Improved phosphoramidite building blocks for the synthesis of the simplified nucleic acid GNA.

An improved synthesis of glycol nucleic acids is reported using new phosphoramidite building blocks in which the exocyclic amino groups of adenine and guanine are protected as N-dimethylformamidines, whereas the amino group of cytosine is protected via an acetamide. Besides a more rapid synthesis with higher yields, these phosphoramidites allow the use of a quicker deprotection procedure in the subsequent solid-phase synthesis of GNA oligonucleotides.