Properties of artificial cationic oligodiaminosaccharides and oligopeptides that bind to A-type oligonucleotide duplexes.

A critical strategy to improve the properties of oligonucleotide therapeutics is using cationic molecules as carriers. We developed artificial cationic molecules that bind to A-type oligonucleotide duplexes, such as siRNAs, in a stoichiometric ratio. In this study, we investigated the properties of oligo 2,6-diamino-D-galactoses (ODAGals) and L-2,4-diaminobutanoic acid oligomers (Dabs) and revealed their thermal and biological stabilization effects on A-type duplexes and their chemical stability. As a result, ODAGal and Dab with the same number of amino groups had the commensurate ability for the biological stabilization effect, whereas Dab enhanced the thermal stability of A-type duplexes more effectively than ODAGal.

Synthesis and properties of oligodiaminogalactoses that bind to A-type oligonucleotide duplexes.

Recently, double-stranded oligonucleotide therapeutics with A-type duplex structures such as short interfering RNAs have gained considerable attention. We have reported the synthesis of cationic oligosaccharides that selectively bind to A-type oligonucleotide duplexes. In particular, oligodiaminogalactose (ODAGal) has a strong stabilizing effect on A-type oligonucleotide duplexes. However, an efficient synthetic method has not been established for ODAGals and the properties of ODAGals have been investigated only up to 4mer. The most crucial problem of the synthesis was side reactions on a p-methoxybenzyl (PMB) protecting group of a 3-hydroxy group. In this paper, the benzyl (Bn) group was chosen as a protecting group of the 3-hydroxy group to suppress the side reactions on protecting groups, and the yields of glycosylation reactions were significantly improved. Moreover, optimization of the conditions for the deprotection of the Bn groups allowed the efficient synthesis of fully deprotected ODAGals, and ODAGal 5mer and 6mer were synthesized for the first time. In addition, we systematically investigated the effects of these ODAGals on the properties of several oligonucleotide duplexes. It was found that ODAGal 4-6mers stabilized the A-type oligonucleotide duplexes thermally and biologically, typically without their structural changes and the effect was notable with longer ODAGals.

Solid-phase synthesis of N-trichloroacetyl mannosamine 1-phosphate repeating units mimicking capsular polysaccharide derived from Neisseria meningitidis serotype A.

N-Trichloroacetyl analogs of N-acetylmannosamine 1-phosphate repeating units, which are found in capsular polysaccharides of Neisseria meningitidis serotype A, were successfully obtained via solid-phase synthesis using an oxazaphospholidine monomer. The introduction of the trichloroacetyl group into the amino group of mannosamine resulted in the stabilization of the reaction intermediates. Monosaccharide, disaccharide, and tetrasaccharide derivatives were obtained and isolated. This is the first example to demonstrate the synthesis of the N-acylated mannosamine 1-phosphate structure having no less than four phosphate linkages.