A novel universal linker (UnyLinker) molecule which has a conformationally rigid and chemically stable bridge head ring oxygen atom carrying a conventional 4,4′-dimethoxytrityl (DMT) and succinyl groups locked in a syn orientation has been developed to carry out oligonucleotide synthesis efficiently and smoothly. The geometry of the vicinal syn oxygen functionalized group allows fast and clean cleavage under standard aqueous ammonia deprotection conditions to afford high-quality oligonucleotides. No base modification is observed, based on the ion-pair HPLC−UV−MS (IP-HPLC−UV−MS) method with detection limit of <0.1%. A class of impurities formed by branching from the exocyclic amino group of nucleosides loaded onto a solid support has been eliminated by the use of this method. Examples demonstrating the versatile nature of this molecule are shown by syntheses of different chemistries such as 2′-deoxy, 2′-O-methyl, 2′-O-methoxyethyl, Lock nucleic acids (LNA), 2′-α-fluoro nucleic acids (FANA), conjugates such as 5′-phosphate monoester and biotin, and phosphate diester and phosphorothioate backbone modifications. This molecule was loaded onto several commercial solid supports and used in both gas-sparged and packed-bed automated DNA/RNA synthesizers. Large-scale syntheses (up to 700 mmol) of multiple phosphorothioate first- and second-generation antisense drugs on GE-Amersham’s OligoProcess synthesizer are demonstrated further, showing that this chemistry could be used for efficient synthesis of multiple oligonucleotide drugs using a single raw material, thereby eliminating a difficult to characterize nucleoside-loaded polymer matrix used as a starting material. A mechanism for deprotection and cleavage of the linker molecule to liberate the free oligonucleotide is proposed. Characterization of the cyclic byproduct formed during release of the oligonucleotide is presented. The exo-syn configuration of the dihydroxy structure of the UnyLinker molecule is conclusively established by X-ray crystallography studies. A novel method to remove the last traces of osmium used during the synthesis of the UnyLinker molecule to reach undetectable levels (<1 ppm) is also described.

We employed palladium-catalyzed coupling procedures for the synthesis of new C8-adenosine adducts of various arylamines (aniline, benzidine, 4-aminobiphenyl, and 2-aminofluorene).[reaction: see text]

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The impuritiy profiles of acetonitrile solutions of the four standard O-cyanoethyl-N,N-diisopropyl-phosphoramidites of 5'-O-dimethoxytrityl (DMT) protected deoxyribonucleosides (dG(ib), dA(bz), dC(bz), T) were analyzed by HPLC-MS. The solution stability of the phosphoramidites decreases in the order T, dC>dA>dG. After five weeks storage under inert gas atmosphere the amidite purity was reduced by 2% (T, dC), 6% (dA), and 39% (dG), respectively. The main degradation pathways involve hydrolysis, elimination of acrylonitrile and autocatalytic acrylonitrile-induced formation of cyanoethyl phosphonoamidates. Consequently, the rate of degradation is reduced by reducing the water concentration in solution with molecular sieves and by lowering the amidite concentration. Acid-catalyzed hydrolysis could also be reduced by addition of small amounts of base.

Polycyclic aromatic amines (arylamines) are a class of chemical carcinogens that are prevalent in environmental and industrial settings. They are metabolically activated to covalently bond to DNA, forming mutagenic adducts. In order to study the mechanisms of their toxicity, sensitive and selective quantitative LC/MS/MS detection methods were developed to measure the N-(adenin-8-yl)-benzidine adduct and N-(adenin-8-yl)-2-aminofluorene in total DNA extract samples. A novel synthetic method using a palladium catalyst was previously developed to prepare authentic and deuterated arylamine-adenine adducts to serve as standards. These standards were then used to develop an HPLC electrospray ionization tandem mass spectrometry, isotope dilution method. Sample detection limits in DNA samples were 22 pg on-column and 51 pg on-column for the N-(adenin-8-yl)-benzidine-and N-(adenin-8-yl)-2-aminofluorene-adenine adducts, respectively. This method has applications for the study of DNA adduct formation as a biological marker of exposure to carcinogens and for environmental and workplace monitoring of these aromatic amines. (J Am Soc Mass