Dharmacon RNA synthesis chemistry is based on a novel protecting group scheme
A unique class of silyl ethers is used to protect the 5´-hydroxyl (5´-SIL) in combination with an acid-labile orthoester protecting group on the 2´-hydroxyl (2´-ACE). This set of protecting groups is then used with standard phosphoramidite solid-phase synthesis technology. The structures of the protected and functionalized ribonucleoside phosphoramidites currently in use are as illustrated in Figure 1.