CHM 4139 Lecture Notes - Lecture 16: Polar Effect, Electrophilic Aromatic Substitution, Allyl Group
12 Nov 2016
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Chm 4139- lecture 16: determination of enzyme mechanisms. Rep. 2015,32,88-101: use of isotopically-labelled substrates [fig 4] Using isotopically-labelled substrates (dmapp), it was established that the dimethyl allyl group of dmapp is transferred onto the indole ring of the trp with inversion of configuration at the c-2 methylene position. No isotopic scrambling of the methyl groups occurred during the process. Isotopic scrambling: the process of achieving an equilibrium distribution of isotopes with a specified set of atoms of a chemical species. (highlighted in yellow) Atom can break off during a reversible reaction, and when it reforms the same bond, the position shifted due to bond rotation. This indicates that double-bond in dimethyl allyl group is not broken and that methylene is attacked by trp (could be sn1 or sn2, no way to determine yet. : use of substrate analogues containing electron-withdrawing group. Use fluorine as it is the more electronegative and it is very small.
