Chemistry Reference
In-Depth Information
We have also synthesized a catalyst related to
131
in which the cyclodextrin rings
were replaced with synthetic macrocyclic binding groups [196]. Also, we have exam-
ined catalysts related to
131
in which substrate binding involved metal ion coordina-
tion, not hydrophobic binding into cyclodextrins or macrocycles [198].
1.5
Future Prospects
As Philip Ball has pointed out, in biomimesis we take principles from Nature, not
blueprints [199]. That is, we adopt the style of natural chemistry, but do not simply
reproduce the same enzymes by which Nature achieves selectivity. His analogy is very
apt: “A jumbo jet is not just a scaled-up pigeon.“ We learned the principle of wings
from the birds, but not the details of how to use them and power the flight. Thus, in our
work we have adopted the principles of reversible bonding and geometrically directed
selectivity characteristic of natural enzymes, but used very different structures in our
artificial enzymes. Our goal is to “liberate chemistry from the tyranny of functional
groups“ [194].
This new style of synthetic catalysis will of course not replace all normal synthetic
methods. For many purposes, the standard methods and rules - e.g. aldehydes are
more easily reduced than are ketones - will continue to dominate organic synthesis.
However, when we require a synthetic transformation that is not accessible to normal
procedures, as in the functionalization of unactivated carbons remote from functional
groups, artificial enzymes can play a role. They must compete with natural enzymes,
and with designed enzyme mutants, but for practical large-scale industrial synthesis
there can be advantages with catalysts that are more rugged than proteins.
Our work in the development of artificial enzymes, described here and in Chapter 2,
has established that catalysts can be made that will achieve excellent defined geome-
trically directed functionalizations and, furthermore, that the combination of binding
groups with coenzyme analogs leads to powerful catalysts for some reactions. We ex-
pect the field of biomimetic chemistry to continue to grow, as we combine lessons
from Nature with the ingenuity of chemists.
We will learn to produce mimics of enzyme clusters, imitating natural clusters such
as gene transcription assemblies. We will learn to produce artificial enzymes that show
induced fit, and allosteric control by analogs of hormones. Then we will move to mi-
mics of cells themselves, with their components of many enzymes, to achieve chemical
processes more complex than those done by a single enzyme. The biochemistry of life
is impressive, but the role of chemistry is not just to admire it. As humans were im-
pelled to invent ways to fly after observing birds, we will learn to create a new area of
chemistry - biomimetic reaction chemistry - adding both to our understanding and to
our practical abilities.
