Cyclic peptide natural products are a valuable source of biologically active molecules for clinical and industrial use. Ribosomally synthesised and post-translationally modified peptides (RiPPs) are examples of such products (e.g., nisin, microcins and polytheonamides) and are attracting significant interest due to their leader peptide-directed biosynthesis (LDB). Such carrier protein-free peptide maturation machinery provides a much simpler system compared to non-ribosomal peptide synthesis while being capable of introducing similar modifications, for example side-chain crosslinks catalysed by cytochrome P450 enzymes(1, 2). Recently, a unique family of RiPPs named biarylitides has been revealed, which achieve a rare, crosslinked structure via P450 catalysed peptide maturation using a 2 amino acid leader peptide(3). Here, we present a chemoenzymatic approach, utilising both solid phase peptide synthesis and P450-mediated cyclisation, to access various novel biarylitide analogues in vitro. The results, quantified via high resolution mass spectrometry (HRMS), indicate the enzymatic tolerance and hence the utility of this system aswell as revealing the mechanistic basis for substrate recognition and reaction mechanism, which offers a route to pre-functionalised biaryl building blocks.