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X-ray crystal structures have been determined of five compounds closely related to N-benzyl-2-azaspiro[4.4]-nonane-l,3-dione (1), which is inactive as an anticonvulsant, and N-(benzyloxy)-2-azaspiro[4.4]nonane-1,3-dione (2), which is active. Conformational analyses have been carried out with (1), (2) and the new compounds N-(2',4'-dichlorobenzyloxy)-2-azaspiro[4.4]nonane-l,3-dione (3), N-(2'-bromobenzyloxy)-2-azaspiro[4.4]nonane-l,3-dione (4), N-(4'-(trifluoromethyl)benzyloxy)-2-azaspiro[4.4]nonane-l,3-dione (5), which are all active anticonvulsants, and N-(4'-chlorobenzyloxy)-2-azaspiro[4.4]nonane-l,3-dione (6) and N-(4'-bromobenzyloxy)-2-azaspiro[4.4]nonane-1,3-dione (7), which are inactive. Regardless of the substitution pattern, the conformations of compounds (2)-(7) in the crystals are very similar. Among the low-energy conformations, which are well distributed in the conformational space, that present in its solid state is dominant. Ortho-substitution considerably cuts down the number of conformations accessible within the set energy limit. The results of these studies alone do not explain the differences in activity.

Supporting information

cif

Crystallographic Information File (CIF)
Contains datablocks 3, 4, 5, 6, 7, text

fcf

Structure factor file (CIF format)
Contains datablock 3

fcf

Structure factor file (CIF format)
Contains datablock 4

fcf

Structure factor file (CIF format)
Contains datablock 5

fcf

Structure factor file (CIF format)
Contains datablock 6

fcf

Structure factor file (CIF format)
Contains datablock 7

CCDC references: 131695; 131696; 131697; 131698; 131699

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