Specificity of DNA alkylation by 1-(2-chloroethyl)-3-alkyl-3-acyltriazenes depends on the structure of the acyl group: kinetic and product studies

First Synthesis of 2′-Deoxyfluoropuromycin Analogues: Experimental Insight into the Mechanism of the Staudinger Reaction

The N(6),N(6)-dedimethyl-2'-deoxyfluoro analogue of puromycin (= 3'-deoxy-N(6),N(6)-dimethyl-3'-[O-methyltyrosylamido]adenosine), its 2',3'-regioisomer and a 3'-cytidyl-5'-(2'-deoxyfluoro)puromycyl dinucleotide analogue were synthesized following an approach involving i) the diastereospecific nitrite-assisted formation of a lyxo nucleosidic 2',3'-epoxide from an adenosine-2',3'-ditriflate derivative in a biphasic solvent mixture; ii) the regio- and stereoselective epoxide ring opening with sodium azide under mildly acidic aqueous conditions, iii) the stereospecific introduction of the fluor atom using DAST and iv) the reaction between the nucleosidyl or dinucleotidyl azide and an active ester of the N-protected amino acid using highly efficient solution conditions for the Staudinger-Vilarrasa coupling, to obtain the corresponding carboxamide directly from the in situ formed iminophosphorane. This coupling reaction furnished sterically quite demanding amides in 94 % isolated yields under very mild conditions and should therefore be of a more general value. Under certain reaction conditions we isolated (amino)acyltriazene derivatives from which dinitrogen was not eliminated. These secondary products are trapped and stabilized witnesses of the first intermediate of the Staudinger reaction, the phosphatriazenes (phosphazides, triazaphosphadienes) which usually eliminate dinitrogen in situ and rapidly rearrange into iminophosphoranes, unless they are derived from conjugated or sterically bulky azides and phosphines. The acyltriazenes could either be thermally decomposed or converted to the corresponding N-alkyl carboxamides through proton-assisted elimination of dinitrogen. All compounds were carefully characterized through MS spectrometry, (1)H, (19)F, (31)P and (13)C NMR spectroscopy.

Engineering 3-alkyltriazenes to block bcr-abl kinase: a novel strategy for the therapy of advanced bcr-abl expressing leukemias

Recently, within the framework of a new strategy termed "combi-targeting," we designed ZRCM5 to contain a 2-phenylaminopyrimidopyridine moiety targeted to bcr-abl kinase and a triazene tail capable of generating a methyldiazonium species upon hydrolysis. The ability of ZRCM5 to block tyrosine kinase activity was tested in a short 10 min exposure ELISA involving isolated bcr-abl kinase and Western blotting assays. The results showed that: (a) ZRCM5 was hydrolyzed with a half-life of 27 min in cell culture media, (b) it blocked bcr-abl autophosphorylation in promyeloblastic leukemia K562 cells in a dose-dependent manner (IC(50)=14.01 microM) and (c) it induced dose-dependent levels of DNA strand breaks. In contrast, temozolomide (TEM), a clinical DNA damaging triazene capable of generating, like ZRCM5, a methyldiazonium species, could neither block bcr-abl tyrosine kinase activity in isolated enzyme nor in whole cell autophosphorylation assays. In cells expressing varied levels of bcr-abl, ZRCM5 was consistently more potent than TEM. The significant potency of ZRCM5 against the leukemia cells was attributed to its ability to simultaneously to block bcr-abl and related DNA repair activity while inducing significant DNA lesions in bcr-abl expressing leukemia cells. Further studies are ongoing to increase the affinity of ZRCM5 with the purpose of further enhancing its potency in bcr-abl expressing cells.