Biomolecular machines perform types of complex molecular-level tasks that artificial molecular machines can aspire to. The ribosome, for example, translates information from the polymer track it traverses (messenger RNA) to the new polymer it constructs (a polypeptide) . The sequence and number of codons read determines the sequence and number of building blocks incorporated into the biomachine-synthesized polymer. However, neither control of sequence nor the transfer of length information from one polymer to another (which to date has only been accomplished in man-made systems through template synthesis) is easily achieved in the synthesis of artificial macromolecules. Rotaxane-based molecular machines have been developed that successively add amino acids (including β-amino acids ) to a growing peptide chain by the action of a macrocycle moving along a mono-dispersed oligomeric track derivatized with amino-acid phenol esters. The threaded macrocycle picks up groups that block its path and links them through successive native chemical ligation reactions to form a peptide sequence corresponding to the order of the building blocks on the track. Here, we show that as an alternative to translating sequence information, a rotaxane molecular machine can transfer the narrow polydispersity of a leucine-ester-derivatized polystyrene chain synthesized by atom transfer radical polymerization to a molecular-machine-made homo-leucine oligomer. The resulting narrow-molecular-weight oligomer folds to an α-helical secondary structure that acts as an asymmetric catalyst for the Juliá-Colonna epoxidation of chalcones.

We report on the synthesis and operation of a three-barrier, rotaxane-based, artificial molecular machine capable of sequence-specific β-homo (β) peptide synthesis. The machine utilizes nonproteinogenic β-amino acids, a class of amino acids not generally accepted by the ribosome, particularly consecutively. Successful operation of the machine via native chemical ligation (NCL) demonstrates that even challenging 15- and 19-membered ligation transition states are suitable for information translation using this artificial molecular machine. The peptide-bond-forming catalyst region can be removed from the transcribed peptide by peptidases, artificial and biomachines working in concert to generate a product that cannot be made by either machine alone.

We report on the preparation of a decapeptide through the parallel operation of two rotaxane-based molecular machines. The synthesis proceeds in four stages: (1) simultaneous operation of two molecular peptide synthesizers in the same reaction vessel; (2) selective residue activation of short-oligomer intermediates; (3) ligation; (4) product release. Key features of the machine design include the following: (a) selective transformation of a thioproline building block to a cysteine (once it has been incorporated into a hexapeptide intermediate by one molecular machine); (b) a macrocycle-peptide hydrazine linkage (as part of the second machine) to differentiate the intermediates and enable their directional ligation; and (c) incorporation of a Glu residue in the assembly module of one machine to enable release of the final product while simultaneously removing part of the assembly machinery from the product. The two molecular machines participate in the synthesis of a product that is beyond the capability of individual small-molecule machines, in a manner reminiscent of the ligation and post-translational modification of proteins in biology.

A multidisciplinary approach covering synthetic, physical, and analytical chemistry, high-throughput experimentation and experimental design, process engineering, and solid-state chemistry is used to develop a large-scale (kilomole) Suzuki–Miyaura process. Working against clear criteria and targets, a full process investigation and optimization package is described highlighting how and why key decisions are made in the development of large-scale pharmaceutical processes.

The Ni-catalyzed C(sp3)–C(sp3) cross-coupling of redox-active esters and organozinc reagents is used for the active template synthesis of ‘impossible’ rotaxanes.