Methods towards the incorporation of metal carbonyl complexes into oligodeoxyribonucleotides

Joan Marie Dalla Riva Toma, Purdue University

Abstract

There has been considerable interest in the development of non-radioactively labeled oligodeoxyribonucleotides for use as (1) probes in molecular biology research, (2) medical diagnostic tools, and (3) agents for the investigation of protein/DNA interactions by various analytical techniques. Group VI transition metal carbonyl complexes exhibit extremely intense absorptions in their IR spectra in the 2150-1900 cm$\sp{-1}$ region due to terminal metal carbonyl linkages. Additionally, these signals fall into a region of absorption which excludes most organic molecules, including those of proteins and other biomolecules. Thus, we have anticipated that transition metal carbonyl complexes could serve as molecular markers of oligonucleotides in DNA diagnostic studies. Moreover, incorporation of electron rich metal carbonyl complexes into oligonucleotides could facilitate structural studies using X-ray crystallography and electron microscopy. We have investigated several routes toward the synthesis of transition-metal modified oligonucleotides. Reaction of oligonucleoside methyl phosphites generated in situ with pentacarbonyl$(\eta\sp2$-cis-cyclooctene)tungsten (0) produces (pentacarbonyl)tungsten (0) nucleoside methyl phosphites. This chemistry has been extended to the preparation of dimers using an automated DNA synthesizer. Diastereomeric complexes were separated using reverse-phase HPLC. Extension of the reaction to longer oligonucleotide chains was however unsuccessful. Reaction of oligonucleoside $\beta$-cyanoethyl phosphites with pentacarbonyl$(\eta\sp2$-cis-cyclooctene)tungsten (0) produces, upon basic workup, oligonucleoside (pentacarbonyl) tungstate$(-$1) complexes. These complexes appear to be stable to conditions commonly employed to construct oligonucleotides by the phosphoramidite methodology. Several methods were undertaken in order to introduce (pentacarbonyl)tungsten (0) triphenylphosphine derivatives into oligodeoxyribonucleotides. Included in this, was the introduction of a triphenylphosphine phosphoramidite derivative, which when linked to the 5$\sp\prime$-terminus of a support-modified thymidine, resulted in the production of a 5$\sp\prime$-tethered phosphine oxide derivative. $\beta$-cyanoethylphophonium salts and (pentacarbonyl)tungsten (0) phosphoramidite complexes were therefore employed as protected phosphine ligands. A final method for the introduction of metal carbonyl triaryl phosphine complexes into oligodeoxyribonucleotides included the synthesis of pentacarbonyl (N-(hydroxy-succidimidyl)-2-(diphenylphosphino)benzoate) tungsten (0). Reaction of this compound with a support-bound oligodeoxyribonucleotide possessing a tethered primary amine was envisioned to afford a stable metal carbonyl labeled oligodeoxyribonucleotide.

Degree

Ph.D.

Advisors

Bergstrom, Purdue University.

Subject Area

Organic chemistry|Molecular biology|Biochemistry

COinS