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Cl
Cl
H
Aq. Cl
2
Aq. Cl
2
HO
HO
HO
N
N
N
O
H
O
H
O
Cl
I
II
-HCl
H
pH < 6
H
-
-
HO
C NHCl
C = N - Cl + CO
2
H
2
O
H
H
IV
III
pH ≥ 6
Hydrolysis
-HCl
H
—
Chloramines +
-
-
H — C — N
HO
C OH
H
V
Aq. Cl
2
VI
N
2
+ NO
3
-
Aq. Cl
2
Aq. Cl
2
Hydrolysis
-
VII
Chloramines +
CO
2
Cl - C - N
Aq. Cl
2
pH 9 Buffer
CNO
-
Figure 3.4.
Proposed mechanism of glycine chlorination (compounds drawn in boxes
are the terminal products; intermediates drawn in brackets were not directly detected
by NMR and are only proposed as logical intermediates in the formation of cyanogen
chloride (VII), N
2
, and nitrate) (adapted from Mehrsheikh et al. [40] with the permis-
sion of Elsevier Inc.).
inhibit the activity of endothelial cell nitric oxide synthase and, hence, the
formation of NO
•
[30]. His also reacted rapidly with HOCl to form short-lived
chloramine, which then transferred chlorine to other amine groups to produce
more stable chloramines [33]. The resulting chloramines may further produce
carbonyl products (e.g., 2-oxo-histidine) through either one- or two-electron
processes [30].
Identification of products from the oxidation of Trp by HOCl remains
unclear. The formation of kynurenine and
N
-formylkynurenine (NFK) has
been determined by UV-visible (UV-vis) spectroscopy [42]. The proposed
radical-mediated mechanism yielded these products of the reaction. Initially,
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