Preparation of 5′‐Silyl‐2′‐Orthoester Ribonucleosides for Use in Oligoribonucleotide Synthesis

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Abstract
The recent discovery that small interfering RNAs (siRNAs) induce gene suppression in mammalian cells has sparked tremendous interest in using siRNA‐based assays and high‐throughput screens to study gene function. As a result, research programs at leading academic and commercial institutions have become a substantial and rapidly growing market for synthetic RNA. Important considerations in synthesizing RNA for biological gene function studies are sequence integrity, purity, scalability, and resistance to nucleases; ease of chemical modification, deprotection, and handling; and cost. Of the well‐established RNA synthesis methods, 2′‐ACE chemistry is the only one that meets all of these criteria. 2′‐ACE technology employs a unique class of silyl ethers to protect the 5′‐hydroxyl, in combination with an acid‐labile orthoester protecting group on the 2′‐hydroxyl (2′‐ACE). 2′‐ACE‐protected phosphoramidite monomers are joined using standard solid‐phase technology to achieve RNA synthesis at efficiencies rivaling those for DNA. This unit describes the synthesis of standard 5′‐silyl‐2′‐ACE‐protected phosphoramidites.