Investigations into the synthesis of a nucleotide dimer via mechanochemical phosphoramidite chemistry.

Liquid-assisted mechanochemistry as a versatile approach for the coupling of a nucleoside phosphoramidite with a 5'-OH partially protected nucleoside has been investigated. Noted advantages over reported methods were a simplified reaction protocol, a drastic reduction in the use of toxic solvents, the facilitation of mechanochemical reactions through the improved mixing of solid reagents, and low hydrolytic product formation.

Scalable syntheses of traceable ribosylated NAD+ precursors.

Nicotinamide adenine dinucleotide, NAD+, is an essential cofactor and substrate for many cellular enzymes. Its sustained intracellular levels have been linked to improved physiological end points in a range of metabolic diseases. Biosynthetic precursors to NAD+ include nicotinic acid, nicotinamide, the ribosylated parents and the phosphorylated form of the ribosylated parents. By combining solvent-assisted mechanochemistry and sealed reaction conditions, access to the ribosylated NAD+ precursors and to the isotopologues of NAD+ precursors was achieved in high yields and levels of purity. The latter is critical as it offers means to better trace biosynthetic pathways to NAD+, investigate the multifaceted roles of the intracellular NAD+ pools, and better exploit NAD+ biology.

Multisubstrate adduct inhibitors: drug design and biological tools.

In drug discovery, different methods exist to create new inhibitors possessing satisfactory biological activity. The multisubstrate adduct inhibitor (MAI) approach is one of these methods, which consists of a covalent combination between analogs of the substrate and the cofactor or of the multiple substrates used by the target enzyme. Adopted as the first line of investigation for many enzymes, this method has brought insights into the enzymatic mechanism, structure, and inhibitory requirements. In this review, the MAI approach, applied to different classes of enzyme, is reported from the point of view of biological activity.

beta-1,2,3-Triazolyl-nucleosides as nicotinamide riboside mimics.

The synthesis of a series of pyridine- and piperidine-substituted 1,2,3-triazolides linked to a riboside moiety is described. The presence of a triazolide substituent on the pyridine moiety permitted the facile reduction of the latter under mild hydrogenation conditions. These analogues were modelled as to define their similarity to nicotinamide riboside and quantify their ability to bind NAD-dependent protein deacetylases.

Investigation of acetyl migrations in furanosides.

Standard reaction conditions for the desilylation of acetylated furanoside (riboside, arabinoside and xyloside) derivatives facilitate acyl migration. Conditions which favour intramolecular and intermolecular mechanisms have been identified with intermolecular transesterifications taking place under mild basic conditions when intramolecular orthoester formations are disfavoured. In acetyl ribosides, acyl migration could be prevented when desilylation was catalysed by cerium ammonium nitrate.

Probing Aplysia californica adenosine 5'-diphosphate ribosyl cyclase for substrate binding requirements: design of potent inhibitors.

Readily synthesized nicotinamide adenine dinucleotide (NAD(+)) analogues have been used to investigate aspects of the cyclization of NAD(+) to cyclic adenosine 5'-O-diphosphate ribose (cADPR) catalyzed by the enzyme adenosine 5'-O-diphosphate (ADP) ribosyl cyclase and to produce the first potent inhibitors of this enzyme. In all cases, inhibition of Aplysia californica cyclase by various substrate analogues was found to be competitive while inhibition by nicotinamide exhibited mixed-behavior characteristics. Nicotinamide hypoxanthine dinucleotide (NHD(+)), nicotinamide guanine dinucleotide (NGD(+)), C1'-m-benzamide adenine dinucleotide (Bp(2)A), and C1'-m-benzamide nicotinamide dinucleotide (Bp(2)N) were found to be nanomolar potency inhibitors with inhibition constants of 70, 143, 189, and 201 nM, respectively. However, NHD(+) and NGD(+) are also known substrates and are slowly converted to cyclic products, thus preventing their further use as inhibitors. The symmetrical bis-nucleotides, bis-adenine dinucleotide (Ap(2)A), bis-hypoxanthine dinucleotide (Hp(2)H), and bis-nicotinamide dinucleotide (Np(2)N), exhibited micromolar competitive inhibition, with Ap(2)A displaying the greatest affinity for the enzyme. 2',3'-Di-O-acetyl nicotinamide adenine dinucleotide (AcONAD(+)) was not a substrate for the A. californica cyclase but also displayed some inhibition at a micromolar level. Finally, inhibition of the cyclase by adenosine 5'-O-diphosphate ribose (ADPR) and inosine 5'-O-diphosphate ribose (IDPR) was observed at millimolar concentration. The nicotinamide aromatic ring appears to be the optimal motif required for enzymatic recognition, while modifications of the 2'- and 3'-hydroxyls of the nicotinamide ribose seem to hamper binding to the enzyme. Stabilizing enzyme/inhibitor interactions and the inability of the enzyme to release unprocessed material are both considered to explain nanomolar inhibition. Recognition of inhibitors by other ADP ribosyl cyclases has also been investigated, and this study now provides the first potent nonhydrolyzable sea urchin ADP ribosyl cyclase and cADPR hydrolase inhibitor Bp(2)A, with inhibition observed at the micromolar and nanomolar level, respectively. The benzamide derivatives did not inhibit CD38 cyclase or hydrolase activity when NGD(+) was used as substrate. These results emphasize the difference between CD38 and other enzymes in which the cADPR cyclase activity predominates.

Benzylfumaric, benzylmaleic, and Z- and E-phenylitaconic acids: synthesis, characterization, and correlation with a metabolite generated by Azoarcus tolulyticus Tol-4 during anaerobic toluene degradation.

E-Phenylitaconic acid has been isolated as a metabolite generated by Azoarcus tolulyticus Tol-4 along with benzylsuccinic acid during anaerobic degradation of toluene. Strain Tol-4 converted 1 to 2% of toluene carbon to E-phenylitaconate and benzylsuccinate (10:1). The identification of E-phenylitaconic acid was based on 1H nuclear magnetic resonance (NMR) characterization of degradation products derived from 13C-labeled toluene followed by comparison of spectroscopic and chromatographic data for the isolated, unlabeled metabolite with those for chemically synthesized benzylfumaric acid, benzylmaleic acid, E-phenylitaconic acid, and Z-phenylitaconic acid. Spectroscopic comparisons included 1H NMR, 13C NMR, and nuclear overhauser effect correlations. High-pressure liquid chromatography (HPLC) retention times and HPLC coinjections with synthetic dioic acids provided another reliable line of evidence for structure assignment. The formation of E-phenylitaconic acid differs from previous reports of benzylfumaric acid generation along with benzylsuccinic acid during anaerobic microbial degradation of toluene. This has important implications relevant to elaboration of the metabolic route for anaerobic toluene degradation by strain Tol-4 and related organisms. Similar amounts of E-phenylitaconic acid were also produced by seven other strains of A. tolulyticus.