Novel base-labile protecting groups for 5'-hydroxyl protection in the synthesis of oligonucleotides.

The 6-(levulinyloxymethyl)-3-methoxy-2-nitrobenzoyl (LMM0NBz) and 2-(levulinyloxy-methyl)-5-methoxy-4-nitrobenzoyl (LMMpNBz) groups were developed as novel base-labile protection for the 5'-hydroxyl group in solid-phase oligonucleotide synthesis. A comparative study on the utility of LMMoNBz, LMMpNBz, and 2-(levulinyloxymethyl)-5-nitrobenzoyl (LMNBz) groups for the synthesis of oligodeoxyribonucleotides, and the synthesis of oligoribonucleotides using the LMMoNBz group in combination with the acid-labile 1-ethoxyethylk (EE) group to protect the 2'-hydroxyl group, are described.