Solution and solid structure of a boc-protected piperidine-spiro-hydantoin as studied by two-dimensional NMR and X-ray crystallography

Molecular structure of a Boc-protected piperidine-spiro-hydantoin has been studied by solution state NMR and X-ray crystallography. Complete assignments of the 1H and 13C spectra have been performed using homo- and heteronuclear 2D NMR techniques. The 1H NMR indicates that the molecule is asymmetric at low temperature and exhibits a C–N bond rotational process of the carbamate fragment attached to the piperidine ring. Solution conformation of the molecule was derived from NOE constraints, in which the piperidine ring exhibits a single half-chair conformation. The crystal structure of the piperidinespiro- hydantoin determined by X-ray crystallography showed that the piperidine ring adopts the same conformation as in solution state and the exocyclic carbamate group is twisted from the potential symmetrical plane of the piperidine ring. q 2003 Elsevier B.V. All rights reserved.