A facile synthesis of (+)/(−)-pentenomycin I and analogs,and their antimicrobial evaluation

This study reported a stereoselective synthesis of (+)/(+)-pentenomycin I in 4–5 steps through regioselective silylation, optical resolution and dihydroxylation, followed by an olefin formation, from a known racemic cyclopentenone prepared from 2-deoxy-d-glucose. We also accomplished the transformation of a common intermediate into a variety of analogs. In addition, the antimicrobial activities of the pentenomycin analogs were evaluated, which revealed important structural factors of pentenomycins for the antimicrobial activities.     

β,β-Difluoro analogs of α-oxo-β-phenylpropionic acid and phenylalanine

A simple three-step procedure converted the readily accessible (2-bromo-1,1-difluoroethyl)arenes (2) into α-aryl-α,α-difluoroacetaldehydes (1). Subsequent hydrocyanation, hydrolysis, oxidation and again hydrolysis afforded β-aryl-β,β-difluoro-α-oxopropionic acids (3). Reductive amination transformed the oxoacids 3 into a separable mixture of α-hydroxyacids 11 and racemic β,β-difluoro-β-phenylalanine derivatives (4). Enantiomerically pure β,β-difluorophenylalanine (l-4a) was obtained when α,α-difluoro-α-phenylacet-aldehyde (1a) was condensed with homochiral 1-phenylethylamine, hydrogen cyanide added to the resulting imine, the diastereomeric mixture thus produced hydrolyzed to the carboxamides (15) which were found to be separable by fractional crystallization or chromatography. The pK_a values of the β-aryl-β,β-difluoroalanines (4) were measured and biological profile of the latter probed. 3-(4-Chlorophenyl)-3,3-difluoro-2-oxopropionic acid (4c) proved to be a potent (K_i 27 μM) and selective inhibitor of arogenate dehydratase, a key enzyme catalyzing the last step of the phenylalanine biosynthesis.     

Design, synthesis and in vitro evaluation of a series thiazolidinediones analogs as PPAR modulators

A series of thiazolidinediones analogs,as PPAR modulators,were designed,synthesized and evaluated in vitro.     

Imploded bilirubins: synthesis and properties of 10-nor-mesobilirubin-XIIIα and analogs

Abstract  Six 10-nor-bilirubin analogs have been synthesized and investigated. Lacking the C(10) CH₂ group, these linear tetrapyrroles have a bipyrrole core rather than a dipyrrylmethane core and thus a different shape. Whereas the propionic acid groups of bilirubin are well engaged in intramolecular hydrogen bonding to the dipyrrinones, molecular modeling studies of the 10-nor-rubins predict that propionic acid chains are too short to engage the CO₂H hydrogen fully in intramolecular hydrogen bonding with the dipyrrinones. Butyric acid chains, however, can and do lead to a stabilized conformation with a bipyrrole dihedral angle of approximately 115°. Spectroscopic studies verify the predictions and vapor pressure osmometry indicates that the 10-nor-rubins with butyric acids are monomeric in CHCl₃. Graphical abstract  

Cα-Cβ chromophore bond dissociation in protonated tyrosine-methionine, methionine-tyrosine, tryptophan-methionine, methionine-tryptophan and their sulfoxide analogs

C(α)-C(β) chromophore bond dissociation in some selected methionine-containing dipeptides induced by UV photons is investigated. In methionine containing dipeptides with tryptophan as the UV chromophore, the tryptophan side chain is ejected either as an ion or as a neutral fragment while in dipeptides with tyrosine, the tyrosine side chain is lost only as a neutral fragment. Mechanisms responsible for these fragmentations are proposed based on measured branching ratios and fragmentation times, and on the results of DFT/B3-LYP calculations. It appears that the C(α)-C(β) bond cleavage is a non-statistical dissociation for the peptides containing tyrosine, and occurs after internal conversion for those with tryptophan. The proposed mechanisms are governed by the ionization potential of the aromatic side chain compared to that of the rest of the molecule, and by the proton affinity of the aromatic side chain compared to that of the methionine side chain. In tyrosine-containing peptides, the presence of oxygen on sulfur of methionine presumably reduces the ionization potential of the peptide backbone, facilitating the loss of the side chain as a neutral fragment. In tryptophan-containing peptides, the presence of oxygen on methionyl-sulfur expedites the transfer of the proton from the side chain to the sulfoxide, which facilitates the loss of the neutral side chain.     

A biosynthetically inspired synthesis of (−)-berkelic acid and analogs

We describe a complete account of our total synthesis and biological evaluation of (?)-berkelic acid and analogs. We delineate a synthetic strategy inspired by a potentially biomimetic union between the natural products spicifernin and pulvilloric acid. After defining optimal parameters, we executed a one-pot silver-mediated in situ dehydration of an isochroman lactol to methyl pulvillorate, the cycloisomerization of a spicifernin-like alkynol to the corresponding exocyclic enol ether, and a subsequent cycloaddition to deliver the tetracyclic core of berkelic acid. Our studies confirm that the original assigned berkelic acid structure is not stable and equilibrates into a mixture of 4 diastereomers, fully characterized by X-ray crystallography. In addition to berkelic acid, C22-epi-berkelic acid, and nor-berkelic acids, we synthesized C26-oxoberkelic acid analogs that were evaluated against human cancer cell lines. In contrast to data reported for natural berkelic acid, our synthetic material and analogs were found to be devoid of activity.     

Eleuthesides and their analogs: III. Reaction of Red-Al with γ,δ-epoxy nitriles

Oxiranyl-substituted cycloalkenecarbonitriles obtained by the Beckmann fragmentation of oximes derived from levoglucosenone adducts with 1,3-butadiene, isoprene, cyclohexadiene, and cyclopentadiene were subjected to Red-Al reduction with opening of the epoxide ring. The reactions with 1,3-butadiene, isoprene, and cyclohexadiene derivatives were accompanied by cyclopropane ring closure and reduction of the cyano group to aldehyde, whereas the cyclopentadiene derivative underwent hydrogenolysis of the oxirane fragment.     

Synthesis and biological investigation of the β-thiolactone and β-lactam analogs of tetrahydrolipstatin

The synthesis of β-thiolactone and β-lactam analogs of tetrahydrolipstatin is described from a common late-stage β-lactone derivative. These analogs, and a cis-disubstituted β-lactone analog of tetrahydrolipstatin, were screened for activity against porcine pancreatic lipase and for inhibition of cell growth of a panel of four human cancer lines.     

Synthesis,characterization, and crystal structure of 2′,2″-dihydroxy-3,3‴-bichalcone and its related chalcone–flavanone and biflavanone analogs

The synthesis of 3,3′-diformyl-1,1′-biphenyl 1 and its reaction in basic media with 2′-hydroxyacetophenone and paeonol, respectively, are described. The products, a bichalcone 2, it’s partially cyclized analog, a flavanone–chalcone 3 and the fully cyclized biflavanone 4, are reported as products for the first reaction, while only the chalcone 5 for the second. The crystalline and molecular structure, solved by X-ray diffraction analysis, for compounds 2 and 5 are also presented in this work.     

Interaction of 1-methylthio-3,3-dimethyl-3,4-dihydroisoquinoline with Β-dicarboxylic acids, Β-dicarbonyl compounds,and their analogs

1-Methylthio-3,3-dimethyl-3,4-dihydroisoquinoline interacts as an electrophile with -dicarbonyl compounds and their analogs to form products in which one or two hydrogen atoms of the -carbonyl compound are replaced by a 3,3-dimethy 1-3,4-dihydroisoquinolyl or 3,3-dimethyl-1,2,3,4-tetrahydroisoquinolylidene fragment.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1651–1654, December 1992.     

Kinetic studies on the aggregation behavior of phosphatidylcholines and their analogs

Phosphatidylcholines (Ln's) and their neutral analogs 1,2-diacyl-sn-glycerol-3-phospho-ric acid bromoethyl esters (Pn's) have been found to exhibit different aggregation behaviors brought about by hydrophobic-lipophilic interactions (HLI) by means of kinetic probe in MeOH-H2O binary aquiorganic systems. The effects of the structure and the environment on the interesting aggregation of the amphiphilic molecules are discussed.     

Synthesis and antibacterial activity of 4“-O-carbamoyl analogs of clarithromycin

<正>A series of novel 4"-O-carbamoyl analogs of clarithromycin were synthesized and evaluated for their in vitro antibacterial activity. All of the desired compounds showed excellent activity against erythromycin-susceptible S.pneumoniae.Particularly,4-fluorobenzyl carbamate 7a demonstrated potent activity against erythromycin-resistant S.pneumoniae encoded by the mef gene,and remarkably improved activity against erythromycin-resistant S.pneumoniae encoded by the erm gene,and the erm and mef genes.     

Enantiomeric separation of α-phenylethylamine and its analogs by mixed chiral and achiral stationary phase

A mixed stationary phase of modified β-cyclodextrin, 2,6-di-O-butyl-3-O-butyryl-β-cyclodextrin (phase A), and SE-54 (phase B) was used for enantiomeric separation of α-phenylethylami-ne, o,m,p-methyl and o,m,p-methoxy-substituted analogs. The composition of mixed phase was selected by comparison of each calculated amin(= (γm,i+1)/(γm,i))> the relative retention values of the most adjacent peaks, and γm,last, the relative retention values of the last eluting peak at each preselected ratio. Values of γm,i,α calculated by derived equations were in good agreement with the experimental results obtained with two specified mixed phases. All solutes investigated were almost baseline separated at a predicted composition of phase A and phase B in a single run within 18 minutes.     

Simple synthesis and separation of the diastereomers of α-thio analogs of ribo- and deoxyribo- di- and triphosphates

Nucleoside 5′-0-(1-thiodi-) and triphosphates can be obtained in yields of up to 45% directly from the nucleosides. Their diastereomers can be separated by preparative reversed phase chromatography.     

Synthesis characterization and evaluation of novel triazole based analogs as a acetylcholinesterase and α-glucosidase inhibitors

A series of novel triazole analogs (10a-k) bearing piperidine were synthesized in an aprotic solvent on the most effective pharmacophore with acetylcholinesterase (AChE) and α-glucosidase inhibitory activity. Triazole analogs (10a-k) were obtained in excellent yields (75–90 %) and characterized by EI-MS, IR, ¹³C NMR and ¹H NMR. The newly synthesized triazole analogs (10a-k) showed potent AChE inhibitory activity in the range of K_i = 0.0155 ± 1.25 µM to 0.557 ± 0.50 µM, IC₅₀ = 0.031 ± 0.85 to 0.537 ± 0.76 µM than Eserine (0.04 ± 0.001 µM) having strong electron-withdrawing fluorine group on the pyridine ring was recorded as a most potent inhibitor of AChE while (%) inhibition against α-glucosidase was ranging between 52.36 ± 1.67 to 85.35 ± 1.39. The kinetic study predicted that triazole analogs (10a-k) followed the un-competitive and mixed type of inhibition against AChE. In silico molecular docking was performed at the active site of the AChE co-crystal structure (PDB ID:1NEN). The results of molecular docking corelate will with the experimental findings.     

Facile synthesis of naturally occurring nor-lignans (±)-Machicendiol and its analogs

A facile synthesis of naturally occurring (±)-machicendiol and its analogs has been accomplished in moderate to good yield from 2-aryl-5-formly-7-methoxy-benzofurans through two simple, efficient approaches involving the application of Reformatsky reaction and Claisen condensation.     

Synthesis and structure—activity relationships of cyclopropane-containing analogs of pharmacologically active compounds

The review summarizes information on cyclopropane as an independent pharmacophore group and as a fragment for modification of pharmacological activity level of medicines used in practice. The advantages of a cyclopropane fragment over its bioisosteres are that, on the one hand, this fragment imposes conformational rigidity on the molecules of physiologically active compounds and, on the other hand, the replacement of acyclic terminal and “linker” groups with a cyclopropane fragment increases the metabolic stability of the target structures and extends the scope of their therapeutic action.     

¹¹C-labeled analogs of indomethacin esters and amides for brain cyclooxygenase-2 imaging: radiosynthesis, in vitro evaluation and in vivo characteristics in mice

There is great potential in the use of positron emission tomography (PET) and suitable radiotracers for the study of cyclooxygenase type 2 (COX-2) enzyme in living subjects. In the present study, we prepared and evaluated five 11C-labeled ester and amide analogs derived from indomethacin as potential PET imaging agents for the in vivo visualization of the brain COX-2 enzyme. Five 11C-labeled COX-2 inhibitors, with different lipophilicities and moderate COX-2 inhibitory activity, were prepared by treatment of the corresponding O-desmethyl precursors with [11C]methyl triflate and purified by HPLC (radiochemical yields of 55-71%, radiochemical purity of >93%, and the specific activities of 22-331 GBq/μmol). In mice, radioactivity in the brain for all radiotracers was low, with very low brain-to-blood ratios. A clear inverse relationship was observed between brain uptake at 1 min postinjection and the lipophilicity (experimental log P?.?) of the studied 11C-radiotracers. Pretreatment of mice with cyclosporine A to block P-glycoproteins caused a significant increase in brain uptake of radioactivity following injection of the 11C-radiotracer compared to control. HPLC analysis showed that each radiotracer was rapidly metabolized, and a few metabolites, which were more polar than the original radiotracers, were found in both plasma and brain. No specific binding of the tracers towards the COX-2 enzyme in the brain was clearly revealed by in vivo blocking study. Further structural refinement of the tracer agent is necessary for better enhancement of brain uptake and for sufficient metabolic stability.     

Aromaticity or non aromaticity in germanazenes? Theoretical studies on germanazenes, the N-cyano analogs and their carbodiimide isomers

Theoretical studies of germanazene rings [(Ge_II-NR)_2,3; R = H, Me, CN, Ph] have been performed at the DFT/B3LYP level. The fully optimized geometrical structures display four or six-membered planar rings of alternating germanium and nitrogen, in good agreement with the available X-ray experimental data. The hypothetical molecule (GeN-H)₂ presents only a small distortion from planarity. Although the planar conformation could indicate some degree of delocalization, the stabilization energy - estimated using the concept of homodesmotic reactions - indicates very little or no aromatic character in these molecules. The easy experimental formation of these germanazenes can be explained by di- (or tri-)merisation of the transient monomeric germylene-imine GeNR in its triplet state. When R = CN, in conformity with the experimental results, the most stable species is the isomeric carbodiimide form (GeNCN)_n, a result which is easily explained by the maximum spin density on the terminal nitrogen in the calculated monomer.     

Intramolecular O→Te and N→Te coordination bonds in molecules of β-tellurocyclohexenals and their nitrogen analogs

The structures of -tellurocyclohexenals and their nitrogen analogs, viz., -methyltellurocyclohexenal (6), -(4-ethoxyphenyltelluro)cyclohexenal (7), di(2-formylcyclohexen-1-yl) telluride (8), -(4-ethoxyphenyltelluro)cyclohexenylidene(4"-methylaniline) (9), -bromotellurenylcyclohexenylidene(4"-methylaniline) (10), and -bromotellurenylcyclohexenal (4-methylbenzoyl)hydrazone (11), were studied by X-ray diffraction analysis. Compounds 6—11 have a Z configuration at the double bond, which provides the formation of intramolecular OTe or NTe coordination bonds. The bonds about the Te atom have a T-shaped configuration. There is only one of two possible OTe coordination bonds in dialdehyde 8 and, consequently, this compound belongs to the 10-Te-3-tellurane structural type. Hydrazone 11 possesses both NTe and OTe intramolecular coordination bonds. Taking into account these interactions, the coordination polyhedron of the tellurium atom can be considered as a trigonal bipyramid. The intramolecular OTe or NTe coordination bond lengths in compounds 6 (2.692 ), 7 (2.657 ), 8 (2.657 ), and 9 (2.690 ) are 0.9—1.0 smaller than the sums of the van der Waals radii of the corresponding atoms. These bond lengths in compounds 10 (2.170 ) and 11 (2.203 ) are almost equal to the standard covalent bond length.