jo0509096_si_002.cif (26.88 kB)

Organic Crystal Engineering with 1,4-Piperazine-2,5-diones. 6. Studies of the Hydrogen-Bond Association of Cyclo[(2-methylamino-4,7-dimethoxyindan-2-carboxylic acid)(2-amino-4,7-dimethoxyindan-2-carboxylic acid)]

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posted on 28.10.2005, 00:00 by Robin A. Weatherhead-Kloster, Hugh D. Selby, Walter B. Miller, Eugene A. Mash
The title 1,4-piperazine-2,5-dione was synthesized in 23% yield over six steps from ethyl 2-amino-4,7-dimethoxyindan-2-carboxylate. Crystallization by slow diffusion of ether into a chloroform solution and by slow evaporation of an ethanol−chloroform−benzene solution produced polymorphic crystalline forms as determined by single-crystal X-ray analysis. The polymorphs exhibited different hydrogen-bonding networks. The association of this piperazinedione in solution was studied using mass spectrometric and nuclear magnetic resonance spectroscopic techniques. The MS and NMR data were interpreted using the solid-state structures as models for solution aggregation. Association constants extracted from the NMR data are in line with those of other cyclic cis amides in chloroform solvent.