Oxazolines and thiazolines, and their oxidized analogs, oxazoles and thiazoles, are present in a myriad of bioactive natural products including thiopeptide antibiotics, metal chelating siderophores, and cyclic peptides (Scheme 1A). Thiopeptides display high antibacterial activity and synthetic efforts that aim to explore their viability as therapeutics remain an active area of research. Siderophores assist in bacterial iron uptake and play a key role in infection. These molecules have translational potential in drug delivery as siderophore-antibiotic conjugates, and as antibiotics targeting metal-dependent enzymes. In addition to natural occurrence, chiral oxazolines are attractive synthesis targets because of their use in asymmetric catalysis as ligands for transition metals catalyzing cyclopropanations of alkenes, asymmetric aldol, and cross coupling reactions. In addition to synthesis targets, azolines can also be valuable synthons as activated amides for site-selective modification of peptides (Scheme 1B). Functionalization strategies include oxidation to the corresponding azole , reduction to the amine , modification of the amide nitrogen with electrophilic reagents, enolization of the C2 exocyclic position, and substitution at both C2 and C5 with nucleophilic reagents. Because incorporation of azolines can be a valuable method to activate amides, which is often difficult to achieve due to the low reactivity of the amide functional group, several synthetic strategies are known. Azole and azoline containing natural products are often derived from peptides, and their biosynthesis involves selective dehydrative cyclization of cysteine, serine, or threonine residues. In chemical synthesis, the oxazoline/thiazoline groups are introduced from 1,2-amino alcohols/thiols as the cyclization substrates through condensation of cysteine with nitriles, oxyamination of alkenes, and electrophilic cyclodehydration with phosphorus-, sulfur-, and Ti(IV)based reagents. Among the available catalytic strategies, a biomimetic Mo(VI)-catalyzed cyclodehydration first published by Ishihara and coworkers stands out. The Mo(VI) catalysis is more attractive in chemical synthesis due to its high selectivity eliminating unproductive side reactions and tolerating a diverse range of functional groups. Additionally, the reaction Scheme 1. Azolines in natural products and applications in in target-oriented synthesis. is run under relatively mild conditions, the only byproduct is water, and the stereochemistry at the C5 position of threonine derived oxazolines can be conserved. Despite these advantages, however, many Mo(VI) catalysts become deactivated after a few hours and the catalysts can be poisoned by solvents, substrates, or products, which is likely caused by the coordination of the compounds to the electrophilic metal center. Our group previously reported 6-methylpicolinate (6-MePic) as an effective ligand in the Mo(VI) cyclization of cysteine derivatives. This system was applied in the total synthesis of micrococcin P1 and thiocillin I (Scheme 1C). In this study we discovered that the bidentate picolinic acid additives could produce a more stable pre-catalyst. However, the scope of this new catalytic system has not been investigated in the context of oxazoline synthesis and more complex substrates such as oligopeptides.