Synthesis of novel monomeric and homodimeric cyanine dyes based on oxazolo[4,5-b]pyridinium and quinolinium end groups for nucleic acid detection

Twelve novel di-, tri- and tetracationic, monomeric and homodimeric monomethine cyanine dyes based on oxazolo [4,5-b]pyridinium and quinolinium end groups were synthesized by condensation of 4-methyl-2-methylmercapto-oxazolo [4,5-b]pyridinium methosulfate and 1-(omega-iodopropyl)-4-methylquinolinium or appropriate 1-(omega-bromoalkyl)-4-methylquinolinium compounds and subsequent quaternization with pyridine, 1-methyl-4-aza-l-azonia-bicyclo[2.2.2]octanium iodide, 4,4'-trimethylenebis(I-methylpiperidinium)methyl iodide, N,N,NN',N'-pentamethyl-1,3-propandiammonium iodide, or bisquaternization with N,N,N',N'-tetramethyl-1,3-propanediamine, 4,4'-trimethylenebis(l-methylpiperidine). All dyes absorb at 521-522 nm in methanol and have a high molar absorptivity of about 106 000 (monomeric dyes) and 240 000 L mol(-1) cm(-1) (homodimeric dyes). The products were characterized by H-1 NMR spectra and elemental analysis. In the presence of nucleic acid a strong enhancement of the fluorescence was observed. (c) 2004 Elsevier Ltd. All rights reserved.