Preparation of enantiomerically pure compounds remains a challenging task, despite the great progress in asymmetric syntheses and separation techniques. Each enantiomer exhibits identical chemical and physical behaviour in achiral surroundings as its counterpart, but their biochemical and pharmacological properties in the chiral environment of living organisms can differ significantly. Thus, the pressing need for innovative and highly efficient separation technologies allowing for large scale production of enantiomerically pure pharmaceuticals. Technologies based on membrane separations have the potential to play a key role to fulfil these needs.
We present a new chiral home-made membranes based on the modified cyclodextrin in Nafion117® [1], a series of unique composite membranes formed from a nano & micro fibrous material with different amounts of achiral selector [2], and optically active linear polyimides and hyperbranched poly(amic acid – imide) [3], which were used for separation of chiral drugs from water.
We were testing these membranes during preferential sorption and pertraction experiments in a diffusion cell. We report that L – Tryptophan is preferentially bound to the membrane, while D-Tryptophan is transported through the membrane with enantiomeric excess exceeding 80 %, depending on the analyte concentration. To increase the permeation rate and amount of chiral selector attached to the membrane, thinner membrane substrate with higher degree of swelling is proposed. All membranes are compared and new perspectives in this challenging research are shown.
