Localized Solvent Effects on the Crystal Habit of tert-Butoxycarbonyl-L-asparagine (BocASN)

Abstract

Solvent selection is one of the most important factors for the control of crystal habits. However, this relationship is poorly understood. The aim of this study was to determine the solvent selectivity to obtain a desired crystal habit using tert-butoxycarbonyl-L-asparagine (BocASN) as a model compound. The [110], [100], and [001] faces were dominant for the BocASN crystals obtained from acetone and ethanol. However, the [011], [100], and [001] faces were dominant for those obtained from methanol. The interactions between the solvent molecules and the functional groups exposed on the crystal surface were examined. The solvent-surface interactions on each surface of the BocASN crystal were dependent on the type of solvent. The different solvent-surface interactions along the a-, b-, and c-axes affected the growth rate and aspect ratio of the crystal. The analysis of the solvent-surface interactions is useful to predict the crystal habit.