Synthesis of a burkholdine analogue containing β-hydroxytyrosine

Synthesis of a β-OHTyr-containing Bk analogue, a cyclic octalipopeptide with antifungal activities, is described. Since β-OHTyr-containing peptides generally are unstable in strong acidic conditions, synthesis of β-HOTyr-containing peptides by SPPS have rarely been reported. To overcome this problem, we found that using distilled TFA removed the protecting groups of side chains of β-OHTyr-containing Bk analogue, which was prepared by Fmoc-SPPS.

Abbreviations: β-OHTyr: β-hydroxytyrosine; β-OHAsn: β-hydroxyasparagine; Bk: burkholdine; FAA: fatty acyl amino acid; β-MeOTyr: β-methoxytyrosine; SPPS: solid phase peptide synthesis; MIC: minimun inhibitory concentration; DMF: dimethyl formamide; DIPEA: diisopropylethylamine; DIPC: diisopropylcarbodiimide; HOBt: 1-hydroxybenzotriazole; Fmoc: 9-fluorenylmethyloxycarbonyl; HFIP: 1,1,1,3,3,3-hexafluoropropan-2-ol; TFA: trifluoroacetic acid; LAP: N-lauryl ?3-amino-4-carbamolypropanoic acid; HPLC: high performance liquid chromatography; ESI-TOFMS: electrospray ionization-time of flight mass spectrometry; Bn: benzyl; Boc: t-butyloxycatbonyl; 2-CTC: 2-chlorotritylchloride.     

Synthesis and antidiabetic performance of β-amino ketone containing nabumetone moiety

We wish to report the further design and improved synthesis that resulted in two series of target molecules, TM-1 and TM-2, with remarkably simplified structures containing β-amino ketone of discrete nabumetone moiety. These were obtained via a 'one-pot, two-step, three-component' protocol of Mannich reaction with yield up to 97%. A total of 28 out of 31 new compounds were characterized using (1)H NMR, (13)C NMR, ESI MS and HRMS techniques. Studies on their antidiabetic activities, screened in vitro at 10 μg mL(-1) level, indicate that TM-2 possesses peroxisome proliferator-activated receptor activation and α-glucosidase inhibition activity significantly stronger than that of TM-1, and also that of the series B compounds that were previously synthesized by the group. Analysis of the structure-activity relationship points to the sulfanilamide unit as the most probable potent group of β-amino ketone and, on the basis of which, a tangible strategy is presented for the development of new antidiabetic drugs.     

Synthesis of cyclic RGD-peptides containing β-amino acids

Summary The solid phase synthesis of cyclic RGD-peptides containing β-amino acids according to two different protocols is described. The second strategy allows multiple or combinatorial syntheses of this type of cyclic peptides, because it enables backbone cyclization while the RGD-peptide is still bound to the resin. The newly synthesized RGD-peptides were characterized by MALDI-TOF MS and NMR and their physiological activity was determined by aggregometry.     

Cephalosporinase and penicillinase activities of a β-lactamase from Pseudomonas pyocyanea

1. Pseudomonas pyocyanea N.C.T.C. 8203 produces a beta-lactamase that is inducible by high concentrations of benzylpenicillin or cephalosporin C. Methicillin appeared to be a relatively poor inducer, but this could be attributed in part to its ability to mask the enzyme produced. Much of the enzyme is normally cell-bound. 2. No evidence was obtained that the crude enzyme preparation consisted of more than one beta-lactamase and the preparation appeared to contain no significant amount of benzylpenicillin amidase or of an acetyl esterase. 3. The maximum rate of hydrolysis of cephalosporin C and several other derivatives of 7-aminocephalosporanic acid by the crude enzyme was more than five times that of benzylpenicillin. Methicillin, cloxacillin, 6-aminopenicillanic acid and 7-aminocephalosporanic acid were resistant to hydrolysis, and methicillin and cloxacillin were powerful competitive inhibitors of the action of the enzyme on easily hydrolysable substrates. 4. Cephalosporin C, cephalothin and cephaloridine yielded 2 equiv. of acid/mole on enzymic hydrolysis, and deacetylcephalorsporin C yielded 1 equiv./mole. Evidence was obtained that the opening of the beta-lactam ring of cephalosporin C and cephalothin is accompanied by the spontaneous expulsion of an acetoxy group and that of cephaloridine by the expulsion of pyridine. 5. A marked decrease in the minimum inhibitory concentration of benzylpenicillin and several hydrolysable derivatives of 7-aminocephalosporanic acid was observed when the size of the inoculum was decreased. This suggested that the production of a beta-lactamase contributed to the factors responsible for the very high resistance of Ps. pyocyanea to these substances. It was therefore concluded that the latter might show synergism with the enzyme inhibitors, methicillin and cloxacillin, against this organism.     

Production of cellulase and β-glucosidase activities following growth of Streptomyces hygroscopicus on cellulose containing media

The actinomycete, Streptomyces hygroscopicus was shown to be capable of producing extracellular cellulase and cell associated -glucosidase activity during growth on cellulose containing media. Cell homogenates were shown to contain a -glucosidase fraction which was stable for up to 24h. at 30°C and had half-lives of 480min. and 220min. at 40 and 50°C, respectively. The enzyme fraction was also shown to be optimally active at pH 4.0 suggesting that it might represent a suitable supplement for fungal cellulase systems, deficient in -glucosidase activity.     

Evaluation of dimerization–inhibitory activities of cyclic peptides containing a β-hairpin loop sequence of the EGF receptor

Structure–activity relationships of cyclic peptides mimicking the β-hairpin structure of the ‘dimerization arm’ at residues 242–259 of the EGF receptor are examined. Cyclic peptides containing the arm head of the β-hairpin loop showed inhibitory activity toward the EGF receptor’s dimerization. Cyclic peptides containing a Retro-Inverso sequence of the dimerization arm showed clear inhibitory effects on the dimerization in vitro and efficiently suppressed the proliferation of A431 cells, which abundantly express the EGF receptor on their surface. The effects at a specific hydrophobic site of the loop structure were expected to enhance the interactions with the receptor.     

Synthesis and anti-TMV activity of novel β-amino acid ester derivatives containing quinazoline and benzothiazole moieties

Here, a series of β-amino acid ester derivatives containing quinazoline and benzothiazoles was synthesized and evaluated for anti-tobacco mosaic virus (TMV) activity. The compounds 3n, 3o, 3p and 3q showed good antiviral activity against TMV at a concentration of 500 μg/mL, with curative rates of 55.55%, 52.32%, 52.77% and 50.91%, respectively, and protection rates of 52.33%, 55.96%, 54.21% and 50.98%, respectively. These values were close to those of the commercially available antiviral agent ningnanmycin (which has curative and protection rates of 55.27% and 52.16%, respectively). To our knowledge, this is the first report of the anti-TMV activity of β-amino acid ester derivatives containing quinazoline and benzothiazoles moieties; the results indicate that these novel compounds can potentially be used as protective agents against TMV diseases.     

Synthesis and moisture absorption and retention activities of a carboxymethyl and a quaternary ammonium derivative of α,α-trehalose

Carboxymethyl α,α-trehalose (CMT) and a quaternary ammonium derivative of α,α-trehalose (QT) were successfully prepared, and their moisture absorption and retention activities were assessed. Results showed that both CMT and QT had better moisture absorption abilities at 43% and 81% relative humidity (RH) than α,α-trehalose. In addition, the two α,α-trehalose derivatives had better moisture retention abilities than α,α-trehalose under three humidity conditions: 81% RH, 43% RH, and under dry conditions. Therefore, carboxymethylation and quaternarization could improve the moisture absorption and retention abilities of α,α-trehalose. CMT and QT showed better moisture absorption ability and moisture retention ability than that of hyaluronan (HA), and could potentially find a use as moisture retention ingredient, for example, in cosmetics.     

Characterization of a β-glucosidase from Sulfolobus solfataricus for isoflavone glycosides

The specific activity of a recombinant β-glucosidase from Sulfolobus solfataricus for isoflavones was: daidzin > glycitin > genistin > malonyl genistin > malonyl daidzin > malonyl glycitin. The hydrolytic activity of this enzyme for daidzin was highest at pH 5.5 and 90°C with a half-life of 18 h, a K _m of 0.5 mM, and a k _cat of 2532 s⁻¹. The enzyme converted 1 mM daidzin to 1 mM daidzein after 1 h with a molar yield of 100% and a productivity of 1 mM h⁻¹. Among β-glucosidases, that from S. solfataricus β had the highest thermostability, k _cat, k _cat/K _m, conversion yield, and productivity in the hydrolysis of daidzin.     

Synthesis and evaluation of the anti-proliferative and NF-κB activities of a library of simplified tylophorine analogs

Tylophorine and many related phenanthropiperidine alkaloids are extraordinarily potent anti-proliferative agents. Despite their impressive anti-cancer activity, clinical development of these alkaloids has been hampered by their poor solubility and neurological side effects. Although it has been suggested that developing polar phenanthropiperidines will mitigate these undesired properties, the lack of practical methods for the synthesis of such analogues has limited this effort. Here, we present a concise synthetic approach to N-substituted phenanthropiperidines, which enabled a systematic investigation of structure-activity relationships at an underexplored region of the tylophorine scaffold. This work suggests that ring E of tylophorine is essential for the anti-proliferative activity of the 6,7,10,11-tetramethoxy-1,2,3,4-tetrahydrodibenzo[f,h]isoquinoline core scaffold.     

Synthesis and 121Sb mössbauer study of a number of organoantimony(III) compounds containing antimony-main group V element bonds

The synthesis of organoantimony(III) compounds of the type R₂SbMR′₂ in which R,R′=Et or Ph and M=N, P or As has been investigated. Diphenylaminodiethylstibine and diphenylaminodiphenylstibine were successfully synthesized. Attempts to prepare phosphinostibines and arsinostibines of the type R₂SbMR′₂ (M=P, As) failed and resulted in the formation of the corresponding diphosphines, diarsines, and distibines Only in the case of the synthesis of Ph₂AsSbPh₂ was an analytically pure product obtained. A series of antimony(III) compounds containing antimony-main group V element bonds has been investigated by ¹²¹Sb Mössbauer spectroscopy. The near consistency in the isomer shift (−4.0 to −4.6 mm/s relative to InSb) implies almost no change in the s-character in the total antimony-ligand bonds. Variation in the values of the quadrupole coupling constant and the asymmetry factor are discussed in terms of structure and/or changes in the p-character of the antimony-ligand bonds.     

Synthesis of cholestane glycosides bearing OSW-1 disaccharide or its 1→4-linked analogue and their antitumor activities

For further structure–activity relationship (SAR) research of OSW saponins, a cholestane glycoside, namely 3β, 16β, 26-trihydroxycholest-5-en-22-one 16-O-(2-O-4-methoxybenzoyl-β-d-xylopyranosyl)-(1→3)-2-O-acetyl-α-l-arabinopyranoside (1) together with two 1→4-linked disaccharide analogues (2 and 3) were synthesized. Their cytotoxic activities were evaluated by the standard MTT assay. Compound 1 showed potent cytotoxicity against five types of human tumor cells, with IC₅₀ ranging between 1.3 and 73 nM.     

Synthesis and characterization of quaternized β-chitin

Water-soluble 2′-O-hydroxypropyltrimethylammoniumchitin chloride (2′-O-HTACCt) was prepared directly from β-chitin and 3-chloro-2-hydroxypropyltrimethylammonium chloride (CTA) in basic medium. The effect of alkali concentration, reaction temperature, reaction time, and dosage of CTA on yield and degree of substitution (DS) of 2′-O-HTACCt were studied. These quaternized chitin derivatives were characterized by FTIR and ¹H NMR spectroscopy, conductometric titration, and elemental analysis methods. Research results indicate that β-chitin can react directly with CTA to produce a water-soluble 2′-O-HTACCt derivative with a high DS. The optimal preparation conditions were determined to be 35-40 wt % (aq NaOH), 40 °C (reaction temperature), 6 h (reaction time), and 4 (molar ratio of CTA to β-chitin unit).     

Synthesis and characterization of a cell-permeable bimodal contrast agent targeting β-galactosidase

Noninvasive monitoring of intracellular targets such as enzymes, receptors, or mRNA by means of magnetic resonance imaging (MRI) is increasingly gaining relevance in various research areas. A vital prerequisite for their visualization is the development of cell-permeable imaging probes, which can specifically interact with the target that characterizes the cellular or molecular process of interest. Here, we describe a dual-labeled probe, Gd-DOTA-k(FR)-Gal-CPP, designed to report the presence of intracellular β-galactosidase (β-gal) enzyme by MRI. This conjugate consists of a galactose based core serving as cleavable spacer, incorporated between the cell-penetrating peptide D-Tat(49-57) and reporter moieties (Gd-DOTA, fluorescein (FR)). We employed a facile building block approach to obtain our bimodal probe, Gd-DOTA-k(FR)-Gal-CPP. This strategy involved the preparation of the building blocks and their subsequent assembly using Fmoc-mediated solid phase synthesis, followed by the complexation of ligand 14 with GdCl(3). Gd-DOTA-k(FR)-Gal-CPP showed a considerably higher relaxivity enhancement (16.8±0.6 mM(-1)s(-1), 123 MHz, ～21°C) relative to the commercial Gd-DOTA (4.0±0.12 mM(-1)s(-1), 123MHz, ～21 °C). The activation of Gd-DOTA-k(FR)-Gal-CPP was based on a cellular retention strategy that required enzymatic cleavage of the delivery vector from galactose moiety following the cell internalization to achieve a prolonged accumulation of the reporter components (Gd-DOTA/FR) in the β-gal expressing cells. Cellular uptake of Gd-DOTA-k(FR)-Gal-CPP in β-gal expressing C6/LacZ and enzyme deficient parental C6 rat glioma cells was confirmed by fluorescence spectroscopy, MR imaging and ICP-AES measurements. All methods showed higher accumulation of measured reporters in C6/LacZ cells compared to enzyme deficient parental C6 cells. Fluorescence microscopy of cells labeled with Gd-DOTA-k(FR)-Gal-CPP indicated a predominantly vesicular localization of the green fluorescent conjugate around cell nuclei. This cellular distribution was most likely responsible for the observed non-specific background signal in the enzyme deficient C6 cells. Even though the specific accumulation of our bimodal probe has to be further improved, it could be already used for cell imaging by MRI and optical modalities.     

Synthesis of methyl α- and β-maltotriosides and aryl β-maltotriosides

Reaction of β-maltotriose hendecaacetate with phosphorus pentachloride gave 2′,2″,3,3′,3″,4″,6,6′,6″,-nona-O-acetyl-(2)-O-trichloroacetyl-β-maltotriosyl chloride (2) which was isomerized into the corresponding α anomer (8). Selective ammonolysis of 2 and 8 afforded the 2-hydroxy derivatives 3 and 9, respectively; 3 was isomerized into the α anomer 9. Methanolysis of 2 and 3 in the presence of pyridine and silver nitrate and subsequent deacetylation gave methyl α-maltotrioside. Likewise, methanolysis and O-deacetylation of 9 gave methyl β-maltotrioside which was identical with the compound prepared by the Koenigs—Knorr reaction of 2,2′,2″,3,3′,3″,4″,6,6′,6″-deca-O-acetyl-α-maltotriosyl bromide (12) with methanol followed by O-deacetylation. Several substituted phenyl β-glycosides of maltotriose were also obtained by condensation of phenols with 12 in an alkaline medium. Alkaline degradation of the o-chlorophenyl β-glycoside decaacetate readily gave a high yield of 1,6-anhydro-β-maltotriose.     

Synthesis and evaluation of novel phenoxypropanolamine derivatives containing acetanilides as potent and selective β3-adrenergic receptor agonists

In the search for potent and selective human β3-adrenergic receptor (AR) agonists as potential drugs for the treatment of obesity and noninsulin-dependent (type II) diabetes, a novel series of phenoxypropanolamine derivatives containing acetanilides were prepared and their biological activities were evaluated at the human β3-, β2-, and β1-ARs. Several of the analogues (21a, 21b, and 27a) exhibited potent agonistic activity at the β3-AR. Among the compounds described herein, the N-methyl-1-benzylimidazol-2-ylacetanilide derivative (21b) was found to be the most potent and selective β3-AR agonist, with an EC₅₀ value of 0.28 μM and no agonistic activity for either the β1- or β2-AR. In addition, 21b showed significant hypoglycemic activity in a rodent diabetic model.     

Synthesis and changes in affinity for NOP and opioid receptors of novel hexapeptides containing β2-tryptophan analogues

We report the synthesis and the biological activity of new analogues of Ac-RFMWMK-NH₂ and Ac-RYYRWK-NH₂, modified in position 4 and 5, respectively, with incorporation of newly synthesized β²-tryptophan analogues. Trp was substituted by the (S)-2-(1-methyl-1H-indol-3-yl)propionic residue or by (S)-2-(5-methoxy-1H-indol-3-yl)propionic residue. The biological activity (pEC₅₀ and E_max) of these compounds was tested on electrically stimulated preparations of rat vas deferens. The 5-methoxy β-tryptophan group reverses the affinity of the compounds.     

Physiological activities of a β-glucan produced by Panebacillus polymyxa

In vitro bioactivities of a beta-glucan produced by Panebacillus polymyxa JB115 were investigated. Nitric oxide production by RAW 264.7 macrophage cells pre-treated with beta-glucan JB115 (from 0.1 to 1 mg ml(-1)) was significantly increased, compared to that in untreated cells (P < 0.001). The beta-glucan JB115 increased superoxide radical-scavenging activity by 66% at 1 mg ml(-1). It also suppressed hyaluronidase (32%) and collagenase (33%) activities and, additionally, displayed antitumor activity, blocking the growth of Sarcoma 180 cells in a concentration-dependent manner. The immune-stimulatory, antioxidant, collagenase inhibitory and hyaluronidase inhibitory effects of the beta-glucan support its potential role in the prevention of bacterial disease against fish and in the protection of skin against aging.     

Synthesis and SAR of novel benzoxaboroles as a new class of β-lactamase inhibitors

A new class of benzoxaborole β-lactamase inhibitors were designed and synthesized. 6-Aryloxy benzoxaborole 22 inhibited AmpC P99 and CMY-2 with K_i values in the low nanomolar range. Compound 22 restored antibacterial activity of ceftazidime against Enterobacter cloacae P99 expressing AmpC, a class C β-lactamase enzyme. The SAR around the arylbenzoxaboroles, which included the influence of linker and substitutions was also established.