Bruce S. Ross

A Novel and Economical Synthesis of 2″-O-Alkyl-Uridines

Abstract A highly efficient, two-step method to make 2′-O-methyluridine is described using only inexpensive reagents and no chromatography. The method is applicable for some other alkyls as well as some other pyrimidine derivatives.

KILO-SCALE SYNTHESIS PROCESS FOR 2′-O-(2-METHOXYETHYL)-PYRIMIDINE DERIVATIVES

We describe an improved process to produce 2′-O-(2-methoxyethyl)-pyrimidines. Starting with commercially available O-2,2′-anhydro-5-methyluridine and tris-(2-methoxyethyl)borate, we modified the ring-opening reaction conditions and changed to a continuous extraction purification method to give 2′-O-(2-methoxyethyl)-5-methyluridine. The dimethoxytritylation 5′/3′ ratios and yield were improved by the use of 2,6-lutidine as the base. Conditions to convert to the 5-methylcytidine analog and its isolation by crystallization were optimized. Final benzoylation was improved by developing a method to selectively hydrolyze benzoyl ester impurities.

Synthesis and Incorporation of 2′-O-Methyl-Pseudouridine into Oligonucleotides

Abstract A short multigram synthesis of 2′-O-methylpseudouridine and its phosphoramidite derivative is described which avoids the use of protecting groups on the nitrogens. A binding study of oligonucleotides containing this modification suggest an increased binding affinity to RNA when compared to oligonucleotides incorporating 2′-O-methyluridine.

2′- and 3′- Cholesterol-Conjugated Adenosine and Cytosine Nucleoside Building Blocks: Synthesis of Lipidic Nucleic Acids

Abstract Recently our laboratory introduced1 chemistries to synthesize 2′- and 3′- cholesteroluridine conjugates which were incorporated into several antisense oligonucleotides. We have now extended this chemistry to other nucleosides (adenosine and cytosine) and synthesized antisense oligonucleotide conjugates for several disease targets. Synthesis of these cholesterol nucleosides was carried out hy condensing choleskrol chloroformate with 2′-O-alkylamine or 3′-O-alkylamine of the appropriate nucleoside. The 2′-O-alkylamines were deiived from direct alkylation procedure.

An easy access of 2′,3′-dideoxy-3′-α-C-formyl-adenosine and -guanosine analogs via stereoselective CC bond forming radical reaction

Abstract A large-scale, facile and stereoselective synthesis of 1-[5- O -( tert -butyldiphenylsilyl)-2,3-dideoxy-3-α- C -formyl-β-D-erythro-pentofuranosyl] -adenine ( 7b ) and - N 2 -isobutyrylguanine ( 7c ) using an intermolecular radical CC bond formation reaction is reported. The utility of these nucleosides ( 7b and 7c ) as building blocks for antisense oligonucleosides is discussed.

Efficient large-scale synthesis of 5'-O-dimethoxytrityl-N4-benzoyl-5-methyl-2'-deoxycytidine.

An efficient process to synthesize 5′-O-dimethoxytrityl-N4-benzoyl-5-methyl-2 ′-deoxycytidine in high yield and quality is described. Final benzoylation was improved by developing a method to selectively hydrolyze benzoyl ester impurities. This inexpensive approach was scaled up to multi-kilogram quantities for routine use in oligonucleotide therapeutics.

An Efficient and Scalable Synthesis of Arabinosylguanine and 2′-Deoxy-2′-Fluoro-guanosine

Abstract An efficient conversion from commercially available 2, 6-diaminopurine-2′, 3′, 5′-tri-O-benzyl arabinoside to arabinosylguanine and its further transformation to 2′-deoxy-2′-fluoro-guanosine is outlined. This process has been used to produce more than one hundred grams of final product.

Process Research on the Preparation of DMT Protected 2′-O-Methoxyethylguanosine for Oligonucleotide Synthesis in Therapeutic Applications

An optimized process to synthesize DMT protected 2 ′-O-methoxyethylguanosine is described. A key step involves the enzymatic deamination of a mixture of alkylated products to selectively afford the desired material without resorting to chromatography for purification. This approach was scaled up to kilogram quantities for use in oligonucleotide therapeutics.

An efficient and scalable synthesis of 2,6-diaminopurine riboside.

An efficient process to synthesize 2,6-diaminopurine riboside in high yield and quality is described. This inexpensive approach was scaled up to multi-hundred kilogram quantities for use in oligonucleotide therapeutics.

A NEW PROTECTING GROUP STRATEGY FOR AMINO GROUPS IN OLIGONUCLEOTIDE CHEMISTRY : CEOC GROUP

Abstract A new protecting group, 2-cyanoethyloxycarbonyl, or CEOC, has been developed for amino groups and utilized in synthesizing modified oligonucleotides. (CEOC)-oxy-succinimide reagent has been synthesized to introduce this protecting group. The protecting group is removed by standard oligonucleotide deprotection protocols. Using this approach, oligonucleotides have been synthesized with various types of alkylamine substituents.