Preparation of DNA containing 5-hydroxymethyl-2'-deoxycytidine modification through phosphoramidites with TBDMS as 5-hydroxymethyl protecting group.

This unit describes procedures for preparation of two phosphoramidite building blocks III and IV, both containing a TBDMS as 5-CH(2)OH-protecting group. Phosphoramidites III and IV allow efficient incorporation of 5-hmC into DNA and a "one-step" deprotection procedure to cleanly remove all the protecting groups. A "two-step" deprotection strategy is compatible with ultramild DNA synthesis, which enables the synthesis of 5 hmC-containing DNA with additional modifications. Methods are also presented for their incorporation into oligonucleotides by solid-phase synthesis, subsequent deprotection, and HPLC analysis.