Circular dichroism and absolute configuration of Aza- and Thiaflavanones

✍ Scribed by Antus, Sándor ;Baitz-Gács, Eszter ;Kajtár, Judit ;Snatzke, Günther ;Tőkés, Adrienne L.

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 629 KB
• Volume: 1994
• Category: Article
• ISSN: 0947-3440
• DOI: 10.1002/jlac.15619940509

✦ Synopsis

Abstract

The correlation between the absolute configuration and CD of aza‐ and thiaflavanone (1, 2) is discussed: the 2__R__ configuration for the laevorotatory enantiomers has been established by a comparison of their CD data with those of (S)‐(−)‐3. For the Cotton effect within the n → π^*^ band of 1 and 2 the same helicity rule is valid as for the homochirally analogous flavanones (3). Starting from (S)‐(−)‐flavanone (3) and cholesterol (5), we have synthesized the chromane derivatives 4 and 20, respectively. The ^1^L~b~ band of the chromane chromophore has been unequivocally identified in the range between 255 and 290 nm in the CD spectra of 4 and 20. For this Cotton effect the opposite helicity rule is valid as compared with the homochirally analogous tetralins: the P/M helicity of the hetero ring leads to a negative/positive CD within the ^1^L~b~ band. The modification of the helicity rule can be explained with the help of Petruska's “q values”. magnified image