Oligo Synthesis : CEPs

Stability in Solution: 2-3 days

methyl phosphoramidites

For many years, Glen Research has supplied methyl phosphoramiditesin addition to þ-cyanoethyl (CE) phosphoramidites for the few situations wherethe more labile cyanoethyl group is not an advantage. Some of our customers,probably remembering that the methyl group was removed specifically withthiophenol, have tried to use these monomers to prepare the interesting,uncharged, and nuclease-resistant methyl phosphotriester linkage. Unfortunately,this linkage is labile to ammonium hydroxide and the regular phosphodiesterlinkage is formed (along with a small amount of chain scission). Now we offerUltraMild methyl phosphoramidites for this application. Oligos produced fromthese monomers can be deprotected with potassium carbonate in methanol toproduce methyl phosphotriester linkages. Since these linkages are diastereomericand uncharged, the oligos may be hard to handle. Consequently, it is likely thatchimeras will be produced using these monomers along with the regular UltraMildCE phosphoramidites. If many dG residues are included in the oligonucleotide, werecommend the use of phenoxyacetic anhydride (PAc₂O) in Cap A. Thismodification removes the possibility of exchange of the isopropyl-phenoxyacetate(iPr-Pac) protecting group on the dG with acetate from the acetic anhydridecapping mix.