Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
2001-01-18
2003-04-08
Wilson, James O. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C536S017200, C536S018500, C536S018600, C536S018700, C536S027300, C536S027600, C536S028530
Reexamination Certificate
active
06545134
ABSTRACT:
The present invention relates to a process for the preparation of a 3′,4′-cyclic acetal of a pentopyranosylnucleoside, in which a pentopyranosylnucleoside is reacted with an aldehyde, ketone, acetal or ketal under reduced pressure.
Pyranosylnucleic acids (p-NAs) structural types which are in general 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
). In this context, “nucleobases” are understood 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-RNA's derived from ribose were described for the first time by Eschenmoser et al. (see. S. Pitsch et al.,
Helv. Chim. Acta
76, 2161 (1993); S. Pitsch et al.,
Helv. Chim Acta
78, 1621 (1995);
Angew. Chem
. 108, 1619-1623 (1996)). They form exclusively so-called Watson-Crick-paired, i.e. purine/pyrimidine and purine/purine-paired, antiparallel, reversibly “melting”, quasi-linear and stable duplices. Homochiral p-RNA strands of the opposite chiral sense likewise pair controllably and are strictly nonhelical 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 which are 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. have for the first time prepared a p-RNA, as shown in FIG.
2
and illustrated below (see also S. Pitsch et al. (1993), supra).
In this context, a suitable protected nucleobase was reacted with the anomer mixture of the tetrabenzoylribopyranose by action of bis(trimethylsilyl)acetamide and a Lewis acid such as, for example, trimethylsilyl trifluoromethanesulfonate (analogously to Vorbrüggen, H. et al.,
Chem. Ber
. 114, 1234 (1981)). Under the action of a base (NaOH in THF/methanol/water in the case of the purines; saturated ammonia in MeOH in the case of the pyrimidines), the acyl protective groups were removed from the sugar, and the product was protected in the 3′,4′-position with p-anisaldehyde dimethyl acetal under acidic catalysis. The diastereomer mixture was acylated in the 2′-position, and the 3′,4′-methoxybenzylidene-protected 2′-benzoate was deacetalated by acidic treatment, e.g. with trifluoroacetic acid in methanol, and was reacted with dimethoxytrityl chloride. The 2′→3′ migration of the benzoate was initiated by treatment with p-nitrophenol/4-dimethylaminopyridine/triethyl-amine/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 repeated 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 w a s purified and desalted by means of HPLC.
The process described by Eschenmoser et al ., however, cannot be reproduced with the yields indicated and is thus hardly suitable for application on the industrial scale.
The object of the present invention was therefore to make available a process which makes possible preparation of pentopyranosylnucleosides on the industrial scale.
It has now surprisingly been found that the preparation of the 3′,4′-cyclic acetal of a pentopyranosylnucleoside which is an intermediate in the Eschenmoser synthesis only takes place in appreciable yields if the pentopyranosylnucleoside is reacted with an aldehyde or ketone or with an acetal or ketal under reduced pressure.
One subject of the present invention is therefore a process for the preparation of a 3′,4′-cyclic acetal of a pentopyranosylnucleoside, in which a pentopyranosyl-nucleoside is reacted with an aldehyde, ketone, acetal or ketal under reduced pressure.
The term reduced pressure is understood according to the present invention as meaning, in particular, a pressure of less than about 500 mbar, preferably of less than about 100 mbar, in particular of less than about 50 mbar, especially of about 30 mbar.
The aldehyde is, for example, formaldehyde, acetaldehyde, benzaldehyde or 4-methoxybenzaldehyde, the acetal is formaldehyde dimethyl acetal, acetaldehyde dimethyl acetal, benzaldehyde dimethyl acetal or 4-methoxybenzaldehyde dimethyl acetal, the ketone is acetone, cyclopentanone or cyclohexanone and the ketal is acetone dimethyl ketal, cyclopentanone dimethyl ketal, cyclohexanone dimethyl ketal or is in the form of 2-methoxypropene.
In a particular embodiment, the pentopyranosylnucleoside is purified before the reaction, for example on SiO
2
, preferably on SiO
2
in the form of silica gel. Purification on a silica gel chromatography column, for example, is suitable for this. A gradient of about 1-20% or about 5-15% of methanol in dichlormethane, for example, is suitable for the elution of the pentopyranosylnucleoside. It is particularly advantageous if the pentopyranosylnucleoside is neutralized before the purification, for example with a 1% strength hydrochloric acid solution or with solid ammonium chloride, and the solvents are optionally stripped off.
A suitable pentopyranosylnucleoside is in general a ribo-, arabino-, lyxo- or xylo-pyranosylnucleoside. Examples of suitable pentopyranosylnucleosides are a pentopyranosylpurine, -2,6-diaminopurine, -6-purinethiol, -pyridine, -pyrimidine, -adenosine, -guanosine, -isoguanosine, -6-thioguanosine, -xanthine, -hypo-xanthine, -thymidine, -cytosine, -isocytosine , -indole, -tryptamine, -N-phthaloyl-tryptamine, -uracil, -caffeine, -theobromine, -theophylline, -benzotriazole or -acridine.
By way of formula, the pentopyranosylnucleosides can be represented by the formula (I)
in which
R
1
is equal to H, OH or Hal where Hal is equal to Br or Cl,
R
2
, R
3
and R
4
independently of one another, identically or differently, are in each case H, Hal where Hal is equal to Br or Cl, NR
5
R
6
, OR
7
, SR
8
, ═O, C
n
H
2n+1
where n is an integer from 1-12, preferably 1-8, in particular 1-4, or (C
n
H
2n
)NR
10
, R
11
where R
10
, R
11
are equal to H, C
n
H
2n+1
or R
10
R
11
is a radical of the formula
in which R
12
, R
13
, R
14
and R
15
independently of one another, identically or differently, are in each case H, OR
7
, where R
7
has the meaning mentioned, or C
n
H
2n+1
, or C
n
H
2n+1
, where n has the abovementioned meaning, and
R
5
, R
6
, R
7
and R
8
independently of one another, identically or differently, are in each case H, C
n
H
2n+1
, or C
n
H
2n−1
, where n has the abovementioned meaning, —C(O)R
9
where R
9
is equal to a linear or branched, optionally substituted alkyl or aryl radical, preferably a phenyl radical,
X, Y and Z independently of one another, identically or differently, are in each case ═N—, ═C(R
16
)— or —N(R
17
Eschenmoser Albert
Pitsch Stefan
Wendeborn Sebastian
Nanogen Recognomics, GmbH.
O'Melveny & Myers LLP
Wilson James O.
LandOfFree
Method for the production of pentopyranosyl nucleosides does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for the production of pentopyranosyl nucleosides, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for the production of pentopyranosyl nucleosides will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3001730