Ribosylation of adenosine: an orthogonally protected building block for the synthesis of ADP-ribosyl oligomers

Solid-Phase Synthesis and Biological Evaluation of Peptides ADP-Ribosylated at Histidine

The transfer of an adenosine diphosphate (ADP) ribose moiety to a nucleophilic side chain by consumption of nicotinamide adenine dinucleotide is referred to as ADP-ribosylation, which allows for the spatiotemporal regulation of vital processes such as apoptosis and DNA repair. Recent mass-spectrometry based analyses of the "ADP-ribosylome" have identified histidine as ADP-ribose acceptor site. In order to study this modification, a fully synthetic strategy towards α-configured N(τ)- and N(π)-ADP-ribosylated histidine-containing peptides has been developed. Ribofuranosylated histidine building blocks were obtained via Mukaiyama-type glycosylation and the building blocks were integrated into an ADP-ribosylome derived peptide sequence using fluorenylmethyloxycarbonyl (Fmoc)-based solid-phase peptide synthesis. On-resin installation of the ADP moiety was achieved using phosphoramidite chemistry, and global deprotection provided the desired ADP-ribosylated oligopeptides. The stability under various chemical conditions and resistance against (ADP-ribosyl) hydrolase-mediated degradation has been investigated to reveal that the constructs are stable under various chemical conditions and non-degradable by any of the known ADP-ribosylhydrolases.

Solid-Phase Synthesis and Biological Evaluation of Peptides ADP-Ribosylated at Histidine

The transfer of an adenosine diphosphate (ADP) ribose moiety to a nucleophilic side chain by consumption of nicotinamide adenine dinucleotide is referred to as ADP-ribosylation, which allows for the spatiotemporal regulation of vital processes such as apoptosis and DNA repair. Recent mass-spectrometry based analyses of the "ADP-ribosylome" have identified histidine as ADP-ribose acceptor site. In order to study this modification, a fully synthetic strategy towards α-configured N(τ)- and N(π)-ADP-ribosylated histidine-containing peptides has been developed. Ribofuranosylated histidine building blocks were obtained via Mukaiyama-type glycosylation and the building blocks were integrated into an ADP-ribosylome derived peptide sequence using fluorenylmethyloxycarbonyl (Fmoc)-based solid-phase peptide synthesis. On-resin installation of the ADP moiety was achieved using phosphoramidite chemistry, and global deprotection provided the desired ADP-ribosylated oligopeptides. The stability under various chemical conditions and resistance against (ADP-ribosyl) hydrolase-mediated degradation has been investigated to reveal that the constructs are stable under various chemical conditions and non-degradable by any of the known ADP-ribosylhydrolases.

Synthesis of Poly(ADP-ribose) Monomer Containing 2'-O-α-D-Ribofuranosyl Adenosine

In this article, the earlier reported procedure for the synthesis of 2'-O-β-D-ribofuranosyl nucleosides was extended to the synthesis of 2'-O-α-D-ribofuranosyl adenosine, a monomeric unit of poly(ADP-ribose). It consists in condensation of a small excess of 1-O-acetyl-2,3,5-tri-O-benzoyl-α,β-D-arabinofuranose activated with tin tetrachloride with 3',5'-O-tetra-isopropyldisiloxane-1,3-diyl-ribonucleosides in 1,2-dichloroethane. The following debenzoylation and silylation of arabinofuranosyl residue and inversion of configuration at C-2'' atom of arabinofuranosyl residue and final removal of silyl protective groups gave 2'-O-α-D-ribofuranosyl adenosine in overall 13% to 21% yield. © 2019 by John Wiley & Sons, Inc.

Chemical Tools to Study Protein ADP-Ribosylation

Post-translational modification of substrate proteins plays crucial roles in the regulation of their activity, cellular localization, and ability to be recognized by other proteins. One of those modifications involves the installment of adenosine-diphosphate-ribose (ADPr) onto nucleophilic side-chain groups of amino acid residues. This highly dynamic process is regulated by ADP-ribosyl transferases (ARTs) that install the ADPr-molecules on selected proteins and poly(ADP-ribosyl) glycohydrolases (PARGs) and (ADP-ribosyl)hydrolases (ARHs) that trim down and remove ADPr-chains. In this mini-review, the most recent advances in the chemical synthesis of ADPr-conjugates, poly-ADP-ribose, ADPr-peptides, and -proteins, and other tools to investigate ADPr-biology are discussed.

Chemical ADP-ribosylation: mono-ADPr-peptides and oligo-ADP-ribose

ADP-ribosylation is an important post-translational modification that plays a pivotal role in many cellular processes, including cell signaling, DNA repair, gene regulation and apoptosis. Although chemical synthesis of mono- or poly-ADP-ribosylated biomolecules is extremely difficult due to the challenges in regio- and stereoselective glycosylation, suitable protective group manipulations and pyrophosphate construction, synthetic procedures towards these bio-related targets have been reported in recent years. Chemically synthesized well-defined ADP-ribose derivatives serve as useful tools in biological experiments aimed to further elucidate native ADP-ribosylation. In this review, we will discuss the synthetic studies on mono-ADP-ribosylated proteins and oligo-ADP-ribose chains. Future possible synthetic targets and upcoming new methods for the synthesis of these molecules are also included.

Direct Dehydrative Glycosylation of C1-Alcohols

Due to the central role played by carbohydrates in a multitude of biological processes, there has been a sustained interest in developing effective glycosylation methods to enable more thorough investigation of their essential functions. Among the myriad technologies available for stereoselective glycoside bond formation, dehydrative glycosylation possesses a distinct advantage given the unique properties of C1-alcohols such as straightforward preparation, stability, and a general reactivity compatible with a diverse set of reaction conditions. In this Focus Review, a survey of direct dehydrative glycosylations of C1-alcohols is provided with an emphasis on recent achievements, pervading limitations, mechanistic insights, and applications in total synthesis.

Synthesis of glyceryl glycosides related to A-type prymnesin toxins

A suite of glycosylated glycerol derivatives representing various fragments of the glycosylated ichthyotoxins called prymnesins were chemically synthesised. Glycerol was used to represent a small fragment of the prymnesin backbone, and was glycosylated at the 2° position with the sugars currently reported to be present on prymnesin toxins. Neighbouring group participation was utilised to synthesise 1,2-trans-glycosides. SnCl2-promoted glycosylation with furanosyl fluorides gave 1,2-cis-furanosides with moderate stereocontrol, whilst TMSOTf promoted glycosylation with a furanosyl imidate gave a 1,2-cis-furanoside with good stereocontrol. The chemical synthesis of two larger glyceryl diglycoside fragments of prymnesin-1, glycosylated with α-ʟ-arabinopyranose and α-ᴅ-ribofuranose, is also described. As the stereochemistry of the prymnesin backbones at this region is undefined, both the 2R- and 2S- glycerol isomers were synthesised. The separated diastereoisomers were distinguished by comparing NOESY NMR with computational models.

Synthesis of ribosyl-ribosyl-adenosine-5',5'',5'''(triphosphate)-the naturally occurring branched fragment of poly(ADP ribose)

Poly-adenosine diphosphate ribose (PAR) is a branched biopolymer that occurs as a result of post-translational modification of proteins. In 1981 Miwa et al. determined the structure of enzymatically prepared branched PAR. We present the first synthesis of the same branched PAR fragment and have shown by NMR that the structure proposed by Miwa is correct.

Dehydrative glycosylation with cyclic phosphonium anhydrides

Cyclic phosphonium anhydrides generated from bis-phosphine oxides and trifluoromethanesulfonic anhydride are shown as general coupling reagents in a dehydrative glycosylation reaction of C1-hemiacetals. This reaction protocol is characterized by a broad substrate scope and high yields, including reactions of O-, C-, N-, and S-based nucleophiles with furanose, pyranose, and deoxysugar donors.

Poly(ADP-ribose): From chemical synthesis to drug design

Poly(ADP-ribose) (PAR) is an important biopolymer, which is involved in various life processes such as DNA repair and replication, modulation of chromatin structure, transcription, cell differentiation, and in pathogenesis of various diseases such as cancer, diabetes, ischemia and inflammations. PAR is the most electronegative biopolymer and this property is essential for its binding with a wide range of proteins. Understanding of PAR functions in cell on molecular level requires chemical synthesis of regular PAR oligomers. Recently developed methodologies for chemical synthesis of PAR oligomers, will facilitate the study of various cellular processes, involving PAR.

Poly(ADP-ribose)--a unique natural polymer structural features, biological role and approaches to the chemical synthesis

Poly(ADP-ribose) (PAR) is a natural polymer, taking part in numerous important cellular processes. Several enzymes are involved in biosynthesis and degradation of PAR. One of them, poly(ADP-ribose)polymerase-1 (PARP-1) is considered to be a perspective target for the design of new drugs, affecting PAR metabolism. The structure of PAR was established by enzymatic hydrolysis and further analysis of the products, but total chemical synthesis of PAR hasn't been described yet. Several approaches have been developed on the way to chemical synthesis of this unique biopolymer.

Branching of poly(ADP-ribose): Synthesis of the Core Motif

The synthesis of the core motif of branched poly(adenosine diphosphate ribose) (poly(ADPr)) is described, and structural analysis reasserted the proposed stereochemistry for branching. For the synthesis, a ribose trisaccharide was first constructed with only α-O-glycosidic linkages. Finally, the adenine nucleobase was introduced via a Vorbrüggen-type glycosylation reaction. The orthogonality of the selected protecting groups was demonstrated, allowing for the construction of branched poly(ADPr) oligomers in the near future.

Synthesis of dimeric ADP-ribose and its structure with human poly(ADP-ribose) glycohydrolase

Poly(ADP-ribosyl)ation is a common post-translational modification that mediates a wide variety of cellular processes including DNA damage repair, chromatin regulation, transcription, and apoptosis. The difficulty associated with accessing poly(ADP-ribose) (PAR) in a homogeneous form has been an impediment to understanding the interactions of PAR with poly(ADP-ribose) glycohydrolase (PARG) and other binding proteins. Here we describe the chemical synthesis of the ADP-ribose dimer, and we use this compound to obtain the first human PARG substrate-enzyme cocrystal structure. Chemical synthesis of PAR is an attractive alternative to traditional enzymatic synthesis and fractionation, allowing access to products such as dimeric ADP-ribose, which has been detected but never isolated from natural sources. Additionally, we describe the synthesis of an alkynylated dimer and demonstrate that this compound can be used to synthesize PAR probes including biotin and fluorophore-labeled compounds. The fluorescently labeled ADP-ribose dimer was then utilized in a general fluorescence polarization-based PAR-protein binding assay. Finally, we use intermediates of our synthesis to access various PAR fragments, and evaluation of these compounds as substrates for PARG reveals the minimal features for substrate recognition and enzymatic cleavage. Homogeneous PAR oligomers and unnatural variants produced from chemical synthesis will allow for further detailed structural and biochemical studies on the interaction of PAR with its many protein binding partners.

Synthesis of well-defined adenosine diphosphate ribose oligomers

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.

Disaccharide pyrimidine nucleosides and their derivatives: a novel group of cell-penetrating inhibitors of poly(ADP-ribose) polymerase 1

Nearly 30 synthetic nucleosides were tested with human recombinant poly(ADP-ribose) polymerase 1 as potential inhibitors of this enzyme. The most active compounds were some disaccharide analogues of thymidine: 3'-O-β-D-ribofuranosyl-5-iodo-dUrd (2d; IC₅₀ = 45 μM), 3'-O-β-D-ribofuranosyl-2'-deoxythymidine (2e; IC₅₀ = 38 μM), and 3'-O-β-D-ribofuranosyl-2'-deoxythymidine oxidized (4; IC₅₀ = 25 μM). These compounds also reduced H₂O₂-induced synthesis of poly(ADP-ribose) in cultured human ovarian carcinoma (SKOV-3) cells in a dose-dependent manner. Furthermore, compounds 2d or 2e until a concentration of 1 mM did not affect growth of SKOV-3 cells, whereas dialdehyde compound 4, as well as thymidine, exhibited a significant cytotoxicity.

Stereoselective ribosylation of amino acids

The glycosylation properties of ribofuranosyl N-phenyltrifluoroacetimidates toward carboxamide side chains of asparagine and glutamine were investigated. Conditions were found that promote nearly exclusive formation of the α-anomerically configured N-glycosides. The strategy allows for the synthesis of Fmoc-amino acids suitably modified for the preparation of ADP-ribosylated peptides. Furthermore, ribosylation of serine with these donors proved to be completely α-selective, and for the first time, α-ribosylated glutamic and aspartic acid, the naturally occurring sites for poly-ADP-ribosylation, were synthesized.