Chemistry Reference
In-Depth Information
1
Artificial Enzymes
Ronald Breslow
Biomimetic Chemistry, including that involved in the synthesis and study of artificial
enzymes, has grown to enormous proportions. Even the part of the field using cyclo-
dextrins as binding groups in synthetic catalysts that mimic enzymes has been the
subject of a large review article [1]. Thus in this chapter I will focus mainly, but
not exclusively, on work from our own laboratory. Other chapters will help make
up for this somewhat narrow focus. I have published several reviews of our work else-
where [2-51].
1.1
Mimics of Enzymes that use Thiamine Pyrophosphate as a Coenzyme
I have been pursuing enzyme mimics, artificial enzymes that perform biomimetic
chemistry, since starting my independent career in 1956. In the first work [52-59]
my co-workers and I studied models for the function of thiamine pyrophosphate
1
as a coenzyme in enzymes such as carboxylase. We discovered the mechanism by
which it acts, by forming an anion
2
that we also described as a stabilized carbene,
one of its resonance forms. We examined the related anions from imidazolium cations
and oxazolium cations, which produce anions
3
and
4
that can also be described as
nucleophilic carbenes. We were able to explain the structure-activity relationships in
this series, and the reasons why the thiazolium ring is best suited to act as a biological
