Neuraminidase, a key enzyme responsible for influenza virus propagation, has been used as a template for selective synthesis of small subsets of its own inhibitors from theoretically highly diverse ...dynamic combinatorial libraries. We show that the library building blocks, aldehydes and amines, form significant amounts of the library components resulting from their coupling by reductive amination only in the presence of the enzyme. The target amplifies the best hits at least 120-fold. The dynamic libraries synthesized and screened in such an in vitro virtual mode form the components that possess high inhibitory activity, as confirmed by enzyme assays with independently synthesized individual compounds.
New and potent inhibitors of neuraminidase, a key enzyme in the influenza virus activity, have been discovered in dynamic combinatorial libraries based on ketones and amines as building blocks. ...Selective synthesis of a number of inhibitors among multiple theoretically possible combinations of building blocks is driven by the presence of the target enzyme.
Catechins are the major group of bioactive flavanols in green tea and cacao. 17 glucansucrase-active strains were identified from a set of 41 lactic acid bacteria, which were able to glucosylate ...(+)-catechin in a non-natural acceptor reaction. In total cell free extracts of 12 Leuconostoc and 5 Weissella strains were active on catechin and also 8 cell fractions exhibited catechin glucosylation activity. Six enzymes were selected for further evaluation and enriched up to 37 fold in yields of at least 40%. Glucansucrase of L. citreum DSM 5577 was the most efficient biocatalyst for (+)-catechin transformation with conversions of >40% after 24 h. NMR analysis of the major reaction product confirmed the (+)-catechin-4′-O-α-d-glucoside. Only L. kimchi B-65337 produced a second catechin monoglucoside. Four out of six glucansucrases glucosylated esculetin and all enzymes were active on haematoxylin. Glucansucrases of L. citreum DSM 5577, L. kimchi B-65337 and W. beninensis DSM 22752 were the best suited biocatalysts with conversions of >30% for esculetin and >60% for haematoxylin. W. beninensis DSM 22752 glucansucrase produced 89% haematoxylin glucosides without process optimization. L. kimchi B-65337 and W. beninensis DSM 22752 synthesized >40% diglucosides with the bifunctional haematoxylin. NMR analysis of the purified esculetin products confirmed formation of the 6-O-α-d- and 7-O-α-d-glucosides. Also two haematoxylin monoglucosides were identified as the 9-O-α-d- and 3-O-α-d-glucosides.
Due to their pronounced bioactivity and limited availability from natural resources, metabolites of the soft coral Pseudopterogorgia elisabethae, such as erogorgiaene and the pseudopterosines, ...represent important target molecules for chemical synthesis. We have now developed a particularly short and efficient route towards these marine diterpenes exploiting an operationally convenient enantioselective cobalt‐catalyzed hydrovinylation as the chirogenic step. Other noteworthy C−C bond forming transformations include diastereoselective Lewis acid‐mediated cyclizations, a Suzuki coupling and a carbonyl ene reaction. Starting from 4‐methyl‐styrene the anti‐tubercular agent (+)‐erogorgiaene (>98 % ee) was prepared in only 7 steps with 46 % overall yield. In addition, the synthesis of the pseudopterosin A aglycone was achieved in 12 steps with 30 % overall yield and, surprisingly, was found to exhibit a similar anti‐inflammatory activity (inhibition of LPS‐induced NF‐κB activation) as a natural mixture of pseudopterosins A−D or iso‐pseudopterosin A, prepared by β‐D‐xylosylation of the synthetic aglycone.
Applied metal catalysis: Exploiting a practical protocol for the asymmetric hydrovinylation of stryrenes in the opening move, the stereoselective total synthesis of bioactive constituents of the soft coral pseudopterogorgia elisabethae was efficiently achieved in sequence of metal‐mediated steps to provide sufficient material for further biological investigations.
Twelve Leuconostoc and seven Weissella strains with extracellular glucansucrase activity were obtained from an analysis of 41 lactic acid bacteria. Culture supernatants of all glucansucrase positive ...strains catalyzed the glycosylation of caffeic acid with sucrose as donor substrate. Eighteen enzymes produced one major peak, which was identified as caffeic acid-4′-O-α-D-monoglucoside by LC-MS and NMR spectroscopy. Only W. beninensis DSM 22752 formed significant amounts of the corresponding 3´-O-α-D-monoglucoside. The Weissella strain and five Leuconostoc strains with high glycosylation activity were selected for further studies. All glucansucrases catalyzed the glycosylation of the catechol protocatechuic acid, a side-chain truncated analogue of caffeic acid. The Leuconostoc enzymes displayed a preference for the 4′-O-α-D isomer, while the DSM 22752 glucansucrase also produced the protocatechuic acid-3′-O-α-D-monoglucoside. Lower activities with non-catecholic caffeic acid derivatives and no activity with mono-methylated caffeic acid were observed with all glucansucrases. Time-course analyses confirmed that glucansucrase from L. citreum DSM 5577 was the most efficient biocatalyst for catechol glucosylation with yields of up to 74% caffeic acid glucosides after 24 h. The enzyme displayed a high regio-preference for the 4′-O-α-d-isomer and formed less than 10% oligoglucosides. Gel electrophoretic analysis and activity staining of the PEG-enriched enzyme showed a single protein band with a molecular mass of 171 kDa. The DSM 5577 glucansucrase was tolerant against the co-solvents dimethyl sulfoxide and ethanol. Kinetic analysis revealed a KM of 27.6 mM for caffeic acid and 31 mM for sucrose with kcat values of 131 s−1 and 438 s−1.
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•Nineteen glucansucrase positive Leuconostoc and Weissella strains accepted caffeic acid.•Caffeic acid-4′-O-α-D-monoglucoside was the main product.•Novel glucosides of structural analogues umbellic and protocatechuic acid were discovered.•Purified glucansucrase of L. citreum DSM 5577 produced caffeic acid glucosides in 74% yield.•The solvent tolerant enzyme possessed a KM of 27.6 mM and a kcat of 131 s−1.
Objective
Matrix metalloproteinases (MMPs) have long been considered excellent targets for osteoarthritis (OA) treatment. However, clinical utility of broad‐spectrum MMP inhibitors developed for this ...purpose has been restricted by dose‐limiting musculoskeletal side effects observed in humans. This study was undertaken to identify a new class of potent and selective MMP‐13 inhibitors that would provide histologic and clinical efficacy without musculoskeletal toxicity.
Methods
Selectivity assays were developed using catalytic domains of human MMPs. Freshly isolated bovine articular cartilage or human OA cartilage was used in in vitro cartilage degradation assays. The rat model of monoiodoacetate (MIA)–induced OA was implemented for assessing the effects of MMP‐13 inhibitors on cartilage degradation and joint pain. The surgical medial meniscus tear model in rats was used to evaluate the chondroprotective ability of MMP‐13 inhibitors in a chronic disease model of OA. The rat model of musculoskeletal side effects (MSS) was used to assess whether selective MMP‐13 inhibitors have the joint toxicity associated with broad‐spectrum MMP inhibitors.
Results
A number of non–hydroxamic acid–containing compounds that showed a high degree of potency for MMP‐13 and selectivity against other MMPs were designed and synthesized. Steady‐state kinetics experiments and Lineweaver‐Burk plot analysis of rate versus substrate concentration with one such compound, ALS 1‐0635, indicated linear, noncompetitive inhibition, and Dixon plot analysis from competition studies with a zinc chelator (acetoxyhydroxamic acid) and ALS 1‐0635 demonstrated nonexclusive binding. ALS 1‐0635 inhibited bovine articular cartilage degradation in a dose‐dependent manner (48.7% and 87.1% at 500 nM and 5,000 nM, respectively) and was effective in inhibiting interleukin‐1α– and oncostatin M–induced C1,C2 release in human OA cartilage cultures. ALS 1‐0635 modulated cartilage damage in the rat MIA model (mean ± SEM damage score 1.3 ± 0.3, versus 2.2 ± 0.4 in vehicle‐treated animals). Most significantly, when treated twice daily with oral ALS 1‐0635, rats with surgically induced medial meniscus tear exhibited histologic evidence of chondroprotection and reduced cartilage degeneration, without observable musculoskeletal toxicity.
Conclusion
The compounds investigated in this study represent a novel class of MMP‐13 inhibitors. They are mechanistically distinct from previously reported broad‐spectrum MMP inhibitors and do not exhibit the problems previously associated with these inhibitors, including selectivity, poor pharmacokinetics, and MSS liability. MMP‐13 inhibitors exert chondroprotective effects and can potentially modulate joint pain, and are, therefore, uniquely suited as potential disease‐modifying osteoarthritis drugs.
Oxidative cyclization of the pyrrole–imidazole alkaloids oroidin and sventrin in DMSO/TFA (1:1) yields oxazolines as intermediates. Overall, the double bond of oroidin is dioxygenated.
Oxidative ...cyclization of the pyrrole–imidazole alkaloids oroidin and sventrin in DMSO/TFA (1:1) yields oxazolines via nucleophilic attack of the carbonyl oxygen at the alkenyl double bond. Oxidation takes place in the benzylic position of the imidazole ring. On prolonged reaction times, the oxazoline ring is hydrolyzed yielding the corresponding ester of pyrrole-2-carboxylic acid containing a free amino group. Overall, the double bond of oroidin is dioxygenated.
We investigated the relationship between the structures of pyrrole-containing alkaloids from marine sponges of the genus Agelas and their capacity to deter feeding by the omnivorous Caribbean reef ...fish, Thalassoma bifasciatum. Seven natural products were assayed at volumetric concentrations of 1, 5, and 10 mg/ml: dispacamide A, keramadine, oroidin, midpacamide, 4,5-dibromopyrrole-2-carboxylic acid, 4,5-dibromopyrrole-2carboxamide, and racemic longamide A. We also assayed 14 structural analogs obtained mostly by chemical synthesis. Of the seven natural products, only rac-longamide A was not significantly deterrent at any of the assay concentrations. The pyrrole moiety was required for feeding inhibition activity, while the addition of the imidazole group enhanced this activity. Variously functionalized imidazoles lacking the pyrrole moiety were not deterrent. Combinations of the natural products appeared to have an additive effect on feeding inhibition; there was no evidence of synergy. Given their high concentrations in sponge tissue, dispacamide A and oroidin most probably serve as the primary chemical defenses of many Agelas sp., while minor compounds such as keramadine are not present in high enough concentrations to contribute much to chemical defense.PUBLICATION ABSTRACT
A novel synthesis of the pyrrole-imidazole alkaloid keramadine (
1) from the marine sponge
Agelas sp. is described. Regiocontrol is reached by the Pd-catalyzed alkynylation of ...1-benzenesulfonyl-4-iodoimidazole, followed by N-methylation employing trimethyloxonium tetrafluoroborate. Key step is the double hydrogenation of a 5-alkynyl-2-azidoimidazole which simultanously generates the (
Z)-double bond and the amino function of
1.
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