Molecular and Crystal Characterisation of 13-cis-5,6-Dihydro-5,6-epoxy Retinoic AcidA potential impurity of isotretinoin Luciana Malpezzi a, Silvia Armellin a, Elisabetta Brenna a, Claudio Fuganti a, Mario Fantucci b, Grato Angelo Magnone b, and Cesare Pellegatta b Dipartimento di Chimica del Politecnico, Milan (Italy) a, and Laboratori MAG, Milan (Italy) b 13-cis-5,6-Dihydro-5,6-epoxy retinoic acid, a degradation product formed when 13-cis-retinoic acid is exposed to light and/or atmospheric oxygen, has been synthesised and its molecular conformation and crystal structure have been investigated by X-ray single crystal diffraction. The geometry of the molecule is compared with that of previously acquired pure 13-cis-retinoic acid. The epoxy group is disordered over two adjacent cyclohexane bonds with different site-occupation factors. In the crystal, the molecules form centrosymmetric dimers through hydrogen bonds between carboxylic acid groups. The X-ray powder diffraction pattern, together with a list of the most prominent peaks, and the thermal analysis of the compound are also reported to better characterize the product. Key words Isotretinoin · Retinoic acid, degradation product, epoxy derivative, X-ray structure |
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pharmind 2002, Nr. 6, Seite 607
