1-Ethynyl-dSpacer CE Phosphoramidite

1-Ethynyl-dSpacer CE Phosphoramidite can be used in any position within an oligonucleotide while still retaining the high efficiency of click chemistry. The modifier is efficiently incorporated into oligonucleotides using standard phosphoramidite chemistry, is stable to common deprotection conditions, and is compatible with Glen-Pak™ purification. 1-Ethynyl-dSpacer generates a substituted 1,2,3-triazole pseudo-nucleobase after click chemistry conjugation with an azide The 1-ethynyl-dSpacer modification exhibits similar duplex stability to the standard dSpacer (10-1914) and destabilizes the duplex when internally incorporated. Upon cycloaddition, the duplex stability is moderated by the resulting structure of the modification. Simple 1,2,3-triazoles were destabilizing, as were modifications that incorporated TEG linkers (6-FAM-TEG and Amino-TEG). Modifications that incorporated aromatic functional groups restored duplex stability to varying degrees with coumarin and psoralen significantly restoring stability. A 5’-iodo-modified oligonucleotide (prepared using 5’-Iodo-dT) can be quantitatively converted to the corresponding 5’-azide