Angewandte
Chemie
DOI: 10.1002/anie.201412283
Solid-Phase Synthesis
Synthesis of Well-Defined Adenosine Diphosphate Ribose
Oligomers**
Hans A. V. Kistemaker, Lucien N. Lameijer, Nico J. Meeuwenoord, Herman S. Overkleeft,
Gijsbert A. van der Marel,* and Dmitri V. Filippov*
Abstract: The post-translational modification of proteins that
is known as adenosine diphosphate ribosylation (ADPr)
regulates a wide variety of important biological processes,
such as DNA-damage repair and cellular metabolism. This
modification is also involved in carcinogenesis and the process
of aging. Therefore, a better understanding of the function of
ADP-ribosylation is crucial for the development of novel
therapeutics. To facilitate the elucidation of the biology of
ADPr, the availability of well-defined fragments of poly(ADP-
ribose) is essential. Herein we report a solid-phase synthetic
approach for the preparation of ADP-ribose oligomers of
exactly defined length. The methodology is exemplified by the
first reported synthesis of an ADP-ribose dimer and trimer.
PAR polymers are associated with a wide variety of biological
processes, including DNA-damage repair, mitosis, apoptosis,
[
2]
and transcription. Elucidation of these processes at a molec-
ular level requires the availability of sufficient amounts of
structurally well defined PAR oligomers. PAR polymers and
oligomers are currently prepared enzymatically, which leads
to nonhomogenous products with a broad distribution in
terms of their chain length and branching points. PAR
fragments of some homogeneity can be obtained only by
[
3]
multiple chromatographic purification steps. We thus con-
sidered the development of a completely chemical synthetic
procedure as the most promising, and perhaps only, approach
to the preparation of sufficient amounts of well-defined PAR
oligomers for biological and structural studies.
P
oly-ADP-ribosylation (PARylation) is a post-translational
For the development of an efficient synthetic route to
PAR oligomers, several hurdles have to be overcome. The
first requirement is a cis-selective (a-selective) ribosylation of
adenosine in which the primary hydroxy functionalities of the
reacting partners are orthogonally protected. Mikhailov et al.
reported the first synthesis of a-linked 2-O-ribosyladenosine;
however, orthogonality in the protecting-group pattern was
modification in which numerous ADP-ribose molecules are
transferred to an acceptor protein to form a poly(ADP-
ribose) (PAR) polymer (Scheme 1). The size of the PAR
chains can reach 400 units, and branching at the 2’-hydroxy
[1]
group of the ribose moiety occurs once every 20 to 50 units.
[
4a]
lacking. Our research group devised a synthetic route to an
a-linked 2-O-ribosyladenosine building block with the
[
4b]
desired orthogonal protection.
this process proved to be unsatisfactory. A new route is
However, scaling up of
[5]
presented herein. In this route, a Vorbrꢀggen-type reaction
is used to synthesize orthogonally protected 2-O-ribosylated
adenosine on a relatively large scale (4 mmol).
The next challenge in synthesizing PAR oligomers is the
introduction of pyrophosphate linkages in a molecule already
containing one or more pyrophosphate bonds. The only
reported method for such a transformation proved to be
[6]
unsuccessful in our hands. We therefore built upon our
phosphoramidite procedure for the solution synthesis of sugar
nucleotide pyrophosphates. We anticipated that the syn-
Scheme 1. Structure of linear PAR oligomers.
[7]
thesis of a pyrophosphate in the presence of preexisting
pyrophosphate(s) would be difficult in solution. The adapta-
tion of this method for pyrophosphate formation to a solid-
phase procedure was plausible, as exemplified by the syn-
thesis of nucleoside di- and triphosphates by Jessen and co-
workers. Herein we demonstrate the assembly of PAR
oligomers with a well-defined length by using the phosphory-
lated 2-O-ribosyladenosine phosphoramidite 10 as a building
block in an automated solid-phase process.
[
*] H. A. V. Kistemaker, L. N. Lameijer, N. J. Meeuwenoord,
Prof. Dr. H. S. Overkleeft, Prof. Dr. G. A. van der Marel,
Dr. D. V. Filippov
[
8]
Leiden Institute of Chemistry
Department of Bio-organic Synthesis, Leiden University
Einsteinweg 55, 2333 CC Leiden (The Netherlands)
E-mail: marel_g@lic.leidenuniv.nl
For the synthesis of 2-O-ribosyladenosine, we started out
with the condensation of commercially available 1,3,5-tri-O-
benzoylribose (2) and the N-phenyltrifluoroacetimidate
donor 1 (Scheme 2). The glycosylation reaction was fast,
completely a-selective, and could be performed on an 8 mmol
Homepage: http://biosyn.lic.leidenuniv.nl/
[
**] This research was financially supported by the Netherlands
Organization for Scientific Research (NWO).
[
9]
Angew. Chem. Int. Ed. 2015, 54, 1 – 5
ꢀ 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1
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