Computational studies on chiral discrimination mechanism of cellulose trisphenylcarbamate

The calculation of interaction energies between cellulose trisphenylcarbamate (CTPC) and enantiomers of (+/-)-trans-stilbene oxide (1) and (+/-)-trans-1,2-diphenylcyclopropane (2) was performed using QUANTA/CHARMm and MOLECULAR INTERACTION programs to gain an insight into the chiral recognition mechanism of phenylcarbamate derivatives of cellulose. The structure of CTPC was optimized with the CHARMm force field based on the proposed structure of CTPC by X-ray analysis. In chromatographic enantioseparation on CTPC, 1 was completely resolved (alpha = 1.46) and the (R,R)-(+)-isomer eluted first followed by the (S,S)-(-)-isomer, but 2 was not resolved (alpha approximately 1). The results of calculation of interaction energies between CTPC and the enantiomers 1 suggested that the most important adsorbing site of CTPC for 1 may be the NH protons of the carbamate moieties at the 3-position of glucose units, and the (S,S)-(-)-isomer of 1 may interact more closely than the (R,R)-(+)-isomer with CTPC. In contrast, there was little difference in the minimum interaction energies between the enantiomers 2. These calculations agreed with the observed results for the chromatographic resolution on CTPC.