Solid-Phase Synthesis of Multiantennary Oligonucleotide Glycoconjugates Utilizing On-Support Oximation

A novel method for preparation of multivalent oligonucleotide glycoconjugates on a solid support has been described. A pentaerythritol-based phosphoramidite (1) bearing two masked aminooxy groups has been used as the key building block. After conventional chain assembly, the aminooxy functions have been deblocked by a hydrazinium acetate treatment and subsequently oximated with fully acetylated 4-oxobutyl α-d-mannopyranoside. The conjugates obtained have been shown to withstand standard ammonolytic deprotection and cleavage from the support. Four different oligonucleotide glycoconjugates containing two, four, or six α-d-mannopyranosyl units (12−15) have been prepared to demonstrate the applicability of the procedure. The glycosyl residues only moderately retards hybridization of the oligonucleotide moiety.