Synthesis and structure?Activity studies of some antitumor congeners ofL-canaline

The Mechanism of l-Canavanine Cytotoxicity: Arginyl tRNA Synthetase as a Novel Target for Anticancer Drug Discovery

There is a clear need for agents with novel mechanisms of action to provide new therapeutic approaches for the treatment of pancreatic cancer. Owing to its structural similarity to L-arginine, L-canavanine, the beta-oxa-analog of L-arginine, is a substrate for arginyl tRNA synthetase and is incorporated into nascent proteins in place of L-arginine. Although L-arginine and L-canavanine are structurally similar, the oxyguanidino group of L-canavanine is significantly less basic than the guanidino group of L-arginine. Consequently, L-canavanyl proteins lack the capacity to form crucial ionic interactions, resulting in altered protein structure and function, which leads to cellular death. Since L-canavanine is selectively sequestered by the pancreas, it may be especially useful as an adjuvant therapy in the treatment of pancreatic cancer. This novel mechanism of cytotoxicity forms the basis for the anticancer activity of L-canavanine and thus, arginyl tRNA synthetase may represent a novel target for the development of such therapeutic agents.

Protected aminooxyprolines for expedited library synthesis: application to Tsg101-directed proline-oxime containing peptides

The stereoselective synthesis of aminooxy-containing proline analogues bearing Fmoc/Boc or Fmoc/Mtt protection that renders them suitable for incorporation into peptides using Fmoc protocols is reported. Acid-catalyzed unmasking at the completion of peptide synthesis yields free aminooxy-functionalities for oxime formation through reaction with libraries of aldehydes. This allows post solid-phase diversification strategies that may facilitate structure-activity relationship studies.

The antiproliferative and immunotoxic effects of L-canavanine and L-canaline

L-Canavanine and its arginase-catalyzed metabolite, L-canaline, are two novel anticancer agents in development. Since the immunotoxic evaluation of agents in development is a critical component of the drug development process, the antiproliferative effects of L-canavanine and L-canaline were evaluated in vitro. Both L-canavanine and L-canaline were cytotoxic to peripheral blood mononucleocytes (PBMCs) in culture. Additionally, the mononucleocytes were concurrently exposed to either L-canavanine or L-canaline and each one of a series of compounds that may act as metabolic inhibitors of the action of L-canavanine and L-canaline (L-arginine, L-ornithine, D-arginine, L-lysine, L-homoarginine, putrescine, L-omega-nitro arginine methyl ester and L-citrulline). The capacity of these compounds to overcome the cytotoxic effects of L-canavanine or L-canaline was assessed in order to provide insight into the biochemical mechanisms that may underlie the toxicity of these two novel anticancer agents. The results of these studies suggest that the mechanism of L-canavanine toxicity is mediated through L-arginine-utilizing mechanisms and that the L-canavanine metabolite, L-canaline, is toxic to human PBMCs by disrupting polyamine biosynthesis. The elucidation of the biochemical mechanisms associated with the effects of L-canavanine and L-canaline on lymphoproliferation may be useful for maximizing the therapeutic effectiveness and minimizing the toxicity of these novel anticancer agents.