Antisense oligonucleotides: efficient synthesis of 2'-O-methoxyethyl phosphorothioate oligonucleotides using
Zhiwei Wang1, Andy Siwkowski, Walt F Lima
1Isis Pharmaceuticals, Inc., 2282 Faraday Avenue, Carlsbad, CA 92008, USA.
Abstract:
Multiple 2'-O-methoxyethyl modified phosphorothioate oligonucleotides of 18-20-mer in length were synthesized at various scales using 4,5-dicyanoimidazole (DCI) as coupling activator. Extensive synthetic, analytical (using ion-pair LC-MS), and in vivo pharmacological, toxicological studies showed that oligonucleotides made with DCI and 1H-tetrazole are chemically and biologically equivalent. This extensive study will help the oligonucleotide therapeutic industry to move from using a potentially explosive activator (1H-tetrazole) to a safe activator (DCI).
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