RNA synthesis using monomers containing the 2'-O-TriisopropylsilylOxyMethyl (TOM) group (TOM-Protecting-Group™) is characterized by very high coupling efficiency along with fast, simple deprotection. High coupling efficiency is achieved because the TOM-Protecting-Group exhibits lower steric hindrance than the 2'-O-t-butyldimethylsilyl (TBDMS) group used in our alternative RNA monomers. Fast and reliable deprotection is achieved using methylamine in ethanol/water at room temperature. A further feature of the TOM-Protecting-Group is that during basic steps it can not undergo 2' to 3' migration. This migration under basic conditions leads to non-biologically active 2'-5' linkages when using the TBDMS group. These features allow the TOM-Protected monomers to produce longer oligonucleotides. TOM-Protected RNA monomers are also fully compatible with minor bases with 2'-O-TBDMS protection.
