1 Pharmaceutical Analytical & Solid-State Chemistry Research Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China. xuefengmei@simm.ac.cn.
A four-membered square-shaped H-bonding structure was successfully designed to synthesize vitamin D3 co-crystals. The co-crystallization process was found to be conformationally selective to result in topochemically stable materials.