Synthesis of Altritol Nucleoside Phosphoramidites for Oligonucleotide Synthesis

This unit describes in detail the optimized preparations of altritol nucleoside phosphoramidite building blocks for oligonucleotide synthesis (aA, aG, aC, aU). d-Altritol nucleosides with adenine and uracil bases are obtained by nucleophilic opening of the epoxide ring of 1,5:2,3-dianhydro-4,6-O-benzylidene-d-allitol using the 1,8-diazabicyclo[5.4.0]undec-7-ene salts of the above-mentioned salts, while phase transfer catalysis (18-crown-6, K2CO3) is optimal for alkylation of 2-amino-6-chloropurine. The cytosine nucleoside is synthesized starting from the uracil congener. The 3'-hydroxyl function of hexitol sugar is protected with the benzoyl group. Curr. Protoc. Nucleic Acid Chem. 30:1.18.1-1.18.21. ? 2007 by John Wiley & Sons, Inc.