Chemistry Reference
In-Depth Information
Figure 2.7 Stereoelectronic explanation of the preferential reaction of
many pyridoxal ansa compounds on their seemingly more hindered
faces. (Reprinted from Ref. 47. Copyright 1994 American Chemical
Society.)
Figure 2.8 Catalysis by the protonated amine could explain the
stereochemistry of threonine and alo-threonine synthesis by our
catalyst 46 at low pH. (Reprinted from Ref. 47. Copyright 1994
American Chemical Society.)
2.7
Conclusion
Vitamin B6 enzyme models that can catalyze five types of reactions - transamination,
racemization, decarboxylation,
-elimination and replacement, and aldolase-type reac-
tions - have been reviewed. There are also five approaches to construct the vitamin B6
enzyme models: (i) vitamin B6 augmented with basic or chiral auxiliary functional
groups; (ii) vitamin B6 having an artificial binding site; (iii) vitamin B6-surfactant
systems; (iv) vitamin B6-polypeptide systems; (v) polymeric and dendrimeric vitamin
B6 systems. These model systems show rate enhancement and some selectivity in
vitamin B6-dependent reactions, but they are still primitive compared with the real
enzymes. We expect to see improved reaction rates and selectivities in future genera-
tions of vitamin B6 enzyme models. An additional goal, which has not received ade-
b
