| Autor: |
Sparr, Christof, Salamanova, Evdokiya, Schweizer, W. Bernd, Senn, Hans Martin, Gilmour, Ryan |
| Zdroj: |
Chemistry - A European Journal; August 2011, Vol. 17 Issue: 32 p8850-8857, 8p |
| Abstrakt: |
The preference of β‐fluoroimines to adopt a gaucheconformation has been studied by single‐crystal X‐ray diffraction analysis and DFT methods. Empirical and theoretical evidence for a preferential gauchearrangement around the NCCF torsion angle (ϕ) is presented ((E)‐2‐fluoro‐N‐(4‐nitrobenzylidene)ethanamine: ϕNCCF=70.0°). In the context of this study, the analysis of a pyridoxal‐derived β‐fluoroaldimine was performed, a species that is implicated in the inhibition of pyridoxal phosphate (PLP)‐dependent enzymes by β‐fluoroamine derivatives. The gauchepreference of the internal aldimine (=NCH2CH2F) that can be rationalized by stereoelectronic arguments does not hold for the corresponding external system (NCHCH2F) (Eminwhen ϕNCCF=120°). Moreover, the CF bond is lengthened by more than 0.02 Å at ϕNCCF=±90°, when it is exactly antiperiplanar to the conjugated imine. This activation of the CF σ bond by an adjacent π system constitutes an addendum to Dunathan’s stereoelectronic hypothesis. |
| Databáze: |
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