Primary and. beta. -secondary deuterium isotope effects in N-deethylation reactions
Lidocaine (1), labeled specifically with deuterium in the ..cap alpha..-methylene (lidocaine-d/sub 4/, 2) and ..beta..-methyl (lidocaine-d/sub 6/, 3) carbon atoms of the terminal amino group, was used to probe the mechanism of oxidative N-deethylation by rat liver microsomes. The reaction rates were determined by measuring the formation of acetaldehyde colorimetrically. This general assay for oxidative N-deethylation reactions has the advantages of being rapid, producing a relatively stable colored derivative and being linear over the range of 0.25-4 ..mu..g of acetaldehyde formed per milliliter of incubate. Deuterium substitution at the methylene carbon atoms, the presumed site of initial oxygen insertion, revealed a k/sub H//k/sub D/ = 1.49 +- 0.11 and a K/sub m//sup D//K/sub m//sup H/ = 1.23. Deuterium substitution on the terminal methyl groups showed a k/sub H//k/sub D/ = 1.52 +- 0.10 and a K/sub m//sup D//K/sub m//sup H/ = 0.92. The results are explained in terms of both primary and secondary isotope effects on a possible rate-determining step in the N-deethylation sequence.
- Research Organization:
- Univ. of California, San Francisco
- OSTI ID:
- 7343389
- Journal Information:
- J. Med. Chem.; (United States), Journal Name: J. Med. Chem.; (United States) Vol. 18:1; ISSN JMCMA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400202* -- Isotope Effects
Isotope Exchange
& Isotope Separation
AMINES
CELL CONSTITUENTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DEUTERIUM
HYDROGEN ISOTOPES
ISOTOPE EFFECTS
ISOTOPES
KINETICS
LIGHT NUCLEI
MICROSOMES
NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
REACTION KINETICS
STABLE ISOTOPES