Synthesis of pentathymidylate using a 4-monomethoxytritylthio (MMTrS) group as a 5′-hydroxyl protecting group: toward oligonucleotide synthesis without acid treatment

A phosphoramidite unit having 4-monomethoxytritylthio as a new 5′-hydroxyl protecting group was prepared and employed in oligonucleotide synthesis. The new phosphoramidite enabled the synthesis of oligonucleotides without the use of acids such as TFA or DCA.