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Synthesis, NMR and Crystallographic Studies of 2-Substituted Dihydroquinazolinones Derived from (S)-Phenylethylamine
Centro de Investigaciones Químicas, Universidad Autónoma del Estado de Morelos. Av. Universidad No. 1001, Col. Chamilpa, C.P. 62210 Cuernavaca-Mor. México
Universidad Autónoma Metropolitana, Area de Química. San Pablo No. 180, Col. Reynosa Tamaulipas, México 02200, D.F.
* Authors to whom correspondence should be addressed.
Received: 5 December 2006; in revised form: 2 February 2007 / Accepted: 5 February 2007 / Published: 12 February 2007
Abstract: 2,3-Dihydro-3-[(S)-1-phenethyl]quinazolinone and some new 2-substitutedderivatives bearing isopropyl, o-nitrophenyl and p-nitrophenyl groups were prepared in40-90% yield by amidation of isatoic anhydride with (S)-phenylethylamine, followed bycondensation with triethyl orthoformate, isopropylaldehyde, o-nitro- and p-nitro-benzaldehyde, respectively. The two 2-subtituted dihydroquinazolinones obtained eitherby using isopropylaldehyde, o-nitro- or p-nitrobenzaldehyde, were separated and purifiedbefore their NMR spectra in CDCl3 solutions were recorded. The detection of the lowenergy conformation of O=C-N-phenethyl segment in solution allowed the correlation ofthe NMR data with the configuration of newly stereogenic carbon C-2; thus, onediastereomer was labeled SS while the other was RS. Configurations determined by theNMR method were corroborated by X-ray diffraction analysis. X-ray structures of eachdiastereomeric series showed characteristic conformational types: a propeller-like for theSS and a hairpin for the RS series. Interatomic distances of the hairpin conformationsuggest the existence of intramolecular face-to-face interactions between two aromaticrings.
Keywords: Chiral dihydroquinazolinones; π-stacking interactions; NMR method; configurational analysis.
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MDPI and ACS Style
Escalante, J.; Ortíz-Nava, C.; Flores, P.; Priego, J.M.; García-Martínez, C. Synthesis, NMR and Crystallographic Studies of 2-Substituted Dihydroquinazolinones Derived from (S)-Phenylethylamine. Molecules 2007, 12, 173-182.
Escalante J, Ortíz-Nava C, Flores P, Priego JM, García-Martínez C. Synthesis, NMR and Crystallographic Studies of 2-Substituted Dihydroquinazolinones Derived from (S)-Phenylethylamine. Molecules. 2007; 12(2):173-182.
Escalante, Jaime; Ortíz-Nava, Claudia; Flores, Patricia; Priego, Jaime M.; García-Martínez, Cirilo. 2007. "Synthesis, NMR and Crystallographic Studies of 2-Substituted Dihydroquinazolinones Derived from (S)-Phenylethylamine." Molecules 12, no. 2: 173-182.