title: Synthesis, NMR and crystallographic studies of 2-substituted dihydroquinazolinones derived from (S)-phenylethylamine.
abstract: 2,3-Dihydro-3-[(S)-1-phenethyl]quinazolinone and some new 2-substituted derivatives bearing isopropyl, o-nitrophenyl and p-nitrophenyl groups were prepared in 40-90% yield by amidation of isatoic anhydride with (S)-phenylethylamine, followed by condensation with triethyl orthoformate, isopropylaldehyde, o-nitro- and p-nitro-benzaldehyde, respectively. The two 2-subtituted dihydroquinazolinones obtained either by using isopropylaldehyde, o-nitro- or p-nitrobenzaldehyde, were separated and purified before their NMR spectra in CDCl3 solutions were recorded. The detection of the low energy conformation of O=C-N-phenethyl segment in solution allowed the correlation of the NMR data with the configuration of newly stereogenic carbon C-2; thus, one diastereomer was labeled SS while the other was RS. Configurations determined by the NMR method were corroborated by X-ray diffraction analysis. X-ray structures of each diastereomeric series showed characteristic conformational types: a propeller-like for the SS and a hairpin for the RS series. Interatomic distances of the hairpin conformation suggest the existence of intramolecular face-to-face interactions between two aromatic rings.
authors.affiliation: Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos. Av. Universidad No. 1001, Col. Chamilpa, C.P. 62210 Cuernavaca-Mor. México. jaime@ciq.uaem.mx
authors.forename: Jaime
authors.initials: J
authors.lastname: Escalante
authors.forename: Claudia
authors.initials: C
authors.lastname: Ortíz-Nava
authors.forename: Patricia
authors.initials: P
authors.lastname: Flores
authors.forename: Jaime M
authors.initials: JM
authors.lastname: Priego
authors.forename: Cirilo
authors.initials: C
authors.lastname: García-Martínez
mesh_terms: D018360:Crystallography, X-Ray; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010627:Phenethylamines / Q000737:chemistry*; D052999:Quinazolinones / Q000138:chemical synthesis* / Q000737:chemistry*
chemical_list: D010627:Phenethylamines; D052999:Quinazolinones