Use of a pentopyranosyl nucleoside for producing an...

Details Use of a pentopyranosyl nucleoside for producing an... Use of a pentopyranosyl nucleoside for producing an...

2000-07-11

2003-01-14

McGarry, Sean (Department: 1635)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carbohydrates or derivatives

C435S006120, C435S088000, C435S091100, C435S091500, C536S001110, C536S023100, C536S025300, C536S026710

Reexamination Certificate

active

06506896

ABSTRACT:

The present invention relates to a pentopyranosylnucleoside of the formula (I) or of the formula (II)
its preparation and use for the production of an electronic component, in particular in the form of a diagnostic.
Pyranosylnucleic acids (p-NAs) are in general structural types which are isomeric to the natural RNA, in which the pentose units are present in the pyranose form and are repetitively linked by phosphodiester groups between the positions C-2′ and C-4′ (FIG.
1
). “Nucleobase” is understood here as meaning the canonical nucleobases A, T, U, C, G, but also the pairs isoguanine/isocytosine and 2,6-diaminopurine/xanthine and, within the meaning of the present invention, also other purines and pyrimidines. p-NAS, namely the p-RNAs derived from ribose, were described for the first time by Eschenmoser et al. (see Pitsch, S. et al. Helv. Chim. Acta 1993, 76, 2161; Pitsch, S. et al. Helv. Chim Acta 1995, 78, 1621; Angew. Chem. 1996, 108, 1619-1623). They exclusively form so-called Watson-Crick-paired, i.e. purine-pyrimidine- and purine-purine-paired, antiparallel, reversibly “melting”, quasi-linear and stable duplexes. Homochiral p-RNA strands of the opposite sense of chirality likewise pair controllably and are strictly non-helical in the duplex formed. This specificity, which is valuable for the construction of supramolecular units, is associated with the relatively low flexibility of the ribopyranose phosphate backbone and with the strong inclination of the base plane to the strand axis and the tendency resulting from this for intercatenary base stacking in the resulting duplex and can finally be attributed to the participation of a 2′,4′-cis-disubstituted ribopyranose ring in the construction of the backbone. These significantly better pairing properties make p-NAs pairing systems to be preferred compared with DNA and RNA for use in the construction of supramolecular units. They form a pairing system which is orthogonal to natural nucleic acids, i.e. they do not pair with the DNAs and RNAs occurring in the natural form, which is of importance, in particular, in the diagnostic field.
Eschenmoser et al. (1993, supra) has for the first time prepared a p-RNA, as shown in FIG.
2
and illustrated below.
In this context, a suitable protected nucleobase was reacted with the anomer mixture of the tetrabenzoylribopyranose by action of bis(trimethylsilyl)acetamide and of a Lewis acid such as, for example, trimethylsilyl trifluoromethanesulphonate (analogously to H. Vorbrüggen, K. Krolikiewicz, B. Bennua, Chem. Ber. 1981, 114, 1234). Under the action of base (NaOH in THF/methanol/water in the case of the purines; saturated ammonia in MeOH in the case of the pyrimidines), the acyl protected groups were removed from the sugar, and the product was protected in the 3′,4′-position under acidic catalysis with p-anisaldehyde dimethyl acetal. The diastereomer mixture was acylated in the 2′-position, and the 3′,4′-methoxybenzylidene-protected 2′-benzoate was deacetalized by acidic treatment, e.g. with trifluoro-acetic acid in methanol, and reacted with dimethoxytrityl chloride. The 2′→3′ migration of the benzoate was initiated by treatment with p-nitrophenol/4-(dimethylamino)pyridine/triethylamine/pyridine
-propanol. Almost all reactions were worked up by column chromatography. The key unit synthesized in this way, the 4′-DMT-3′-benzoyl-1′-nucleobase derivative of the ribopyranose, was then partly phosphitylated and bonded to a solid phase via a linker.
In the following automated oligonucleotide synthesis, the carrier-bonded component in the 4′-position was repeatedly acidically deprotected, a phosphoramidite was coupled on under the action of a coupling reagent, e.g. a tetrazole derivative, still free 4′-oxygen atoms were acetylated and the phosphorus atom was oxidized in order thus to obtain the oligomeric product. The residual protective groups were then removed, and the product was purified and desalted by means of HPLC.
The described process of Eschenmoser et al. (1993, supra), however, shows the following disadvantages:
1. The use of non-anomerically pure tetrabenzoylpentopyranoses (H. G. Fletcher, J. Am. Chem. Soc. 1955, 77, 5337) for the nucleosidation reaction with nucleobases reduces the yields of the final product owing to the necessity of rigorous chromatographic cuts in the following working steps.
2. With five reaction stages, starting from ribopyranoses which have a nucleobase in the 1′-position, up to the protected 3′-benzoates, the synthesis is very protracted and carrying-out on the industrial scale is barely possible. In addition to the high time outlay, the yields of monomer units obtained are low: 29% in the case of the purine unit adenine, 24% in the case of the pyrimidine unit uracil.
3. In the synthesis of the oligonucleotides, 5-(4-nitrophenyl)-1H-tetrazole is employed as a coupling reagent in the automated p-RNA synthesis. The concentration of this reagent in the solution of tetrazole in acetonitrile is in this case so high that the 5-(4-nitrophenyl)-1H-tetrazole regularly crystallizes out in the thin tubing of the synthesizer and the synthesis thus comes to a premature end. Moreover, it was observed that the oligomers were contaminated with 5-(4-nitrophenyl)-1H-tetrazole.
4. The described work-up of p-RNA oligonucleotides, especially the removal of the base-labile protective groups with hydrazine solution, is not always possible if there is a high thymidine fraction in the oligomers.
A biomolecule, e.g. DNA or RNA, can be used for non-covalent linking with another biomolecule, e.g. DNA or RNA, if both biomolecules contain sections which, as a result of complementary sequences of nucleobases, can bind to one another by formation of hydrogen bridges. Biomolecules of this type are used, for example, in analytical systems for signal amplification, where a DNA molecule whose sequence is to be analysed is on the one hand to be immobilized by means of such a non-covalent DNA linker on a solid support, and on the other hand is to be bonded to a signal-amplifying branched DNA molecule (bDNA) (see, for example, S. Urdea, Biol/Technol. 1994, 12, 926 or U.S. Pat. No. 5,624,802). An essential disadvantage of the last-described systems is that to date they are subject with respect to sensitivity to the processes for nucleic acid diagnosis by polymerase chain reaction (PCR) (K. Mullis, Methods Enzymol. 1987, 155, 335). This is to be attributed, inter alia, to the fact that the non-covalent bonding of the solid support to the DNA molecule to be analysed as well as the non-covalent bonding of the DNA molecule to be analysed does not always take place specifically, as a result of which a mixing of the functions “sequence recognition” and “non-covalent bonding” occurs.
The object of the present invention was therefore to provide novel biomolecules and a process for their preparation in which the above-described disadvantages can be avoided.
The use of p-NAs as an orthogonal pairing system which does not intervene in the DNA or RNA pairing process solves this problem advantageously, as a result of which the sensitivity of the analytical processes described can be markedly increased.
One subject of the present invention is therefore the use of pentopyranosylnucleotides or pentopyranosylnucleic acids preferably in the form of a conjugate comprising a pentopyranosylnucleotide or a pentopyranosylnucleic acid and a biomolecule for the production of an electronic component, in particular in the form of a diagnostic.
Conjugates within the meaning of the present invention are covalently bonded hybrids of p-NAs and other biomolecules, preferably a peptide, protein or a nucleic acid, for example an antibody or a functional moiety thereof or a DNA and/or RNA occurring in its natural form. Functional moieties of antibodies are, for example, Fv fragments (Skerra & Plückthun (1988) Science 240, 1038), single-chain Fv fragments (scFv; Bird et al. (1988), Science 242, 423; Huston

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