The role of side chains in Substituted Pyrrole derivatives towards antiproliferative activity

In the last years, the introduction of side chains in different molecular compounds takes increasing importance. As recently reported in literature, heterocyclic scaffolds with poor biological activity , if properly decorated with selected side chains, can improve their anticancer activity against a large spectrum of human tumor cell lines. For example, the annelated Pyrrolo[3,4-e]Pyrimidines and Pyrrolo[3,2-e]Pyrimidines, opportunely functionalized with a large number of side chains, showed a good increase in the antitumor activity with respect to the starting core structure. New compound thus obtained showed antiproliferative activity against all the human tumor cells, generally in the low micromolar concentration range (1). Furthermore, this increase in activity is confirmed in the new linear derivatives Thieno[3,2-d][1,2,3]Triazolo [1,5- α]Pyrimidines (2) and their angular isomer Thieno[2,3-e][1,2,3]Triazolo[1,5- α]Pyrimidines (3). Another confirmation is provided by the Indolo [3,2-e][1,2,3]Triazolo [1,5- α]Pyrimidines, that resulted inactive as antitumor agent, but when a functionalization with side chains takes place, the anticancer activity has interestingly appeared (4). Here, with the aim to explore the importance of the addition of side chains on smaller molecular scaffolds, of easier synthetic access and decoration, we focused our attention on a new series of substituted “chained” pyrrole derivatives in order to evaluate their anticancer potential.