Abstract

The mystery of the origin of homochirality in Nature has been thoroughly investigated due to the essential role it plays in Chemistry, Biochemistry and Biology. For example, enantiopure compounds are often essential in the pharmaceutical and agrochemical industries. New aspects of chemistry and chirality can be explored by effectively utilizing the unique nature of conglomerate crystals. In some cases, conglomerate crystals can be easily resolved by carefully observing the features of the crystals. Resolution is possible through observation of hemihedrism, macromorphology, circular polarization or various surface features.
Cytosine and 1,2-bis(N-benzoyl-N-methylamino)benzene are two examples of compounds that form centrosymmetric monohydrate racemic crystals but non-centrosymmetric anhydrous conglomerate crystals. Herein, a novel approach to asymmetric amplification by coupling conglomerate crystal formation via dehydration, with subsequent Viedma ripening (i.e. attrition-enchanced deracemization) is being explored. A systematic search of the Cambridge Crystallographic Database for other crystal systems which can undergo desolvation and subsequent chiral amplification is ongoing.
Enantiomer-specific oriented attachment, an essential process in Viedma ripening, was also investigated in guanidine carbonate crystals. Simply boiling or shaking powdered racemic guanidine carbonate in saturated solution leads to the formation of large crystalline clusters. These clusters, characterized by solid-state circular dichroism and X-ray powdered diffraction, were found to be nearly homochiral. Enantiomer-specific oriented attachment can be thought of as a mesoscale analogue of conglomerate crystallization.