Synthesis of an ethidium nucleoside and its acyclic analog

The protected ethidium nucleosides 8-(3',5'-di-O-benzoyl-2'-deoxy-D-ribofuranosyl)-3-acetamido-5-ethyl-6-phenylphenanthridinium (5), 8-(3',5'-di-O-acetyl-2'-deoxy-D-ribofuranosyl)-3-acetamido-5-ethyl-6-phenyl-phenanthridinium (6), and the acyclic analog 8-[(3R)-1,3-dihydroxy-4-yl]-acetamido-3-amino-5-ethyl-6-phenyl-phenanthridinium (3) were prepared. Based on to their different stability, only the acyclic derivative 3 seems to be suitable for oligonucleotide synthesis. Furthermore, the acyclic ethidium nucleoside analog 3 exhibits comparable absorption and emission properties of the underivatized ethidium (1). (C) 2003 Elsevier Science Ltd. All rights reserved.