Enantiomer self-disproportionation of chiral compounds on achiral ordered mesoporous silica M41S and regular silica gel as a stationary phase.

Chromatographic behavior of nonracemic mixtures, viz., mandelic acid and stilbene oxide as analytes has been studied in detailed by enantiomer self-disproportionation on achiral ordered mesoporous material M41S and regular silica gel as stationary phases. Enantiomer self-disproportionation gave enhanced separation of analytes. The extent and magnitude of enantiomer self-disproportionation is dependent on the optical purity of the starting non-racemic molecules, presence of intermolecular hydrogen bonding/pi-pi interactions and the nature of eluents used. The present study and previous literature data suggest that percentage ee of a nonracemic mixture needs to be determined before any chromatographic purification is taken up as enantiomer self-disproportionation phenomenon could occur during purification. The data show that enantiomer self-disproportionation of nonracemic mixtures can be harnessed for its enantioenrichment on inexpensive achiral stationary phases.

Synthesis and characterization of mesoporous silica modified with chiral auxiliaries for their potential application as chiral stationary phase.

Novel chiral stationary phase (CSP) based on chiral aminoalcohol immobilized on ordered mesoporous silica SBA-15 1a and standard silica 1b and their copper complexes 1a' and 1b', respectively, was synthesized as potential material for chiral ligand exchange chromatography (CLEC). Microanalysis, inductively coupled plasma spectroscopy (ICP), thermo-gravimetric analysis (TGA), cross polarized magic angle spinning (CP-MAS) (13)C NMR, Powder X-ray diffraction (PXRD), FTIR, N(2) adsorption isotherm, scanning electron microscopy (SEM), transmitted electron microscope (TEM) and solid reflectance UV-vis spectroscopy were used to characterize these materials. All the chiral stationary phases thus synthesized were used for the separation of different racemic compounds such as mandelic acid, 2,2'-dihydroxy-1,1'-binaphthalene BINOL) and diethyl tartrate by simple medium-pressure column chromatography. Successful enantio-separation of racemic mandelic acid was achieved with all the stationary phases but 1a and 1b gave slightly better resolution than their copper complexes 1a' and 1b'. Remarkably these materials are stable under the given experimental conditions and can be used repeatedly for several cycles of enantioresolution. It was observed that the porosity and surface area of the stationary phase play an important role in the chiral separation.

Synthesis and characterization of (S)-amino alcohol modified M41S as effective material for the enantioseparation of racemic compounds.

A new chiral stationary phase (CSP) was synthesized based on (S)-1-anilino-3-propyl-2-propanol covalently bonded to the mesoporous semi-crystalline material M41S. Direct semipreparative enantioseparation of mandelic acid could be achieved using medium pressure chromatography. Partly separated could also be the enantiomers of 2,2'-dihydroxy-1,1'-binaphthalene, cyanochromene oxide, diethyl tartrate and 2-phenyl propionic acid. The characterization of CSP was accomplished by microanalysis, cross polarized magic angle spinning (CP-MAS) 13C NMR, powder X-ray diffraction (XRD), FTIR, thermo-gravimetric analysis (TGA), N2 adsorption-desorption isotherm, scanning electron microscopy (SEM) and solid reflectance UV-vis spectroscopy. Furthermore the stability of CSP was satisfactory as it could withstand three washing and reuse experiments of enantioseparation of mandelic acid without loss in its performance.

Montmorillonite-Alginate Composites as a Drug delivery System: Intercalation and In vitro Release of Diclofenac sodium.

Diclofenac sodium and alginate was intercalated into montmorillonite to form uniform sized beads by gelation method. The structure and surface morphology of the synthesized composite beads were characterized by powdered X-ray diffraction, Fourier transform infrared spectroscopy, thermo gravimetric analysis and scanning electron microscopy. Diclofenac release kinetics of the composite in simulated intestinal fluid medium (pH 7.4) and effect of montmorillonite content on the in vitro release of diclofenac from diclofenac-montmorillonite-alginate composites bead was investigated by UV/Vis spectrophotometer. Diclofenac encapsulation efficiency in the montmorillonite-alginate composites bead increases with an increase in the montmorillonite content. The control release of diclofenac from diclofenac-montmorillonite-alginate composites beads was observed to be better as compared to diclofenac-alginate beads.