NMR and computational study on the anomeric effect in cis/trans-3,4-dihydro-2-alkoxy-4-substituted-2H,5H-pyrano[3,2-c][1]benzopyran-5-one derivatives

✍ Scribed by Rita Annunziata; Laura Raimondi; Gian Mario Nano; Giovanni Palmisano; Silvia Tagliapietra

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 354 KB
• Volume: 35
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/(sici)1097-458x(199711)35:11<721::aid-omr161>3.0.co;2-i

✦ Synopsis

The conÐguration and conformation of cis/trans-3,4-dihydro-2-alkoxy-4-(alkylor aryl-substituted)-2H,5Hpyrano [ 3,2-c ] [1]benzopyran-5-one derivatives were studied by combined NMR and computational analyses. The cis/trans conÐgurational assignments of all diastereoisomers were achieved via 2D NOESY experiments. The conformational analysis of cis compounds, performed via NMR and computational studies, allowed the establishment of a preference for the conformer with both substituents in the pseudo-equatorial orientations. For trans derivatives only the molecular mechanics analysis produced meaningful results, suggesting a general prevalence for the conformer bearing the 2-alkoxy group in a pseudo-axial and the 4-substituent in a pseudo-equatorial orientation.