No abstract

No abstract

An improved procedure for the synthesis of 2-substituted 2,3-dihydro-4(1H)-quinazolinones through diastereomer separation of the corresponding quinazolinones derivatives is presented. The determination of their absolute configurations was obtained by X-Ray diffraction.

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-nitrobenzaldehyde, 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 CDCl 3 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. Molecules 2007, 12 174

Fused pyrimidine derivatives R 0515Synthesis of 2,3-Dihydro-4(1H)-quinazolinones. -Improved procedures are described for the synthesis of title compounds bearing chiral substituents at N-3. -(ESCALANTE*, J.; FLORES, P.; PRIEGO, J. M.; Heterocycles 63 (2004) 9, 2019-2032; Chem. Res. Cent., Univ. Auton. Estado Morelos, 62210 Cuernavaca, Mex.; Eng.) -Mais 05-134