Synthesis and Antiproliferative Activity Evaluation of the Disulfide-Containing Cyclic Peptide Thiochondrilline C and Derivatives

Thiochondrilline C (4) was previously isolated from Verrucisispora sp. and reported to have moderate cytotoxicity against human lung adenocarcinoma cells. Herein, we report the synthesis of thiochondrilline C by N-terminal peptide extension, oxidative disulfide bond formation, and heterocycle installation as key steps. Antiproliferative activities for the prepared natural product and several derivatives against the NCI 60 cancer cell line panel are also described. Derivative 22 was identified as a moderately potent antiproliferative agent (50% growth inhibition (GI(50)) = 0.2-12.2 mu M) with leukemia (average GI(50) = 1.8 +/- 0.1 mu M) and colon (average GI(50) = 2.4 +/- 0.3 mu M) cells being most sensitive.