Circular Dichroism of 9,10-Dihydrophenanthrene Derivatives Reveals both the Absolute Configuration and Conformation: A Novel Approach to Mislow's Helicity Rule
✍ Scribed by Jacek Gawroński; Piotr Grycz; Marcin Kwit; Urszula Rychlewska
- Publisher
- John Wiley and Sons
- Year
- 2002
- Tongue
- English
- Weight
- 126 KB
- Volume
- 8
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
The absolute configuration and the conformation of 9,10-trans-disubstituted 9,10-dihydrophenanthrenes, known chiral metabolites of phenanthrene-9,10-oxide, have been determined by circular dichroism. The absolute configuration assignment is based on the sign of the long-wavelength Cotton effect (A-band), which is conformation invariant and originates from benzylic chirality. This provides a new interpretation of the Mislow biphenyl-helicity rule for the case of the 9,10-dihydrophenanthrene chromophore. The sign of the B-band Cotton effect reflects the conformation of the biphenyl chromophore in 9,10-dihydrophenanthrenes. It is shown that the origin of chiroptical properties of 9,10-dihydrophenanthrenes is closely related to those of 5,6-trans-disubstituted 1,3-cyclohexadienes.