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References 453

19.5
Conclusion and Outlook
Being a challenging and promising field from both academic and industrial per-
spectives, combination of biocatalysis with chemocatalysis or ‘‘classic chemical’’
processes toward one-pot processes has fast emerged in recent years. A typical
advantage of such processes is the avoidance of time- and capacity-consuming
and waste-producing work-up steps which are required when conducting reactions
in a sequential manner with intermediate isolations and purifications. Further-
more, solvent usage can be dramatically reduced and also space-time yields can
be significantly improved. As a key issue for the setting up of such one-pot
processes – independently of the concept that is applied – one can regard the
achievement of compatibility of the individual steps with each other. So far, two
types of concepts of chemoenzymatic one-pot processes in terms of reaction types
involved have been mainly studied. The first one is based on the isomerization of
a substrate, which is catalyzed by means of a chemocatalyst, and its combination
with an in situ enzymatic transformation of one of the isomers. As isomers, mostly
racemic mixtures of enantiomers are used, which then leads to DKR processes.
The second concept is based on a combination of a substrate synthesis (not
formed by an isomerization process) in an initial step, followed by a subsequent
transformation of the substrate. In these processes, the biotransformation can be
integrated as the initial or as a subsequent step depending on the desired product
and reaction sequence. For these concepts, a range of synthetic examples have now
been developed.
In the future, further one-pot processes based on an extended spectrum of
chemocatalytic and biocatalytic transformations running particularly in aqueous
reaction media (to be able to make use of the full range of enzyme diversity)
can be expected. In addition, the development of a number of one-pot processes
consisting of three or more individual synthetic steps would be desirable. Based on
the developed synthetic ‘‘proof-of-concept’’ processes, it would be also of interest to
conduct process development studies and reaction engineering to further optimize
the one-pot processes in terms of overall conversion, space-time yield, and catalyst
consumption. With respect to the latter, the application of heterogeneous chemo-
and biocatalysts, offering additionally the option of catalyst compartmentalization,
represents an interesting option. Thus, it can be expected that in the future
we will see an increased number of chemoenzymatic one-pot processes with
an extended application range as well as applications at an elevated, technical
scale.

References
1. Comprehensive review about biocatalysis vol. 1–3, Wiley-VCH Verlag GmbH,
in organic synthesis: Drauz, K., Gr¨ oger, Weinheim.
H., and May, O. (eds) (2012) Enzyme 2. Liese, A., Seelbach, K., and Wandrey, C.
Catalysis in Organic Synthesis, 3rd edn, (eds) (2006) Industrial Biotransformations,