The synthesis and biological testing of bacilysin analogues

A series of compounds based on the structure of bacilysin were synthesised and tested for antibacterial activity. The key steps in the syntheses are the coupling of an iodide to a diketopiperazine (DKP) and mono-lactim ether scaffold, respectively. The diastereoselectivity of the coupling reactions was dependant on the scaffold, with selectivity for DKP of about 4:1 and mono-lactim ether exceeding 98:2. Subsequent elaboration of the compounds to give open chain dipeptides and DKPs that mimic the structure of bacilysin but substitute the epoxy ketone for a saturated or unsaturated ketone is described. Overall yield from coupling to final product was between 5 and 21 %, with the yield of the saturated products notably higher. The open chain dipeptides demonstrated moderate antibacterial and antifungal activity.