Structural interpretation of the 31P NMR chemical shifts in thiophosphate and phosphate: key effects due to spin-orbit and explicit solvent.

Structural interpretation of the 31P NMR shifts measured in O,O-diethyl thiophosphate (PT), 5,5-dimethyl-2-mercapto-1,3,2-dioxaphosphorinane 2-oxide (cPT), diethylphosphate (P) and 5,5-dimethyl-2-hydroxy-1,3,2-dioxaphosphinane 2-oxide (cP) was obtained by means of theoretical calculations including the effects of geometry, molecular dynamics, and solvent, relativistic effects and the effect of NMR reference. NMR calculations employed the B3LYP, BP86, BPW91, M06-2X, PBE0, MP2, and HF methods, the Iglo-n (n = II, III), cc-pVnZ (n = D, T, Q, 5), and pcS-n (n = 0, 1, 2, 3, 4) Gaussian-type basis sets and the Slater-type QZ4P atomic basis. Water solvent was described explicitly and/or implicitly. The effects due to molecular dynamics were calculated using molecular dynamics simulations with the GAFF force field and the TIP3P water molecules, and alternatively by means of the zero-point ro-vibrational averaging. Relativistic effects included the spin-orbit calculated within the two-component zero-order relativistic approximation and the effect with the four-component DFT method. Optimal geometries and large-amplitude dynamical motions within the "opened" PT and P molecules contrasted with notably different geometries and confined dynamical motions within the cPT and cP "closed" molecules. These structure-dynamical differences together with the different chemical structures of thiophosphate and phosphate due to a non-esterified sulphur or oxygen atom within the group considerably affected the magnitudes of 31P NMR shifts. The theoretical calculations enabled accurate and reliable structure-dynamical interpretation of the measured 31P NMR shifts. The effects due to explicit solvent and relativity turned out to be indispensable for obtaining accurate 31P NMR shifts particularly in the thiophosphates. Replacement of the non-esterified oxygen atom in the phosphate with sulphur makes NMR shielding of the phosphorus atom qualitatively different as compared to the NMR shielding of the phosphorus atom in phosphate, H3PO4 and PH3.

Design, synthesis and biological activities of new brassinosteroid analogues with a phenyl group in the side chain.

We have prepared and studied a series of new brassinosteroid derivatives with a p-substituted phenyl group in the side chain. To obtain the best comparison between molecular docking and biological activities both types of brassinosteroids were synthesized; 6-ketones, 10 examples, and B-lactones, 8 examples. The phenyl group was introduced into the steroid skeleton by Horner-Wadsworth-Emmons. The docking studies were carried out using AutoDock Vina 1.05. Plant biological activities were established using different brassinosteroid bioassays in comparison with natural brassinosteroids. Differences in the production of the plant hormone ethylene were also observed in etiolated pea seedlings after treatment with new brassinosteroids. The most active compounds were lactone 8f and 6-oxo derivatives 8c and 9c, their biological activities were comparable or even better than naturally occurring brassinolide. Finally the cytotoxicity of the new derivatives was studied using human normal and cancer cell lines.

Synthetic study on cystinyl peptides using solution and solid phase methodology: human IgG1 hinge region.

Synthetic study on cystinyl peptides using solution and solid phase methodology was carried out with the central hinge region of immunoglobulin IgG1. In the solid phase synthesis of hexadecapeptide 1c, the time necessary for the formation of disulfide bonds between linear precursors was shortened four times by the action of pure oxygen in buffered solution, in comparison with air oxidation. The product was thus obtained devoid of impurities from side reactions. In the preparation of the shortened bis-cystinyl analogs 2k and 3d of the natural hexadecapeptide 1c, both the classical and polyethylene glycol (PEG6000) solution methods were utilized using a disulfide synthon (Boc-Cys-OPfp)2 to obtain peptide chains in a natural parallel alignment. In the PEG6000 strategy, lysine as a linker on both sides of the polymer was attached to enhance the loading capacity. The leucine residue, instead of proline one, was introduced to the carboxy terminus to facilitate a specific enzymatic cleavage of the peptides from PEG6000 by thermolysine.

Synthesis of N-succinyl-L,L-diaminopimelic acid mimetics via selective protection.

The search for potential inhibitors that target so far unexplored bacterial enzyme mono-N-succinyl-L,L-diaminopimelic acid desuccinylase (DapE) has stimulated a development of methodology for quick and efficient preparation of mono-N-acylated 2,6-diaminopimelic acid (DAP) derivatives bearing the different carboxyl groups or lipophilic moieties on their amino group.

Inhibitors of N(alpha)-acetyl-L-ornithine deacetylase: synthesis, characterization and analysis of their inhibitory potency.

A series of N (alpha)-acyl (alkyl)- and N (alpha)-alkoxycarbonyl-derivatives of L- and D-ornithine were prepared, characterized, and analyzed for their potency toward the bacterial enzyme N (alpha)-acetyl-L-ornithine deacetylase (ArgE). ArgE catalyzes the conversion of N (alpha)-acetyl-L-ornithine to L-ornithine in the fifth step of the biosynthetic pathway for arginine, a necessary step for bacterial growth. Most of the compounds tested provided IC(50) values in the muM range toward ArgE, indicating that they are moderately strong inhibitors. N (alpha)-chloroacetyl-L-ornithine (1g) was the best inhibitor tested toward ArgE providing an IC(50) value of 85 microM while N (alpha)-trifluoroacetyl-L-ornithine (1f), N (alpha)-ethoxycarbonyl-L-ornithine (2b), and N (alpha)-acetyl-D-ornithine (1a) weakly inhibited ArgE activity providing IC(50) values between 200 and 410 microM. Weak inhibitory potency toward Bacillus subtilis-168 for N (alpha)-acetyl-D-ornithine (1a) and N (alpha)-fluoro- (1f), N (alpha)-chloro- (1g), N (alpha)-dichloro- (1h), and N (alpha)-trichloroacetyl-ornithine (1i) was also observed. These data correlate well with the IC(50) values determined for ArgE, suggesting that these compounds might be capable of getting across the cell membrane and that ArgE is likely the bacterial enzymatic target.

Synthesis and utilization of 13C and 15N backbone-labeled proline: NMR study of synthesized oxytocin with backbone-labeled C-terminal tripeptide amide.

The 13C and 15N backbone-labeled proline was prepared using Oppolzer's method based on application of a sultam as chiral auxiliary. This isotopomer was used in the synthesis of the 13C, 15N backbone-labeled C-terminal tripeptide amide fragment of neurohypophyseal hormone oxytocin. Finally, this tripeptide amide was coupled by segment condensation with N-Boc- or N-Fmoc-tocinoic acid, followed by N-deprotection with TFA or piperidine. The labeled oxytocin exhibited biological activity identical with that of natural oxytocin. A detailed 1H, 13C and 15N NMR study confirmed the assigned oxytocin conformation containing a beta-turn in the cyclic part of the molecule, stabilized by H-bond(s) that can be perturbed by the C-terminal tripeptide amide moiety as indicated by comparison of NMR data for both the tocine ring in oxytocin and tocinoic acid.

O-Phosphonatomethylcholine, its analogues, alkyl esters, and their biological activity.

O-Phosphonatomethylcholine, an isopolar phosphocholine analogue with a phosphonomethyl ether group replacing a phosphomonoester residue, was prepared by reaction of diisopropyl 2-chloroethoxymethylphosphonate with dimethylamine followed by quaternization of the thus-obtained diisopropyl 2-dimethylaminoethoxymethylphosphonate with iodomethane; the ester groups in the quaternary intermediate were cleaved with bromotrimethylsilane. Replacement of dimethylamine in the reaction sequence by morpholine and/or pyrrolidine gave the N-methylmorpholinium or N-methylpyrrolidinium analogues of O-phosphonatomethylcholine. Reaction of O-phosphonomethylcholine monotetrabutylammonium salt with 1-bromoalkanes in acetonitrile afforded a series of the corresponding monoalkyl (C10-C16) esters. None of these compounds except for the hexadecyl ester exhibited any appreciable cytostatic activity against DU-145, H460, HT-29, or MES-SA cell lines in vitro (evaluated by 3H-Thd incorporation assay). The hexadecyl ester exhibited modest in vitro cytotoxic activity comparable to that of the anticancer drug miltefosine (hexadecyl O-phosphocholine). In vivo evaluation of hexadecyl O-phosphonomethylcholine [transplanted SD lymphoma in inbred SD/cub rats, 10 mg kg(-1) day(-1) intratumoral injection for 10 days] resulted in a 40% decrease in lymphoma mass.

Synthesis of S-linked glucosaminyl-4-thiohex-2-enopyranosides via allylic SN2' substitution of a tosylhexenose.

Treatment of 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-1-thio-beta-D-glucopyranose with 1,6-anhydro-3,4-dideoxy-2-O-p-toluenesulfonyl-beta-D-erythro-hex-3-enopyranose gave 2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl-(1-->4)-1,6-anhydro-2,3-dideoxy-4-thio-beta-D-erythro-hex-2-enopyranose in 86% yield. Its 1,6-anhydride bond was cleaved with methanol to give a mixture of methyl glycosides (alpha/beta approximately 5:1), from which the alpha anomer was separated by crystallization and converted into its 6-acetate, 6-methanesulfonate, or deacetylated to obtain the corresponding free methyl thiodisaccharide. The structure of the new compounds was confirmed by 1H and 13C NMR spectra.

General approach to the synthesis of persubstituted hydrophilic and amphiphilic beta-cyclodextrin derivatives.

Heptakis(2,3,6-tri-O-allyl)-beta-cyclodextrin 2 was converted to heptakis[2,3,6-tri-O-(2,3-dihydroxypropyl)]-beta-cyclodextrin 3 by osmium tetroxide-catalyzed dihydroxylation. A diastereomeric mixture of 3 was treated with sodium periodate followed by sodium borohydride to give heptakis[2,3,6-tri-O-(2-hydroxyethyl)]-beta-cyclodextrin 5 in 86% yield. Compound 5 could be quantitatively transformed into heptakis(2,3,6-tri-O-carboxymethyl)-beta-cyclodextrin 6 by TEMPO-mediated oxidation. The same reaction sequence was also applied to heptakis(2,6-di-O-allyl-3-O-methyl)-beta-cyclodextrin 8, heptakis(2,3-di-O-allyl-6-O-methyl)-beta-cyclodextrin 12, and heptakis(2,3-di-O-allyl-6-O-butyl)-beta-cyclodextrin 16; the analogous corresponding hydroxyethyl and carboxymethyl derivatives were isolated in high yields. All products were proved to be chemically uniform.

Synthesis and effect of shortened oostatic decapeptide (TMOF) analogs with isosteric structures on reproduction of Neobellieria bullata.

Oligopeptides 2a-2d derived from the oostatic decapeptide (TMOF) sequence, H-Tyr-Asp-Pro-Ala-Pro-Pro-Pro-Pro-Pro-Pro-OH (1a) and containing isosteric structures were synthesized and assayed to determine their effect during reproduction in the flesh fly Neobellieria bullata. The N-terminal linear tetra- and pentapeptides 2a, 2b containing the Pro-psi[CH2O]Ala isosteric linkage affect egg development in 80-90% of ovarioles resulting in some resorbed egg chambers, abnormal yolk deposition, the formation of large eggs with irregular yolk granules and proliferation of follicular epithelium. In comparison with their nonisosteric precursors 1b, 1c they exhibit even more accelerated oostatic activity. However, peptides 2c, 2d containing a Pro-psi[CH2S]Ala isosteric linkage are less active.

Conformational model for the consensus V3 loop of the envelope protein gp120 of HIV-1 in a 20% trifluoroethanol/water solution.

Based on experimental NMR data, a model was generated for the conformation of the disulfide-bond-closed cyclic peptide corresponding to the whole V3 loop of the consensus HIV-1 strain in a 20% trifluoroethanol/water solution. The obtained family of structures shows a prominent and well-defined amphipathic alpha helix at the C-terminal end of the peptide from Thr23 to Gln32. A series of turns characterizes the central Gly15-Tyr21 region, while the N-terminal region is poorly defined. Independent experimental data confirms the features of this model, and suggests that this type of conformation can be readily adopted when the V3 loop is in contact with a membrane. The examined V3 loop belongs to a macrophage tropic strain, and using the model, a structural explanation is proposed for the different requirements of V3 loops belonging to macrophage and T-cell line tropic HIV-1 strains.

Cyclic analogs of insect oostatic peptides: synthesis, biological activity, and NMR study.

Cyclic peptides 2a-2c, derived from the sequence of the C-terminal shortened analogs of the oostatic decapeptide H-Tyr-Asp-Pro-Ala-Pro-Pro-Pro-Pro-Pro-Pro-OH (1a), were synthesized and assayed on their effect in a reproduction of the flesh fly Neobellieria bullata. The cyclization of the N-terminal linear tetra- and pentapeptides 1b and 1c to the cyclotetra- and cyclopentapeptides 2b and 2c decreased the oostatic activity by one order of magnitude. The cyclodecapeptide 2a, which emerged spontaneously during the pentapeptide cyclization, was quite inactive. Comparative 1H and 13C NMR study on a conformation of the cyclopeptides 2a-2c, and their linear precursors 1b and 1c revealed that a space structure of the cyclic analogues 2b and 2c is too restricted to adopt a biological conformation necessary for receptor binding and therefore only minor oostatic activity is observed after their application. The lack of the oostatic activity in the case of the more flexible dimeric analogue 2a is ascribed to the size of its molecule and its overall shape that is not compatible with a receptor binding.

[Nonpolar components of the leaves of Philadelphus coronarius L]. / Nepolárne obsahové látky listov Philadelphus coronarius L.

The paper deals with the isolation of constituents from light petrol and chloroform extracts of the leaves of Philadelphus coronarius L., Saxifragaceae. From the light petrol extract uvaol and 3 beta,28-dihydroxyoleanane-11(12),13(18)-diene were isolated, while coumarins (umbelliferone, scopolin), stigmasteryl-3 beta-D-glucoside and the alcane type carbohydrate-C29H60 were isolated from the chloroform extract. The isolated compounds were identified by spectroscopic means and by comparison with standards and the literature data.

[Monodesmosidic saponins in Cynara cardunculus L]. / Monodezmozidové saponíny z Cynara cardunculus L.

From an ethanolic extract of the flower buds of Cynara cardunculus L. (Asteraceae), two monodesmosidic saponins, cynarasaponin B and a new cynarasaponin K, were isolated. The isolated compounds were identified by spectroscopic means and by comparison with standards and the literature data.

[Constituents of the leaves of Holodiscus discolor (Pursh) Maxim]. / Obsahové látky listov Holodiscus discolor (PURSH) MAXIM.

The paper deals with the isolation of constituents from light petrol and methanol extracts of the leaves of Holodiscus discolor (PURSH) MAXIM., Rosaceae. beta-sitosterol and taraxasterol were isolated from the light petrol extract, luteolin-7-O-glucoside was isolated from the methanol extract. The isolated compounds were identified by spectroscopic means and by comparison with authentic samples.

Efficient synthesis of 2'-deoxynucleoside 3'-C-phosphonates: reactivity of geminal hydroxyphosphonate moiety.

In this report we present a novel, simple way for the synthesis of 3'-C-phosphonate derivatives of all four basic 2'-deoxynucleosides in both fully protected and deprotected forms. The reactivity of the geminal hydroxy phosphonate moiety located at the 3'-carbon atom of the nucleoside was studied with respect to the use of this type of nucleoside phosphonic acid for the preparation of short oligonucleotides, namely, dinucleoside monophosphate analogues.

[Sterols in Lilium candidum L]. / Steroly v Lilium candidum L.

From the butanolic extract of petals of Lilium candidum L., beta-sitosterol and beta-sitosterol glucoside were isolated. The isolated compounds were identified by spectroscopic means and by comparison with literature data; beta-sitosterol glucoside was isolated in genus Lilium L. for the first time.

Synthesis, analgesic activity, and binding properties of some epibatidine analogs with a tropine skeleton.

A series of epibatidine analogs and their positional isomers bearing an 8-azabicyclo[3.2.1]octane moiety is described. Also some of their simplified analogs bearing a 3-piperidine moiety are reported. Their receptor binding profiles (5-HT1A, 5-HT1B, M1, M2, neuronal nicotinic receptor) and analgesic activity (hot plate, acetic acid induced writhing) have been studied. Some of the compounds, especially those containing an 8-azabicyclo[3.2.1]oct-2-ene moiety possess high afinity for the nicotinic cholinergic receptor. The most analgesically active compounds are also highly toxic. Optimized structures (PM3-MOPAC, Alchemy 2000, Tripos Inc.) of compounds 1-9 were compared with that of epibatidine.

A new steroidal alkaloid from the roots of Cynanchum caudatum.

A new steroidal alkaloid, 12-O-nicotinoylsarcostin, gagamine (1), was isolated from the roots of Cynanchum caudatum Max. (Asclepiadaceae), together with a known alkaloid, gagaminine (2). Their structures were established using spectroscopic methods, some 13C-NMR data of 2 have to be revised.