By nature designed enzymes are optimized for highly selective chemical transformations under mild conditions. However, they do not catalyze reactions like olefin oligomerization, allylic substitution or hydroformylation, which are typically catalyzed by transition metal complexes.
Artificial metalloenzymes (ArMs) represent the combination of these metal complexes with selectivity inducing protein scaffolds. This enables the exploitation of the highly sophisticated molecular recognition mechanism of biological macromolecules and the activity of transition metals towards abiological reactions like hydroformylation or oligomerization of ethene. Herein we represent further developments of SCP-2L-based ArMs aiming for C-C-coupling reactions. For this purpose, the active metal center needs to be incorporated by bioconjugation of phosphines, P-ylides or a-diimines to the protein inside of the long lipophilic tunnel of SCP-2L.

Bioconjugation proceeds via the established maleimide-cystein technology and the hydrazide-hydrazone-approach to anchor the phosphine/P-ylide. Maleimide bearing a-diimines are directly incorporated. Subsequently, the protein is reacted with an appropriate metal source to gain access to the desired reactivity.

Prospects
The bioconjugated phosphine can be subjected to a broad range of transition metal sources, thereby inducing the desired reactivity. It is planned to react the bioconjugates with Pd, Rh or Ni sources to gain access to allylic substitution, hydroformylation (or related reactions) or selective oligomerization of ethene, respectively. Especially the selective oligomerization of ethene appears to be a promising reaction to exploit the long lipophilic tunnel of SCP-2L.

<b>Figure 1.</b> Synthetic approach towards P-containing conjugates.

Figure 1. Synthetic approach towards P-containing conjugates.

Jan-Ole Moritz

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