Nucleotides, Part LXIX, Synthesis of Phosphoramidite Building Blocks of IsoxanthopterinN8-(2′-Deoxy-β-D-ribonucleosides): New Fluorescence Markers for Oligonucleotide Synthesis

The chemical synthesis of isoxanthopterin and 6-phenylisoxanthopterin N8-(2′-deoxy-β-D-ribofuranosyl nucleosides) is described as well as their conversion into suitably protected 3′-phosphoramidite building blocks to be used as marker molecules for DNA synthesis. Applying the npe/npeoc (=2-(4-nitrophenyl)ethyl/[2-(4-nitrophenyl)ethoxy]carbonyl) strategy, we used the new building blocks in the preparation of oligonucleotides by an automated solid-support approach. The hybridization properties of a series of labelled oligomers were studied by UV-melting techniques. It was found that the newly synthesized markers only slightly interfered with the abilities of the labelled oligomers to form stable duplexes with complementary oligonucleotides.