Various analogues of WF-3681 (1a), a novel aldose reductase inhibitor, were synthesized and examined for aldose reductase-inhibitory activity. It was found that the carboxylic acid function is necessary and the side-chain length is important for the activity. Furthermore, the lipophilicities of the benzene ring and the enol ether group are significant for increasing the activity.
Purpurealidin I (1) showed no selectivity but its simplified pyridin-2-yl derivative (36) had the best improvement in selectivity (Selectivity index 4.1). This shows that the marine bromotyrosines are promising scaffolds for developing cytotoxic agents and the full understanding of the elements of their SAR and improving the selectivity requires further optimization of simplified bromotyrosine derivatives.