novel orthoesters are provided which can be used as a 2 ′- hydroxyl protecting groups or 2 ′- modification in the synthesis of polymers containing ribonucleic acid nucleotides . the rna comprising the orthoester can be handled and analyzed while 2 ′- modified , thereby minimizing potential degradation . the orthoester is stable during oligonucleotide synthesis . the orthoester is subsequently modified and can then be removed under mild acidic conditions . the ease and dependability of this process and the quality of the rna product synthesized with this invention are comparable to that previously associated only with dna synthesis .