α-hydroxybenzylphosphonate modified oligonucleotides: Synthesis, properties, and a novel route via monomer building blocks

Article abstract of DOI:10.1081/NCN-120022816

In general, α-hydroxybenzylphosphonate modified 2′ -deoxyadenosine-thymidine dimer building blocks 1, 2 are utilized for the incorporation into α-hydroxybenzylphosphonate pro-oligonucleotides. For a universal application of our pro-oligonucleotide concept

Full text of DOI:10.1081/NCN-120022816

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α-Hydroxybenzylphosphonate Modified
Oligonucleotides: Synthesis, Properties, and a Novel
Route via Monomer Building Blocks
Andreas Hohlfeld a & Chris Meier a b
a Institute of Organic Chemistry , University of Hamburg , Hamburg, Germany
b Institute of Organic Chemistry , University of Hamburg , Martin-Luther-King-Platz 6,
D-20146, Hamburg, Germany
Published online: 31 Aug 2006.
To cite this article: Andreas Hohlfeld & Chris Meier (2003) α-Hydroxybenzylphosphonate Modified Oligonucleotides: Synthesis,
Properties, and a Novel Route via Monomer Building Blocks, Nucleosides, Nucleotides and Nucleic Acids, 22:5-8, 1123-1125,
DOI: 10.1081/NCN-120022816
To link to this article: http://dx.doi.org/10.1081/NCN-120022816
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NUCLEOSIDES, NUCLEOTIDES & NUCLEIC ACIDS
Vol. 22, Nos. 5–8, pp. 1123–1125, 2003
a-Hydroxybenzylphosphonate Modified Oligonucleotides:
Synthesis, Properties, and a Novel Route via
Monomer Building Blocks
*
Andreas Hohlfeld and Chris Meier
Institute of Organic Chemistry, University of Hamburg,
Hamburg, Germany
ABSTRACT
In general, a-hydroxybenzylphosphonate modified 20-deoxyadenosine-thymidine
dimer building blocks 1, 2 are utilized for the incorporation into a-hydroxy-
benzylphosphonate pro-oligonucleotides. For a universal application of our
pro-oligonucleotide concept on biologically relevant oligonucleotides a route
for the synthesis of modified monomer building blocks 3 was developed and is
presented herein.
Key Words: Antisense pro-oligonucleotides; Hydroxybenzylphosphonate
modification; Building blocks; Phosphinamidites.
In previous studies, we presented that (T)15 oligonucleotides, containing the
a-hydroxybenzylphosphonate modification showed significant enhancement in the
stability towards 30- and 50-exonucleases (SVP and CSP) compared to the unmodified
*Correspondence: Chris Meier, Institute of Organic Chemistry, University of Hamburg,
Martin-Luther-King-Platz 6, D-20146 Hamburg, Germany; Fax: +49 404 2838 2495; E-mail:
chris.meier@chemie.uni hamburg.de.
1123
DOI: 10.1081/NCN-120022816
Copyright # 2003 by Marcel Dekker, Inc.
1525-7770 (Print); 1532-2335 (Online)
www.dekker.com

1124
Hohlfeld and Meier
Figure 1. Structures of dimer building blocks 1 and 2 and the monomer target structure 3.
oligonucleotide. Also, the observed Tm-values of the hybridized DNA and RNA
point to a possible application as antisense oligonucleotides.[1,2]
We synthesized dimer building blocks 1 and 2 (Fig. 1) for the incorporation into
an anti h-ras sequence (50-TATTCCGTCAT-30). With this concept of dimer building
blocks it is possible to determine the absolute configuration at the phosphorus center
Figure 2. Reaction sequence for the synthesis of monomer building blocks.

a-Hydroxybenzylphosphonate Modified Oligonucleotides
1125
of the resulting oligonucleotides and to study the possible effects on the activity as
antisense pro-oligonucleotides.
For a wide application as a potential antisense pro-oligonucleotide system, it is
necessary to find a synthetic way to prepare monomer building blocks 3, which
should be suitable for solid phase synthesis. For the synthesis of a-hydroxybenzyl-
phosphinamidites 3 (Fig. 1), the a-hydroxy-(2-nitrobenzyl)-phosphinic acid 4 was
synthesized by an acid catalyzed nucleophilic addition of hypophosphinic acid to
2-nitrobenzaldehyde. The hydroxy group was protected, e.g., by TBDPSCl, DHP
or enolether 5 (Fpmp precursor) resulting the phosphinic acids 6a–c. Esterification
of the protected phosphinic acid 6b was achieved using DCC as coupling agent or
by pivaloyl chloride activation, yielding the phosphinic acid esters 7a–c. Chlorina-
tion of the protected phosphinic ester 7b to the chlorophosphine 8 and following
transformation with diisopropylamine led to the protected (a-hydroxy-2-nitroben-
zyl)-(isopropyloxy)-phosphinamidite 9 (Fig. 2).
We developed a route to the novel a-hydroxybenzylphosphinamidites. With this
method it should be possible to synthesize a-hydroxybenzyl-nucleosyl-phosphinami-
dites 3 and in further work the synthesis of these modified monomer building blocks
as well as the synthesis of modified oligonucleotides will be presented.
REFERENCES
1. Mauritz, R.P.; Meier, C.; Uhlmann, E. Synthesis of 30,50-dithymidylyl-a-hydroxy-
phosphonate dimer building blocks for oligonucleotide synthesis—a new
pro-oligonucleotide approach. Nucleosides Nucleotides 1997, 16, 1209–1212.
2. Mauritz, R.P.; Meier, C. Fpmp-protected a-hydroxyphosphonate diesters for the
synthesis of pro-oligonucleotides. Nucleosides Nucleotides 1997, 16, 675–678.