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Crystal Structures of a New Polymorphic Form of Gabapentin Monohydrate and the E and Z Isomers of 4‐Tertiarybutylgabapentin
Author(s) -
Vasudev Prema G.,
Aravinda Subrayashastry,
Ananda Kuppanna,
Veena Shettykere Dayananda,
Nagarajan Kuppuswamy,
Shamala Narayanaswamy,
Balaram Padmanabhan
Publication year - 2009
Publication title -
chemical biology and drug design
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.59
H-Index - 77
eISSN - 1747-0285
pISSN - 1747-0277
DOI - 10.1111/j.1747-0285.2008.00726.x
Subject(s) - gabapentin , cyclohexane , crystal structure , chemistry , crystallography , crystal (programming language) , molecule , group (periodic table) , space group , stereochemistry , polymorphism (computer science) , x ray crystallography , organic chemistry , physics , gene , medicine , biochemistry , alternative medicine , optics , pathology , computer science , diffraction , genotype , programming language
Gabapentin, a widely used antiepileptic drug, crystallizes in multiple polymorphic forms. A new crystal form of gabapentin monohydrate in the space group P bca is reported and the packing arrangement compared with that of a previously reported polymorph in the space group P 2 1 /c [Ibers, J.A. (2001) Acta Crystallogr; C57:641]. Gabapentin polymorphs can also occur from a selection of one of the two distinct chair forms of the 1,1‐disubstituted cyclohexane. Crystal structures of the E and Z isomers of 4‐ tert ‐butylgabapentin provide models for analyzing anticipated packing modes in the conformational isomers of gabapentin. The E isomer crystallized in the space group P ca2 1 , while the Z isomer crystallized in the space group P 2 1 /c. The crystal structure of E ‐4‐ tert ‐butylgabapentin provides the only example of a structure in a non‐centrosymmetric space group. Crystal structures of the hydrochloride and hydrobromide salts of 4‐ tert ‐butyl derivatives are reported. The results suggest that for gabapentin, a large ‘polymorph‐space’ may be anticipated, in view of the multiple conformational states that are accessible to the molecule.