Semipreparative enantiomer separation of propranolol hydrochloride by high-performance liquid chromatography using cellulose tris(3,5-Dimethylphenylcarbamate) chiral stationary phase.

In this paper, we describe the direct semipreparative resolution of racemic (rac)-propranolol hydrochloride by high-performance liquid chromatography using cellulose tris(3,5-dimethylphenylcarbamate) as chiral stationary phase and mobile phase systems containing petroleum ether and 2-propanol with the use of basic additives. At analytical scale, the retention factor of both enantiomers is less than 5 with the separation factor 1.95 and the resolution 2.4. Then, the analytical method is scaled up to semipreparative loading to obtain small amounts of both propranolol hydrochloride enantiomers. Petroleum ether, rather than n-hexane, is used to effectively reduce the production cost of (R)- and (S)-propranolol. To increase the throughput, overlapping injections are used, allowing an injection to be made every 6.5 min instead of every 12 min. At semipreparative scale, approximately 19 mg/h enantiomers are isolated. The first fraction [(R)-(+)-propranolol hydrochloride] is isolated with a purity of > 99.6% (e.e.) and > 97.0% yield, and the second [(S)-(-)-propranolol hydrochloride] is isolated with a purity of > 99.3% (e.e.) and > 95.0% yield. In addition, optical rotations of both propranolol hydrochloride enantiomers isolated are investigated.