigation of isomerization of dexibuprofen in a ball mill using chiral capillary electrophoresis

Besides the racemate, the S-enantiomer of ibuprofen (Ibu) is used for the treatment of inflammation and pain. Since the configurational stability of S-Ibu in solid state is of interest, it was studied by means of ball milling experiments. For the evaluation of the enantiomeric composition, a chiral CE method was developed and validated according to the ICH guideline Q2(R1). The addition of Mg²⁺ , Ca²⁺ , or Zn²⁺ ions to the background electrolyte (BGE) was found to improve Ibu enantioresolution. Chiral separation of Ibu enantiomers was achieved on a 60.2 cm (50.0 cm effective length) x 75 μm fused-silica capillary using a background electrolyte (BGE) composed of 50 mM sodium acetate, 10 mM magnesium acetate tetrahydrate, and 35 mM heptakis-(2,3,6-tri-O-methyl)-β-cyclodextrin (TM-β-CD) as chiral selector. The quantification of R-Ibu in the mixture was performed using the normalization procedure. Linearity was evaluated in the range of 0.68-5.49% R-Ibu (R² = 0.999), recovery was found to range between 97 and 103%, the RSD of intra- and interday precision below 2.5%, and the limit of quantification for R- in S-Ibu was calculated to be 0.21% (extrapolated) and 0.15% (dilution of racemic ibuprofen), respectively. Isomerization of S-Ibu was observed under basic conditions by applying long milling times and high milling frequencies.

Synthesis of selectively 4-substituted 9,9′-spirobifluorenes and modulation of their photophysical properties

Synthesis of selectively 4-substituted 9,9′-spirobifluorenes was accomplished by using catalytic [2 + 2 + 2]-cyclotrimerization of specifically substituted diynols with alkynes to the corresponding fluorenols.