Biocatalysis has covered an increasingly important role in the synthesis and manufacturing of pharmaceuticals and other high value compounds. In the interest of expanding the range of synthetically useful reactions accessible via biocatalysts, our group has explored the potential and application of engineered myoglobins for ʻabiologicalʼ carbene transfer catalysis. These transformations provide a direct route for the construction of new carbon-carbon and carbon-heteroatom bonds, including the synthesis of cyclopropane rings, which are key motifs and pharmacophores in many drugs and bioactive natural products. In this award article, we survey the progress made by our group toward the development of myoglobin-based catalysts for asymmetric intermolecular cyclopropanation reactions. The high stereoselectivity exhibited by these biocatalysts in these reactions, combined with their broad substrate scope, scalability, and robustness to high substrate loading and organic cosolvents, contribute to make these systems particularly useful for chemical synthesis and biocatalysis at the preparative scale. Extension of the scope of biocatalytic carbene transfer reactions to include different classes of carbene donor reagents has created new opportunities for the asymmetric synthesis of functionalized cyclopropanes. Furthermore, the integration of myoglobin-catalyzed stereoselective cyclopropanations with chemical diversification of the enzymatic products has furnished attractive chemoenzymatic strategies to access a diverse range of optically active cyclopropane scaffolds of high value for drug discovery, medicinal chemistry, and the synthesis of natural products.

Elaborate chemical synthesis methods allow the production of various types of inorganic nanocrystals (NCs) with uniform shape and size distributions. The transformation of already-synthesized NCs via elemental substitutions can overcome the difficulties facing conventional one-step syntheses. As for ion exchange reactions, the cation exchange reactions proceed much faster than the anion exchange reactions because anions generally have much larger ionic radii than cations within the frameworks of NCs. For ionic NCs above a critical size, the anion framework generally remains intact, and the original shape of the parent NCs is retained throughout the cation exchange reaction. As a special case, we show that thermodynamic instability of exposed planes drives reconstruction of anion frameworks under mild reaction conditions. In contrast, the anion exchange reaction often provides the new NCs with unique structures, such as hollow or anisotropically phase-segregated assemblies. Then, we experimentally show the first example of an unprecedented pseudo-binary Z3-FePd₃ alloy NCs by adding a small amount of In, which is immiscible with Fe but miscible with Pd. Finally, a general outline of the transformation of NCs via element substitution reactions and future prospects in this field are provided.