Synthesis and pharmacological evaluation of a new class of peroxisome proliferator-activated receptor modulators

A series of 5-substituted 2-benzoylaminobenzoic acids has been synthesized and assayed for PPAR/γ activity. Both dual activators and selective PPARγ agonists have been identified. This class of compounds was shown to activate the PPARγ receptor through interaction with a novel binding site.     

Binding of beta-carbolines at 5-HT(2) serotonin receptors

A series of ring-substituted (i.e., methoxy and bromo) 3,4-dihydro- and 1,2,3,4-tetrahydro-β-carbolines was examined at 5-HT_2A and 5-HT_2C serotonin receptors. Whereas most of the methoxy-substituted derivatives typically displayed affinities similar to their unsubstituted parents, certain (particularly 8-substituted) bromo derivatives displayed enhanced affinity. A binding profile was obtained for selected β-carbolines.     

Structural studies on hairy region of pectic polysaccharide from campion Silene vulgaris (Oberna behen)

Using enzymic digestion with pectinase, controlled Smith degradation and NMR-spectroscopy, some structural features of the hairy region of pectic polysaccharide termed silenan SV from the aerial part of campion Silene vulgaris (Moench) Garke (Oberna behen (L.) Ikonn) were elucidated.

Silenan was subjected to enzymic digestion with pectinase to furnish the polysaccharide fraction (SVP). The contained residues of -galacturonic acid (43%), arabinose, galactose and rhamnose as main constituents. The backbone of the hairy region of silenan was found to consist of -1,4-galactopyranosyl uronic acid and 2-O-glycosylated rhamnopyranose residues. The side chains contained linear regions of residues of -1,5-linked arabinofuranose and β-1,3-, β-1,4-linked galactopyranose. Silenan SV and its fragment SVP were subjected to Smith degradation to give fractions SVS and SVPS. These contain the residues of terminal and 2-substituted -arabinofuranose as well as residues of terminal, 3-, and 2,3-substituted β-galactopyranose. In addition, NMR-spectral data confirmed that the residues of -rhamnopyranose 2-O-glycosylated with the residues of -1,4-galactopyranosyl uronic acid of the backbone occurred in the core of SVPS and, therefore, in the backbone of silenan SV.

On the basis of data obtained, the hairy regions of silenan were suggested to contain mainly the linear chains of β-1,3-, β-1,4-galactopyranan and -1,5-arabinofuranan. The chains of -1,5-linked arabinofuranose, β-1,3- and β-1,4-linked galactopyranose were shown to be involved in the side chains of the hairy region having branching points at 2,3-substituted β-galactopyranose residues.     

Hoogsteen vs. Watson-Crick base pairing: incorporation of 2-substituted adenine- and 7-deazaadenine 2'-deoxy-beta-D-ribonucleosides into oligonucleotides

Various 2-substituted 2'-deoxyadenosines and 7-deazaadenosines have been synthesized. The phosphonate building block 9 of 2-chloro-7-deaza-2'-deoxyadenosine (7-deazacladribine; 2) was prepared by 4,4'-dimethoxytritylation of the parent nucleoside (-->7), followed by protection of the amino function with a formamidine residue (-->8). The latter was reacted with PCl3/N-methylmorpholine/1,2,4-triazole to give compound 9. Moreover, 2-methoxy-2'-deoxyadenosine (2'-deoxyspongosine; 1b) was converted into the fully protected derivative 12, which was then transformed into the 2-cyanoethyl phosphoramidite 14. Also the 2-(trifluoromethyl)-substituted 2'-deoxyadenosines 19-21 were prepared by glycosylation of the chromophore 16 with the halogenose 17, followed by one-pot deprotection and nucleophilic displacement of the 6-Cl substituent. The new DNA building blocks 9 and 14 were used--together with formerly prepared cladribine derivative 4--for solid-phase synthesis of a series of oligodeoxyribonucleotides. These were studied with respect to their thermal stability as well as of the base pairing mode (Watson-Crick vs. Hoogsteen) of modified bases.     

Insecticidal sesquiterpene polyol ester from Celastrus angulatus

An insecticidal sesquiterpene polyol ester, angulatin A, was isolated from the root bark of Celastrus angulatus. Its structure was established as 1,2-diacetoxy-8β,15-diisobutyryloxy-9-benzoyloxy-4β, 6β-dihydroxydihydro-β-agarofuran by spectroscopic methods.     

Novel mechanism of inhibiting beta-lactamases by sulfonylation using beta-sultams

β-Sultams are the sulfonyl analogues of β-lactams and N-acyl β-sultams are novel inactivators of the class C β-lactamase of Enterobacter cloacae P99. The rates of inactivation show a similar pH-rate dependence as that exhibited by the β-lactam antibiotics and with ESIMS data it is suggested that β-sultams sulfonylate the active site serine residue to form a sulfonate ester.     

Design, synthesis and preliminary evaluation of novel 3′-Substituted carboxycyclopropylglycines as antagonists at group 2 metabotropic glutamate receptors

Two novel 3′-substituted carboxycylopropylglycines, (2S,1′S,2′S,3′R)-2-(3′-xanthenylmethyl-2′-carboxycyclopropyl)glycine (8a) and (2S,1′S,2′S,3′R)-2-(3′-xanthenylethyl-2′-carboxycyclopropyl)glycine (8b), were synthesized and evaluated as mGluR ligands. Compound 8b showed to be a potent group II antagonist with submicromolar activity.     

Solid-phase synthesis of peptidosulfonamide containing peptides derived from Leu-enkephalin

Using Boc or Fmoc-protected β-substituted aminoethanesulfonyl chlorides (2-substituted taurylchlorides) the solid-phase synthesis of dipeptidosulfonamides as well as peptidosulfonamide containing peptides derived from Leu-enkephalin is described. The binding activity of the peptidosulfonamide YGGFL derivatives is reported.     

Ultrasound-promoted palladium-catalyzed carbonyl allylation by allylic alcohols with tin(II) chloride in non-polar solvents

Heterogeneous ultrasound-promoted palladium-catalyzed carbonyl allylation by γ-substituted allylic alcohols with tin(II) chloride in non-polar solvents such as diethyl ether, diisopropyl ether and toluene was carried out stepwise (first, the formation of allylic tin intermediates by ultrasonication, followed by the allylation of aldehydes by the intermediates) to produce 1,4-disubstituted 3-buten-1-ols regioselectively in moderate yields. The regioselectivity (-selection) in the ultrasound-promoted reaction is the inverse of that (γ-selection) in the homogeneous palladiumcatalyzed carbonyl allylation in polar solvents such as 1,3-dimethyl-2-imidazolidinone, DMF, DMSO and ethylene glycol. The more bulky the γ-substituent, the higher is the -regioselectivity.     

Saponins from Albizzia lucida.

Three main saponins were isolated from the seeds of Albizzia lucida. Their structures were established by spectral analyses and chemical and enzymatic transformations as 3-O-[β- -xylopyranosyl(1→2)-- -arabinopyranosyl (1→6)] [β- -glucopyranosyl (1→2)] β- -glucopyranosyl echinocystic acid; 3-O-[- -arabinopyranosyl (1→6)][β- -glucopyranosyl (1→2)]-β- -glucopyranosyl echinocystic acid and 3-O-[β- -xylopyranosyl (1→2)-β- -fucopyranosyl (1→6)-2-acetamido-2-deoxy-β- -glucopyranosyl echinocystic acid, characterized as its methyl ester.     

Biotransformation of β-amino nitriles: the role of the N-protecting group

N-Tolylsulfonyl- and N-butyloxycarbonyl-protected β-amino nitriles were prepared to study the effect of the N-protecting group on the biotransformation of the β-amino nitriles to the corresponding β-amino amides and acids. The bioconversions were carried out by using whole cells of Rhodococcus sp. R312 and Rhodococcus erythropolis NCIMB 11540. The bioconversion products of five-membered carbocyclic nitriles were mainly the respective acids whereas the carbocyclic six-membered nitriles were accumulated at the stage of the amide. Benefits of the enzymatic compared with the chemical hydrolysis of β-amino nitriles are the mild reaction conditions for the transformation of the nitrile group in the presence of acid or base labile N-protecting groups. In the present work we concentrated on this chemoselectivity of the biotransformation rather than its potential enantioselectivity, which will be subject of future investigations. Thus, some new compounds were prepared: (±)-(2-cyano-cyclohexyl) carbamic acid tert-butyl ester (4a), (±)-(2-carbamoyl-cyclopentyl) carbamic acid tert-butyl ester (3b) and (±)-(2-carbamoyl-cyclohexyl) carbamic acid tert-butyl ester (4b).     

β-carrageenan: Isolation and characterization

β-Carrageenan, essentially devoid of ester sulfate, was isolated from the hot aqueous extracts of alkali-modified Eucheuma gelatinae, Eucheuma speciosa, and Endocladia muricatum by precipitating the more anionic moieties with a quaternary ammonium salt, isolating the fractions that did not precipitate, then treating these with an anion-exchange cellulose. The β-carrageenan was characterized by chemical analysis, optical rotation, and NMR. Gelling was found to be ion-independent, with T_g = 31–33°C and T_m = 63–70°C. Specific optical rotations of the isolated β-carrageenan samples were more positive than the κ-, λ-, and ι-carrageenans with which they were compared, while agarose, its stereoisomer, exhibited a negative specific rotation. Electrophoresis gels made from β-carrageenan were used to separate DNA fragments which exhibited faster migration than on an agarose gel of comparable concentration, indicating that β-carrageenan has a less restrictive pore structure.     

Synthesis of 5-Substituted 2′-Deoxyuridine-5′- Phosphonate Analogues and Evaluation of their Antiviral Activity

A small series of 5-(hetero)aryl-modified nucleoside phosphonates was synthesized via an 8-step procedure including a Wittig reaction and Suzuki–Miyaura coupling. An unanticipated anomerization during phosphonate deprotection allowed us to isolate both anomers of the 5-substituted 2′-deoxy-uridine phosphonates and assess their antiviral activity against a broad panel of viruses.     

Novel isosteric, isopolar phosphonate analogs of oligonucleotides: preparation and properties

A synthetic approach leading to novel-type modified oligothymidylates containing an isosteric, isopolar, enzyme-stable C3'-O-P-CH(2)-O-C4' phosphonate alternative to phosphodiester internucleotide bond was elaborated. The suitable monomers were prepared from 4'-phosphonomethoxy derivatives of alpha-L-threo and beta-D-erythro-2',5'-dideoxythymidine, which were considered interesting as structurally related to nucleoside 5'-monophosphates. The phosphotriester method was applied to the automated synthesis of both homooligomeric phosphonate 15-mer chains and alternating phosphonate-phosphate constructs. The fully modified homooligomers did not hybridize while homooligomers with alternating sequences containing alpha-L-threo-configured units (but not beta-D-erythro-) showed a significant decrease in T(m) values in comparison with natural dT(15). For a comparative study, phosphodiester 4'-CH(3)-substituted oligothymidylate was synthesized and physical studies (NMR, CD, MDS modeling) were undertaken to shed more light on the changes in conformational behavior arising from the chosen structural alterations.     

Highly fluorescent guanosine mimics for folding and energy transfer studies

Guanosines with substituents at the 8-position can provide useful fluorescent probes that effectively mimic guanine residues even in highly demanding model systems such as polymorphic G-quadruplexes and duplex DNA. Here, we report the synthesis and photophysical properties of a small family of 8-substituted-2′-deoxyguanosines that have been incorporated into the human telomeric repeat sequence using phosphoramidite chemistry. These include 8-(2-pyridyl)-2′-deoxyguanosine (2PyG), 8-(2-phenylethenyl)-2′-deoxyguanosine (StG) and 8-[2-(pyrid-4-yl)-ethenyl]-2′-deoxyguanosine (4PVG). On DNA folding and stability, 8-substituted guanosines can exhibit context-dependent effects but were better tolerated by G-quadruplex and duplex structures than pyrimidine mismatches. In contrast to previously reported fluorescent guanine analogs, 8-substituted guanosines exhibit similar or even higher quantum yields upon their incorporation into nucleic acids (Φ = 0.02–0.45). We have used these highly emissive probes to quantify energy transfer efficiencies from unmodified DNA nucleobases to 8-substituted guanosines. The resulting DNA-to-probe energy transfer efficiencies (η_t) are highly structure selective, with η_t(duplex) < η_t(single-strand) < η_t(G-quadruplex). These trends were independent of the exact structural features and thermal stabilities of the G-quadruplexes or duplexes containing them. The combination of efficient energy transfer, high probe quantum yield, and high molar extinction coefficient of the DNA provides a highly sensitive and reliable readout of G-quadruplex formation even in highly diluted sample solutions of 0.25 nM.     

The synthesis of three 4-substitutedbenzo[b]thiophene-2-carboxamidines as potent and selective inhibitors of urokinase

Efficient syntheses of structurally novel 4-substituted benzo[b]thiophene-2-carboxamidmes 1–3, which selectively inhibit urokinase-type plasminogen activator (uPA) with IC₅₀ values of 70–320 nM, are described. The key intermediate, methyl 4-iodobenzo[b]thiophene-2-carboxylate (7), is prepared from 3-fluoroiodobenzene in two steps in 70% overall yield via fluorine-directed metalation/formylation and subsequent thiophene annulation. Amidination of ester 7 gives the 320 nM inhibitor 1. Palladium-catalyzed arylacetylene and vinyl stannane couplings with ester 7 or 4-iodobenzo[b]thiophene-2-carbonitrile (16, derived from 7), respectively, followed by amidination leads to the more potent inhibitors 2 (IC₅₀ = 133 nM) and 3 (IC₅₀ = 70 nM). These compounds represent an important new class of synthetic uPA inhibitors, with carboxamidine 3 being the most potent selective inhibitor currently described in the literature.     

Testosterone metabolism and sexual behavior in the chick

A series of experiments was performed to study the behavioral and physiological activity of testosterone (T) metabolites which are produced by neural tissues of male chicks, i.e., mainly 5α- and 5β-dihydrotestosterone (5α-, 5β-DHT), 5α- and 5β-androstan-3α, 17β-diol (5α-,5β-diol), and 4-androstene-3,17-dione (Δ4). It was found that 5β-reduced androgens alone or in combination with estradiol stimulate juvenile copulation in the chick while they have no detectable effect on all somatic variables which are recorded (testicular weight, plasma LH) with the exception of comb size. On the contrary, comb size was increased by T, Δ4, 5α-DHT, and 5α-diol while testis growth was prevented by T and Δ4 only. There is a good correlation between the anatomical localization of the enzymatic activities which metabolize T and the hormonal dependence of the biological responses: The comb converts T into 5α-reduced compounds which affect comb growth. 5β-Reduction is high in the hypothalamus, a fact which can be related to the sensitivity of sexual behavior to 5β-reduced androgens. This suggests that T metabolism is a very important step in the expression of this hormone's physiological effects.     

Modulating cholesteryl ester transfer protein activity maintains efficient pre-��-HDL formation and increases reverse cholesterol transport

The mechanism by which cholesteryl ester transfer protein (CETP) activity affects HDL metabolism was investigated using agents that selectively target CETP (dalcetrapib, torcetrapib, anacetrapib). In contrast with torcetrapib and anacetrapib, dalcetrapib requires cysteine 13 to decrease CETP activity, measured as transfer of cholesteryl ester (CE) from HDL to LDL, and does not affect transfer of CE from HDL3 to HDL2. Only dalcetrapib induced a conformational change in CETP, when added to human plasma in vitro, also observed in vivo and correlated with CETP activity. CETP-induced pre-β-HDL formation in vitro in human plasma was unchanged by dalcetrapib ≤3 µM and increased at 10 µM. A dose-dependent inhibition of pre-β-HDL formation by torcetrapib and anacetrapib (0.1 to 10 µM) suggested that dalcetrapib modulates CETP activity. In hamsters injected with [³H]cholesterol-labeled autologous macrophages, and given dalcetrapib (100 mg twice daily), torcetrapib [30 mg once daily (QD)], or anacetrapib (30 mg QD), only dalcetrapib significantly increased fecal elimination of both [³H]neutral sterols and [³H]bile acids, whereas all compounds increased plasma HDL-[³H]cholesterol. These data suggest that modulation of CETP activity by dalcetrapib does not inhibit CETP-induced pre-β-HDL formation, which may be required to increase reverse cholesterol transport.     

Structural characterization of cold extracted fraction of soluble sulfated polysaccharide from red seaweed Gracilaria birdiae

Water soluble polysaccharide from Gracilaria birdiae cultivated along the northeast coast of Brazil was characterized by infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The composition of the polysaccharide in wt% was determined as: β-d-galp (50.3%), 3,6-anhydro--l-galp (40.5%) and --l-galp-6 sulfate (9.2%). The ratio of l/d units (β-d-galp units and 3,6-anhydro--l-galp + -l-galp-6 sulfate) is that of an ideal agarose. The sulfate content calculated by S% accounts for 6.4%. 1D and 2D NMR techniques were employed in order to assign the spin system of polysaccharide without partial degradation. The structure is composed of → 4-3,6-anhydro--l-galp (1 → 3)β-d-galp 1 → segments, with the possibility of a -l-galp unit substituted at the 6-position by sulfate ester.     

A malonic acid ester derivative of naringin in grapefruit

A malonic acid ester derivative of the flavanone naringin was abundant in the young leaves and fruits of grapefruit plants, but not in the mature leaves and fruits. After isolation, the structure of this compound was established as naringin 6″-malonate (naringenin 72″-O-- -rhamnosyl)-β- -glucoside 6″-malonate).