How To Control Recognition: From Brucinium Double Salts to Racemic Resolution

Abstract

Studying the mechanisms of racemic resolution of the model compound N-(3-nitrobenzoyl)aspartic acid by formation and fractional crystallization of brucinium diastereomeric salts, we found that depending on the environment (solvents) the recognition leads to effective or ineffective racemic resolution. During successful racemic resolution, bis(brucinium)-N-(3-nitrobenzoyl)-l-aspartate hydrate methanol solvate precipitates as the first fraction. In turn, double salts and solid solution are formed in the fruitless racemic resolution. Formation of the double salt results from recognition of centrosymmetric anionic dimers on the common brucinium corrugated layer. The common brucinium corrugated layer together with its solvation sphere participates in recognition of the anions, leading to formation of the solid solution. Changing the solvent system according to its dielectric constant, more dispersive or more directional interactions gain importance. The racemic resolution and formation of bis(brucinium)-N-(3-n...