Novel methylenephosphophosphonate analogues of mycophenolic adenine dinucleotide. Inhibition of inosine monophosphate dehydrogenase

Metal-free highly chemo-selective bisphosphorylation and deoxyphosphorylation of carboxylic acids

Carboxylic acids are readily available in both the natural and synthetic world. Their direct utilization for preparing organophosphorus compounds would greatly benefit the development of organophosphorus chemistry. In this manuscript, we describe a novel and practical phosphorylating reaction under transition metal-free reaction conditions that can selectively convert carboxylic acids into the P-C-O-P motif-containing compounds through bisphosphorylation, and the benzyl phosphorus compounds through deoxyphosphorylation. This strategy provides a new route for carboxylic acid conversion as the alkyl source, enabling highly efficient and practical synthesis of the corresponding value-added organophosphorus compounds with high chemo-selectivity and wide substrate scope, including the late modification of complex APIs (active pharmaceutical ingredients). Moreover, this reaction also indicates a new strategy for converting carboxylic acids into alkenes by coupling this work and the subsequent WHE reaction with ketones and aldehydes. We anticipate that this new mode of transforming carboxylic acids will find wide application in chemical synthesis.

Anti-Tumor Potential of IMP Dehydrogenase Inhibitors: A Century-Long Story

The purine nucleotides ATP and GTP are essential precursors to DNA and RNA synthesis and fundamental for energy metabolism. Although de novo purine nucleotide biosynthesis is increased in highly proliferating cells, such as malignant tumors, it is not clear if this is merely a secondary manifestation of increased cell proliferation. Suggestive of a direct causative effect includes evidence that, in some cancer types, the rate-limiting enzyme in de novo GTP biosynthesis, inosine monophosphate dehydrogenase (IMPDH), is upregulated and that the IMPDH inhibitor, mycophenolic acid (MPA), possesses anti-tumor activity. However, historically, enthusiasm for employing IMPDH inhibitors in cancer treatment has been mitigated by their adverse effects at high treatment doses and variable response. Recent advances in our understanding of the mechanistic role of IMPDH in tumorigenesis and cancer progression, as well as the development of IMPDH inhibitors with selective actions on GTP synthesis, have prompted a reappraisal of targeting this enzyme for anti-cancer treatment. In this review, we summarize the history of IMPDH inhibitors, the development of new inhibitors as anti-cancer drugs, and future directions and strategies to overcome existing challenges.

New conjugates of mycophenolic acid and their antiproliferative activity

The new conjugates of mycophenolic acid (MPA) were obtained in the reaction of N(6)-(ω-aminoalkyl)adenosines with MPA in the presence of EDCI as a coupling reagent. New compounds 4a-h were evaluated on leukemia cell line (Jurkat) and PBMC from healthy donors. Length of the linker influenced observed activity. The compound 4b possessing 1,3-diamine spacer exhibited the most promising results and can be considered to further investigations.

Synthesis of new α-aminophosphonate derivatives incorporating benzimidazole, theophylline and adenine nucleobases using l-cysteine functionalized magnetic nanoparticles (LCMNP) as magnetic reusable catalyst: evaluation of their anticancer properties

A new class of α-aminophosphonate derivatives incorporating benzimidazole, theophylline and adenine nucleobases were synthesized in a three-step process and the anticancer activities of selected ligands were evaluated.

Mycobacterium tuberculosis IMPDH in Complexes with Substrates, Products and Antitubercular Compounds

Tuberculosis (TB) remains a worldwide problem and the need for new drugs is increasingly more urgent with the emergence of multidrug- and extensively-drug resistant TB. Inosine 5’-monophosphate dehydrogenase 2 (IMPDH2) from Mycobacterium tuberculosis (Mtb) is an attractive drug target. The enzyme catalyzes the conversion of inosine 5’-monophosphate into xanthosine 5’-monophosphate with the concomitant reduction of NAD⁺ to NADH. This reaction controls flux into the guanine nucleotide pool. We report seventeen selective IMPDH inhibitors with antitubercular activity. The crystal structures of a deletion mutant of MtbIMPDH2 in the apo form and in complex with the product XMP and substrate NAD⁺ are determined. We also report the structures of complexes with IMP and three structurally distinct inhibitors, including two with antitubercular activity. These structures will greatly facilitate the development of MtbIMPDH2-targeted antibiotics.

Bis(sulfonamide) isosters of mycophenolic adenine dinucleotide analogues: inhibition of inosine monophosphate dehydrogenase

Synthesis of novel inhibitors of human IMP dehydrogenase is described. These inhibitors are isosteric methylenebis(sulfonamide) analogues 5-8 of earlier reported mycophenolic adenine methylenebis(phosphonate)s 1-3. The parent bis(phosphonate) 1 and its bis(sulfonamide) analogue 5 showed similar sub-micromolar inhibitory activity against IMPDH2 (K(i) approximately 0.2 microM). However, the bis(sulfonamide) analogues 6 and 8 substituted at the position 2 of adenine were approximately 3- to 10-fold less potent inhibitors of IMPDH2 (K(i)=0.3-0.4 microM) than the corresponding parent bis(phosphonate)s 2 and 3 (K(i)=0.04-0.11 microM), respectively.

Novel diadenosine polyphosphate analogs with oxymethylene bridges replacing oxygen in the polyphosphate chain: potential substrates and/or inhibitors of Ap4A hydrolases

Dinucleoside polyphosphates (Np(n)N's; where N and N' are nucleosides and n = 3-6 phosphate residues) are naturally occurring compounds that may act as signaling molecules. One of the most successful approaches to understand their biological functions has been through the use of Np(n)N' analogs. Here, we present the results of studies using novel diadenosine polyphosphate analogs, with an oxymethylene group replacing one or two bridging oxygen(s) in the polyphosphate chain. These have been tested as potential substrates and/or inhibitors of the symmetrically acting Ap(4)A hydrolase [bis(5'-nucleosyl)-tetraphosphatase (symmetrical); EC 3.6.1.41] from E. coli and of two asymmetrically acting Ap(4)A hydrolases [bis(5'-nucleosyl)-tetraphosphatase (asymmetrical); EC 3.6.1.17] from humans and narrow-leaved lupin. The six chemically synthesized analogs were: ApCH(2)OpOCH(2)pA (1), ApOCH(2)pCH(2)OpA (2), ApOpCH(2)OpOpA (3), ApCH(2)OpOpOCH(2)pA (4), ApOCH(2)pOpCH(2)OpA (5) and ApOpOCH(2)pCH(2)OpOpA (6). The eukaryotic asymmetrical Ap(4)A hydrolases degrade two compounds, 3 and 5, as anticipated in their design. Analog 3 was cleaved to AMP (pA) and beta,gamma-methyleneoxy-ATP (pOCH(2)pOpA), whereas hydrolysis of analog 5 gave two molecules of alpha,beta-oxymethylene ADP (pCH(2)OpA). The relative rates of hydrolysis of these analogs were estimated. Some of the novel nucleotides were moderately good inhibitors of the asymmetrical hydrolases, having K(i) values within the range of the K(m) for Ap(4)A. By contrast, none of the six analogs were good substrates or inhibitors of the bacterial symmetrical Ap(4)A hydrolase.

Probing binding requirements of type I and type II isoforms of inosine monophosphate dehydrogenase with adenine-modified nicotinamide adenine dinucleotide analogues

Novel tiazofurin adenine dinucleotide (TAD) analogues 25-33 containing a substituent at C2 of the adenine ring have been synthesized as inhibitors of the two isoforms of human IMP-dehydrogenase. The 2-ethyl TAD analogue 33 [Ki = 1 nM (type I), Ki = 14 nM (type II)] was found to be the most potent. It did not inhibit three other cellular dehydrogenases up to 50 microM. Mycophenolic adenine bis(phosphonate)s containing a 2-phenyl (37) or 2-ethyl group (38), were prepared as metabolically stable compounds, both nanomolar inhibitors. Compound 38 [Ki = 16 nM (type I), Ki = 38 nM (type II)] inhibited proliferation of leukemic K562 cells (IC50 = 1.1 microM) more potently than tiazofurin (IC50 = 12.4 microM) or mycophenolic acid (IC50 = 7.7 microM).

Methylenebis(sulfonamide) linked nicotinamide adenine dinucleotide analogue as an inosine monophosphate dehydrogenase inhibitor

A methylenebis(sulfonamide) linked NAD analogue has been designed to circumvent the metabolically unstable, ionic nature of the natural pyrophosphate linkage. This NAD analogue is assembled through two Mitsunobu reactions of a methylenebis(sulfonamide) linker with two protected nucleosides. A 2,4-dimethoxybenzyl group is used as a sulfonamide protective group, which allows facile removal under mildly acidic conditions. This NAD analogue inhibits IMPDH at low micromolar concentration.