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Using crystal structure prediction to rationalize the hydration propensities of substituted adamantane hydrochloride salts

Authors :
Durga Prasad Karothu
Sharmarke Mohamed
Panče Naumov
Source :
Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials. 72:551-561
Publication Year :
2016
Publisher :
International Union of Crystallography (IUCr), 2016.

Abstract

The crystal energy landscapes of the salts of two rigid pharmaceutically active molecules reveal that the experimental structure of amantadine hydrochloride is the most stable structure with the majority of low-energy structures adopting a chain hydrogen-bond motif and packings that do not have solvent accessible voids. By contrast, memantine hydrochloride which differs in the substitution of two methyl groups on the adamantane ring has a crystal energy landscape where all structures within 10 kJ mol−1of the global minimum have solvent-accessible voids ranging from 3 to 14% of the unit-cell volume including the lattice energy minimum that was calculated after removing water from the hydrated memantine hydrochloride salt structure. The success in using crystal structure prediction (CSP) to rationalize the different hydration propensities of these substituted adamantane hydrochloride salts allowed us to extend the model to predict under blind test conditions the experimental crystal structures of the previously uncharacterized 1-(methylamino)adamantane base and its corresponding hydrochloride salt. Although the crystal structure of 1-(methylamino)adamantane was correctly predicted as the second ranked structure on the static lattice energy landscape, the crystallization of aZ′ = 3 structure of 1-(methylamino)adamantane hydrochloride reveals the limits of applying CSP when the contents of the crystallographic asymmetric unit are unknown.

Details

ISSN :
20525206
Volume :
72
Database :
OpenAIRE
Journal :
Acta Crystallographica Section B Structural Science, Crystal Engineering and Materials
Accession number :
edsair.doi...........85ac329c75f253c0c5877891b10fb5fc