What is the trityl-group?

Every DNA base (in terms of DNA synthesis chemistry, we are speaking of phosphoramidite monomers and amidites) added during DNA synthesis has a dimethoxy-trityl (trityl) protecting group attached to the 5´-hydroxyl position. This acid labile trityl-group is bound to the 5’-end of each support-bound monomer and protects the corresponding base from undergoing unwanted chemical reactions during the synthesis cycle. The trityl-group is removed in the first step of each synthesis cycle, immediately before a new base is added, until the elongation of the nucleotide chain is complete. The final trityl-group is removed before delivery (unless otherwise requested).