Chemistry Reference
In-Depth Information
16
N-H protons were deprotonated. The anion of
17
was attached to PCD by mixing it
with the polymer;
17
is thus triply attached to PCD (
18
). After the chloro groups of
18
were displaced with methoxide, the resulting resin was treated with acid and then with
CuCl
2
to produce
19
. The active site in
19
contains three convergent Cu(
II
) complexes
of tris(2-aminoethyl)amine. On incubation with
19
, neutral amide substrate
12
was
unaffected whereas carboxyl-containing amides
13
-
15
were hydrolyzed effectively
(Figure 3.10). The mechanismdepicted in
20
was proposed to account for the substrate
selectivity manifested for the carboxyl-containing amides.
The k
cat
estimated for the amide hydrolysis by
11
or
19
was much greater than either
0.1 h
-1
at pH 8.5 and 50
8
C or 0.2 h
-1
at pH 8 and 50
8
C. This k
cat
may be compared with
the 0.18 h
-1
for hydrolysis of an amide substrate (at the optimum pH of 9 and 25
8
C)
observed with a catalytic antibody [54] that had been elicited by a joint hybridoma and
combinatorial antibody library approach.
Figure 3.10 pH dependence of k
o
for the hydrolysis of 13-15
(S
o
= 1.96
10
-4
M
:
&
, 13;
*
, 14;
^
, 15) catalyzed by 19 (C
o
= 5.80
10
-4
M
)at50
8
C. Unlike the carboxyl-containing amides, the neutral
amide (12) was not hydrolyzed.
