Hiroaki Sawai

Nonenzymatic template-directed condensation of short-chained oligouridylates on a poly(A) template.

An oligouridylate with chain-length of more thanthree was condensed on a polyadenylate [poly(A)]template with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDAC) in imidazole buffer. The condensation reactionproceeds via the phosphorimidazolide of theoligouridylate as an intermediate. Pentauridylate[(pU)5] was converted to decauridylate[(pU)10] in 10% yield at 0 °C for 7 daysin the presence of the poly(A) template, while nocoupling product was obtained in the absence of thepoly(A) template. The resulting linkage of the(pU)10 was mainly 2′–5′ linkage.

Facile Post-Synthetic Derivatization of Oligodeoxynucleotide Containing 5-Methoxycarbonylmethyl-2′-Deoxyuridine

Abstract 5-Methoxycarbonylmetyl-2′-deoxyuridine residue was incorporated into oligoDNAs containing either an exclusive thymidine residue (dT) or all four natural deoxynucleoside residues (dA, dG, dC, dT) via a phosphoramidite method. The treatment of the fully protected oligomer bound to controlled pore glass (CPG), with a variety of polyamine resulted in the release of the oligomer from CPG and the incorporation of the polyamine at the 5-position of the uracil component, simultaneously and in good yields.

An Approach to Prebiotic Synthesis of α-Oligoribonucleotides and Description of Their Properties: Selective Advantage of β-RNA over α-RNA

Abstract. Oligomerization of α-adenosine 5′-phosphorimidazolide (α-ImpA) has been done in an aqueous solution using a uranyl-ion catalyst or a poly(U) template as a model process of prebiotic synthesis of RNA with α-glycosidic linkage. α-Oligoriboadenylates up to hexamer were formed from α-ImpA by the uranyl-ion catalyst. 3′-5′ Linkage was mainly formed in the oligomerization. The poly(U) template mediated the oligomerization of α-ImpA, but to a very low extent. The yield and chain length of the resulting α-oligomers were far lower than those of the corresponding β-oligomer formation under the same conditions. Physico-chemical properties of α-oligoriboadenylates are presented along with those of the corresponding β-oligoriboadenylates. The results indicate that β-RNA is more advantageous than α-RNA from the points of their synthesis and properties.

Helical Structure Formation Between Complementary Oligonucleotides. Minimum Chain Length Required for the Template-Directed Synthesis of Oligonucleotides

Helix formation between various combinations of 3‘–5’ linked oligoribouridylates and oligoriboadenylates from dimer to dodecamer has been studied to gain information on the chain-length requirement for the template-directed condensation of oligoribonucleotides. We have measured the helix formation under high oligoribonucleotide concentration in the presence of magnesium ion at 0–50°C by UV or CD, as many model processes of oligoribonucleotides replication have been carried out under such conditions. Adenylic acid, (pA), diadenylic acid, (pA)2, or triadenylic acid, (pA)3, forms a helix with poly(U) or oligo(U) with a chain length of more than eight. On the other hand, neither uridylic acid, (pU), nor diuridylic acid, (pU)2, can form a helix with oligo(A) or poly(A). Triuridylic acid, (pU)3, or the longer oligo(U) forms a helix with oligo(A) with a chain length of over six. The results suggest that a trimer is the minimum unit as an incorporating nucleotide for conducting any set of nonenzymatic template-directed synthesis, A→U and U→A, as the nonenzymatic template-directed condensation of oligoribonucleotides correlates well with the results of helix formation of complementary oligoribonucleotides. We have further found the partial helix formation between 2‘–5’ linked decauridylate, (pU)10, and pA or 2‘–5’ linked (pA)2 at 0 °C, which indicates the possibility of the template activity of long 2‘–5’ linked oligonucleotides for the nonenzymatic oligonucleotide synthesis.

Effect of Acridine with Various Linker Arms Attached to C5 Position of 2′-Deoxyuridine on the Stability of DNA/DNA and DNA/RNA Duplexes

Abstract Acridine-modified oligodeoxyribonucleotides (ODNs) at the C5-position of a 2′-deoxyuridine via different lengths of linker arms were synthesized. Reaction of 5-(N-aminoalkyl)carbamoylmethyl-2′-deoxyuridines with 9-phenoxyacridine gave the acridine-modified 2′-deoxyuridines which were incorporated into ODNs. The duplexes containing the acridine-modified strands and their complementary DNA or RNA were thermally more stable than that containing the unmodified strand. Thermal stability of the duplexes of the modified ODNs varied depending on the length of the linker arms. This paper is dedicated to the late Professor Tsujiaki Hata.

Multi-functionalization of oligodeoxynucleotide: a facile post-synthetic modification technique for the preparation of oligodeoxynucleotides with two different functional molecules

Treatment of the support-bound novel multi-functionalizable noligodeoxyribonucleotides bearing both 5-cyanomethoxycarbonylmethyl- and n5-methoxycarbonylmethyl-uridine with tyramine followed by ntris(2-aminoethyl)amine facilitated multi-functionalization of noligodeoxyribonucleotides having different amine molecules.

Synthesis of oligodeoxyribonucleotide bearing 2'-S-alkyl residue and its effect on the duplex stability.

Abstract 2′-Deoxy-2′-S-hexyluridine derivative was synthesized from 2,2′-anhydrouridine and 1-hexanethiol and incorporated into an oligodeoxyribonucleotide. The thermal stability of the duplexes formed by the 2′-S-hexyl modified ODN with either the complementary DNA or RNA strand was decreased compared to the unmodified counterparts.