The present invention is directed to RNA monomers comprising O-acetal levulinyl protecting groups at the 2′ and/or the 5′-hydroxy functionalities of the ribose moiety. Said monomers may be incorporated into oligoribonucleotides or RNA polynucleotides. Furthermore, the invention is directed to methods for the synthesis of said RNA monomers, oligoribonucleotides and RNA polynucleotides, as well as methods for their deprotection and methods for the use of said compounds and compositions comprising said compounds. In particular, such compounds and compositions comprising them are used in methods for light-directed synthesis of RNA microarrays.