Historically, many compelling therapeutic targets have been accessible only by injectable biologic drugs. Macrocyclic peptides, such as the proprotein convertase subtilisin/kexin type 9 inhibitor enlicitide for the treatment of atherosclerotic cardiovascular disease, are beginning to unlock these targets to orally administered therapies to enable broader patient access. We report the convergent biocatalytic assembly of enlicitide from simple building blocks enabled by a suite of engineered enzymes to catalyze selective peptide fragment formation, coupling, and macrocyclization in a protecting group–free manner. Together with efficient crystallizations that obviate the need for chromatography, this approach reduces the number of steps by greater than half compared with prior state-of-the-art methods, addressing long-standing synthetic challenges and offering a sustainable blueprint for the scalable development of complex peptide therapeutics.

Chemical investigations of a marine sponge-associated Bacillus revealed six new imidazolium-containing compounds, bacillimidazoles A–F (1–6). Previous reports of related imidazolium-containing natural products are rare. Initially unveiled by timsTOF (trapped ion mobility spectrometry) MS data, extensive HRMS and 1D and 2D NMR analyses enabled the structural elucidation of 1–6. In addition, a plausible biosynthetic pathway to bacillimidazoles is proposed based on isotopic labeling experiments and invokes the highly reactive glycolytic adduct 2,3-butanedione. Combined, the results of structure elucidation efforts, isotopic labeling studies and bioinformatics suggest that 1–6 result from a fascinating intersection of primary and secondary metabolic pathways in Bacillus sp. WMMC1349. Antimicrobial assays revealed that, of 1–6, only compound six displayed discernible antibacterial activity, despite the close structural similarities shared by all six natural products.

Cyclic peptides have been excellent source of drug leads. With the advances in discovery platforms, the pharmaceutical industry has a growing interest in cyclic peptides and has pushed several into clinical trials. However, structural complexity of cyclic peptides brings extreme challenges for structure elucidation efforts. Isotopic fine structure analysis, Nuclear magnetic resonance (NMR), and detailed tandem mass spectrometry rapidly provided peptide sequence for streptnatamide A, a cyclic peptide isolated from a marine‐derived Streptomyces sp. Marfey's analysis determined the stereochemistry of all amino acids, enabling the unambiguous structure determination of this compound. A non‐ribosomal peptide synthetase biosynthetic gene cluster (stp) was tentatively identified and annotated for streptnatamide A based on the in silico analysis of whole genome sequencing data. These analytical tools will be powerful tools to overcome the challenges for cyclic peptide structure elucidation and accelerate the development of bioactive cyclic peptides.