Efficient chiral separation of R- and S-valsartan via diastereomeric crystallization using natural dehydroabietylamine

This work dealt with the chiral separation of the R- and S-valsartan mixture, where R- is an undesired coproduct formed in the production of S-valsartan. 1H NMR and molecular simulation calculation indicated the dehydroabietylamine (DHAA) has well chiral recognition ability to valsartan enantiomers. DHAA successfully employs the resolution of R- and S-valsartan via diastereomeric crystallization. The main parameters affecting the enantio-separation process, such as solvent, the molar ratio DHAA/valsartan, liquid-solid ratio of solvent/valsartan, reaction and crystallization temperature, were investigated and optimized by employing a Box-Behnken design and the response surface methodology (RSM). At the optimal resolution conditions, the chiral separation gave purity of 99.1% and yield of 87.2% for the S-valsartan. These results provide an industrially viable and efficient separation of valsartan enantiomers. Consequently, the established separation method can use to recycle the S-valsartan from the R-/S-valsartan mixture and promote sustainable development for the manufacturing of S-valsartan.