New phosphoramidites of RNA cleaving trisbenzimidazole catalysts: improved compatibility with oligonucleotide solid phase synthesis

Phosphoramidite building blocks of trisbenzimidazole catalysts can be attached in high yield to the 5' end of oligonucleotides and convert them into site-specific RNA cleavers.Previous amidites, however, are not fully compatible with all types of DNA synthesizers.In this study we have tested several linker structures and protective groups.Tosyl protected compounds with alkyl linkers no longer show the former problems and can be coupled like standard DNA amidites.Although deprotection conditions are harsher for tosyl than for Boc, they are tolerated by the majority of nucleosides.If required, it is also possible to replace the tosyl groups with Boc.