100% conversion and the almost exclusive formation of methylphenylsulfoxide
whereas the Mn-salen complexes alone led to an about 60% conversion with the
almost exclusive formation of methylphenylsulfone (Fig. 4) [33]. Another ArM
was obtained by incorporation of a cobalt(II) Schiff base complex {CoL,
H 2 L = 2,2′-[(1,2-ethanediyl)bis(nitrilopropylidyne)]bisphenol} in BSA and its
catalytic activity in the enantioselective oxidation of a variety of sulfides by H 2 O 2
was studied as a function of pH, temperature, and concentration of catalyst and
oxidant. Under optimal conditions, the BSA–CoL hybrid biocatalyst appeared as
efficient for the enantioselective oxidation of a series of sulfides into the corresponding sulfoxides and reached excellent conversions (up to 100%), chemoselectivity (up to 100%), and good enantiomeric excesses (up to 87% ee) [34].
More recently, the oxygen-binding hemoprotein, myoglobin (Mb), has also been
used by several teams to build up artificial metalloenzymes. The general strategy
used is based on the replacement of its iron-heme prosthetic group by other heme or
non-heme metal complexes. Indeed, this heme is linked inside the hydrophobic
10 Å diameter cavity of the protein by non-covalent interactions, including
hydrophobic interactions, electrostatic interactions via its two carboxylate moieties,
and coordination of its iron by the imidazole of H93 [35]. The prosthetic group of
Mb can be easily removed without impairing its folding to yield apo-Mb, which
shows a free cavity able to accommodate another metal cofactor (Fig. 5) [36].
Fig. 5 Preparation of apo-myoglobin [36] and metal complexes of salen and salophen ligands
[37–41] inserted non-covalently in apo-Mb to get artificial metalloenzymes that catalyze the
stereoselective and chemoselective oxidation of thioanisole as well as iron complexes of heme
derivatives bearing eight anionic carboxylate moieties and of porphycens that catalyze the
hydroxylation of ethylbenzene into 1-phenylethanol by H 2 O 2 [36, 42]
Current Applications of Artificial Metalloenzymes …
371
whereas the Mn-salen complexes alone led to an about 60% conversion with the
almost exclusive formation of methylphenylsulfone (Fig. 4) [33]. Another ArM
was obtained by incorporation of a cobalt(II) Schiff base complex {CoL,
H 2 L = 2,2′-[(1,2-ethanediyl)bis(nitrilopropylidyne)]bisphenol} in BSA and its
catalytic activity in the enantioselective oxidation of a variety of sulfides by H 2 O 2
was studied as a function of pH, temperature, and concentration of catalyst and
oxidant. Under optimal conditions, the BSA–CoL hybrid biocatalyst appeared as
efficient for the enantioselective oxidation of a series of sulfides into the corresponding sulfoxides and reached excellent conversions (up to 100%), chemoselectivity (up to 100%), and good enantiomeric excesses (up to 87% ee) [34].
More recently, the oxygen-binding hemoprotein, myoglobin (Mb), has also been
used by several teams to build up artificial metalloenzymes. The general strategy
used is based on the replacement of its iron-heme prosthetic group by other heme or
non-heme metal complexes. Indeed, this heme is linked inside the hydrophobic
10 Å diameter cavity of the protein by non-covalent interactions, including
hydrophobic interactions, electrostatic interactions via its two carboxylate moieties,
and coordination of its iron by the imidazole of H93 [35]. The prosthetic group of
Mb can be easily removed without impairing its folding to yield apo-Mb, which
shows a free cavity able to accommodate another metal cofactor (Fig. 5) [36].
Fig. 5 Preparation of apo-myoglobin [36] and metal complexes of salen and salophen ligands
[37–41] inserted non-covalently in apo-Mb to get artificial metalloenzymes that catalyze the
stereoselective and chemoselective oxidation of thioanisole as well as iron complexes of heme
derivatives bearing eight anionic carboxylate moieties and of porphycens that catalyze the
hydroxylation of ethylbenzene into 1-phenylethanol by H 2 O 2 [36, 42]
Current Applications of Artificial Metalloenzymes …
371