The novel antibiotic, pseudomonic acid, binds tightly to its target en
zyme, isoleucyl t-RNA synthetase. The C12 to C14 region of the molecul
e is though to bind to the isoleucine binding site of the enzyme. Semi
synthetic analogues in which functionality present in this region have
been systematically modified are reported here: all the derivatives p
repared showed weak enzyme binding.