Chemistry Reference
In-Depth Information
1.4.6
Hydroxylations by Artificial P-450 Enzymes
Metalloporphyrins can catalyze the hydroxylations of solvent species such as cyclohex-
ane. From our studies with cyclodextrin dimers, we concluded that by attaching cy-
clodextrin rings to metalloporphyrins we should be able to bind substrates in water and
achieve selective hydroxylations directed by the geometries of the complexes. This was
successful.
Initially, instead of cyclodextrin complexing, we used metal coordination [189]. With
Fe(
III
) porphyrin
122
carrying 8-hydroxyquinoline groups we epoxidized substrate
123
using Cu
2+
as a bridge (cf.
124
). A metallosalen catalyst was not as effective. We then
synthesized a series of Mn(
III
) porphyrins,
125
-
127
, as well as a Mn(
III
) metallosalen
128
, all carrying attached
-cyclodextrin groups [190]. We examined their ability to
epoxidize the double bonds of substrates that could bind into two of the cyclodextrin
b
