Concept explainers
Epoxide Rearrangements and the NIH Shift
This passage is about two seemingly unrelated aspects of
epoxide rearrangements
arene oxides
These two topics merge in an important biological transformation in which neither the
reactant nor the product is an epoxide
Epoxide rearrangements
In some epoxide ring-opening reactions
As positive charge develops on the ring carbon, one of the groups on the adjacent carbon migrates to it. This migration is assisted by electron
all of this occurs in the same transition state. Subsequent deprotonation gives an
Overall, the reaction resembles the pinacol rearrangement of vicinal
Descriptive Passage and Interpretive Problems) and takes place under similar conditions.
Arene Oxides
Aromatic rings are normally inert to the customary reagents that convert
arene oxides have been synthesized in the laboratory, often by indirect methods. Their chemical
reactivity resembles that of other epoxides.
The most striking thing about arene oxides is their involvement in biological processes. Enzymes
In the liver oxidize
The NIH shift
Although hydroxylation of phenylalanine to tyrosine looks like a typical electrophilic aromatic sub stitution, scientists at the U.S. National Institutes of Health discovered that the biochemical pathway combines epoxidation of the benzene ring followed by epoxide ring opening with rearrangement. This rearrangement, which is the biochemical analog of the pinacol
Acetanilide, which has pain-relieving properties, undergoes a biochemical oxidation
similar to that of the NIH shift that occurs with phenylalanine. The product formed from
acetanilide is itself a pain reliever. What is the structure of this substance (better known as
Tylenol)?
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- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage Learning