Chemical and Pharmaceutical Bulletin
Online ISSN : 1347-5223
Print ISSN : 0009-2363
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Fentanyl and Its Analogue N-(1-Phenylpyrazol-3-yl)-N-[1-(2-phenylethyl)-4-piperidyl]propanamide: 1H- and 13C-NMR Spectroscopy, X-Ray Crystallography, and Theoretical Calculations
María Luisa JimenoIbon AlkortaCarolina CanoNadine JagerovicPilar GoyaJosé ElgueroConcepción Foces-Foces
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2003 Volume 51 Issue 8 Pages 929-934

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Abstract

The oxalate salts and free bases of fentanyl and N-[1-(2-phenylethyl)-4-piperidyl]-N-(1-phenyl-4-pyrazolyl)propanamide, a new lead compound for long-acting analgesia, have been characterized by 1H- and 13C-NMR spectroscopy. The crystal structure of the hydrochloride of N-[1-(2-phenylethyl)-4-piperidyl]-N-(1-phenyl-4-pyrazolyl)propanamide monohydrate has been determined. Two centrosymmetrically related cations, joined through C(phenyl)-H…π contacts, encapsulate a large void that contains pairs of anions and bridged water molecules into a zero-dimensional (0D) supramolecular motif. The cations are linked to this framework via N+H…Cl contacts. GIAO/B3LYP calculations have been carried out to compare the experimental 13C chemical shifts with the absolute shieldings thus calculated. The protonation of both molecules takes place on the piperidine ring (axial protonation), as has been verified both in the solid state (X-ray) and in solution (NMR).

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© 2003 The Pharmaceutical Society of Japan
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