Human ß-Defensin 1 and ß-Defensin 3 (Mouse Ortholog mBD14) Function as Full Endogenous Agonists at Select Melanocortin Receptors.

ß-Defensin 3 (BD3) was identified as a ligand for the melanocortin receptors (MCRs) in 2007, although the pharmacology activity of BD3 has not been clearly elucidated. Herein, it is demonstrated that human BD3 and mouse BD3 are full micromolar agonists at the MCRs. Furthermore, mouse ß-defensin 1 (BD1) and human BD1 are also MCR micromolar agonists. This work identifies BD1 as an endogenous MCR ligand and clarifies the controversial role of BD3 as a micromolar agonist.

1,2,3-Triazole Rings as a Disulfide Bond Mimetic in Chimeric AGRP-Melanocortin Peptides: Design, Synthesis, and Functional Characterization.

The melanocortin system is involved in the regulation of complex physiological functions, including energy and weight homeostasis, feeding behavior, inflammation, sexual function, pigmentation, and exocrine gland function. The five melanocortin receptors that belong to the superfamily of G protein-coupled receptors (GPCRs) are regulated by endogenously expressed agonists and antagonists. The aim of this study was to explore the potential of replacing the disulfide bridge in chimeric AGRP-melanocortin peptide Tyr-c[Cys-His-d-Phe-Arg-Trp-Asn-Ala-Phe-Cys]-Tyr-NH2 (1) with 1,2,3-triazole moieties. A series of 1,2,3-triazole-bridged peptidomimetics were designed, synthesized, and pharmacologically evaluated at the mouse melanocortin receptors. The ligands possessed nanomolar to micromolar agonist cAMP signaling potency. A key finding was that the disulfide bond in peptide 1 can be replaced with the monotriazole ring with minimal effect on the functional activity at the melanocortin receptors. The 1,5-disubstituted triazole-bridged peptide 6 showed equipotent functional activity at the mMC3R and modest 5-fold decreased agonist potency at the mMC4R compared to those of 1. Interestingly, the 1,4- and 1,5-disubstituted isomers of the triazole ring resulted in different selectivities at the receptor subtypes, indicating subtle structural features that may be exploited in the generation of selective melanocortin ligands. Introducing cyclic and acyclic bis-triazole moieties into chimeric AGRP template 1 generally decreased agonist activity. These results will be useful for the further design of neuronal chemical probes for the melanocortin receptors as well as in other receptor systems.

Microwave-assisted solid-phase synthesis of side-chain to side-chain lactam-bridge cyclic peptides.

Side-chain to side-chain lactam-bridged cyclic peptides have been utilized as therapeutic agents and biochemical tools. Previous synthetic methods of these peptides need special reaction conditions, form side products and take longer reaction times. Herein, an efficient microwave-assisted synthesis of side-chain to side-chain lactam-bridge cyclic peptides SHU9119 and MTII is reported. The synthesis time and efforts are significantly reduced in the present method, without side product formation. The analytical and pharmacological data of the synthesized cyclic peptides are in accordance with the commercially obtained compounds. This new method could be used to synthesize other side-chain to side-chain lactam-bridge peptides and amenable to automation and extensive SAR compound derivatization.

Synthesis and Pharmacology of α/ß(3)-Peptides Based on the Melanocortin Agonist Ac-His-dPhe-Arg-Trp-NH2 Sequence.

The melanocortin-3 and -4 receptors are expressed in the brain and play key roles in regulating feeding behavior, metabolism, and energy homeostasis. In the present study, incorporation of ß(3)-amino acids into a melanocortin tetrapeptide template was investigated. Four linear α/ß(3)-hybrid tetrapeptides were designed with the modifications at the Phe, Arg, and Trp residues in the agonist sequence Ac-His-dPhe-Arg-Trp-NH2. The most potent mouse melanocortin-4 receptor (mMC4R) agonist, Ac-His-dPhe-Arg-ß(3)hTrp-NH2 (8) showed 35-fold selectivity versus the mMC3R. The study presented here has identified a new template with heterogeneous backbone for designing potent and selective melanocortin receptor ligands.

Computer-assisted rational design, synthesis, and bioassay of non-steroidal anti-inflammatory agents.

A focused dataset of previously synthesized and tested [1,2,4]-triazolo[1,5-a]pyridines and pyridine-3-carboxylates was studied by Molecular Field Topology Analysis (MFTA) to identify steric and electronic determinants of anti-inflammatory activity useful for the design and synthesis of new anti-inflammatory agents. Rational design based on the MFTA model identified eleven novel pyridine-3-carboxylates (2a-e and 3a-f) as promising. After synthesis and screening, three of (2a, 2c, 3a) revealed potent anti-inflammatory activity exceeding that of indomethacin, the reference inhibitor for artificially induced edema in rats.

Cysteinoyl- and cysteine-containing dipeptidoylbenzotriazoles with free sulfhydryl groups: easy access to N-terminal and internal cysteine peptides.

N-Protected cysteines 4a-c each with a free sulfhydryl group were prepared in 70-75% yields by treatment of L-cysteine with 1-(benzyloxycarbonyl) benzotriazole (Cbz-Bt) 1a, N-(tert-butyloxy-carbonyl)benzotriazole (Boc-Bt) 1b, and 1-(9-fluorenylmethoxy-carbonyl)benzotriazole (Fmoc-Bt) 1c, respectively. N-Protected, free sulfhydryl cysteines 4a-c were then converted into the corresponding N-protected, free sulfhydryl cysteinoylbenzotriazoles 7a-c (70-85%), which on treatment with diverse amino acids and dipeptides afforded the corresponding N-protected, free sulfhydryl N-terminal cysteine dipeptides 8a-e and tripeptides 8f-h in 73-80% yields. N-Protected, free sulfhydryl cysteine-containing dipeptides 9a,b were converted into the corresponding N-protected, free sulfhydryl dipeptidoylbenzotriazoles 10a,b (69-81%), which on treatment with amino acids, dipeptides, and a tripeptide afforded internal cysteine tripeptides 11a-c, tetrapeptides 11d,e and pentapeptide 11f, each containing a N-protected, free sulfhydryl groups in 70-90% yields under mild conditions. Treatment of N-protected, free sulfhydryl cysteinoylbenzotriazole 7a with diamines 12a,b afforded directly the cysteine-containing disulfide-bridged cyclic peptides 14a,b in 50% yields.

Design, synthesis, and biological activity of a novel series of 2,5-disubstituted furans/pyrroles as HIV-1 fusion inhibitors targeting gp41.

Based on molecular docking analysis of earlier results, we designed a series of 2,5-disubstituted furans/pyrroles (5a-h) as HIV-1 entry inhibitors. Compounds were synthesized by Suzuki-Miyaura cross coupling, followed by a Knoevenagel condensation or Wittig reaction. Four of these compounds were found to be effective in inhibiting HIV-1 infection, with the best compounds being 5f and 5h, which exhibited significant inhibition on HIV-1(IIIB) infection at micromolar levels with low cytotoxicity. These compounds are also effective in blocking HIV-1 mediated cell-cell fusion and the gp41 six-helix bundle formation, suggesting that they are also HIV-1 fusion inhibitors targeting gp41 and have potential to be developed as a new class of anti-HIV-1 agents.

Benzotriazole-mediated syntheses of depsipeptides and oligoesters.

Reactions of O-Pg(α-hydroxyacyl)benzotriazoles with (a) unprotected α-hydroxycarboxylic acids, (b) amino acids, and (c) amines afforded, respectively, chirally pure (a) oligoesters, (b) depsidipeptides, and (c) amide conjugates (yields 52-94%). N-Pg(α-Aminoacyl)benzotriazoles reacted with α-hydroxycarboxylic acids to yield depsidipeptides (47-87%). N-Pg(depsidipeptidoyl)benzotriazoles, obtained from depsidipeptides, gave depsitripeptides (yields 55-78%) on reaction with amino acids and α-hydroxycarboxylic acids. O-Acylation of α-hydroxycarboxylic acids with N-Pg(α-aminoacyl)benzotriazoles followed by deprotection produced unprotected depsides useful for the preparation of depsitripeptides.

DBU-catalyzed transprotection of N-Fmoc-cysteine di- and tripeptides into S-Fm-cysteine di- and tripeptides.

The transprotection of N-Fmoc-cysteine containing di- and tripeptides possessing a free SH group to produce the corresponding S-Fm-cysteine di- and tripeptides bearing a free amino group is accomplished efficiently with DBU in dry THF. The N-Fmoc to S-Fm transformation mechanism is discussed. S-Fm-Cysteine di- and tripeptides readily form amide bonds on coupling with N-(Pg-α-aminoacyl)benzotriazoles and N-(Pg-α-dipeptidoyl)benzotriazoles to give larger peptides.

Chemical ligation of S-scylated cysteine peptides to form native peptides via 5-, 11-, and 14-membered cyclic transition states.

Cysteine-containing dipeptides 3a-l, (3b+3b') (compound numbers in parentheses are used to indicate racemic mixtures; thus (3b+3b') is the racemate of 3b and 3b'), and tripeptide 13 were synthesized in 68-96% yields by acylation of cysteine with N-(Pg-α-aminoacyl)- and N-(Pg-α-dipeptidoyl)benzotriazoles (where Pg stands for protecting group in the nomenclature for peptides throughout the paper) in the presence of Et(3)N. Cysteine-containing peptides 3a-l and 13 were S-acylated to give S-(Pg-α-aminoacyl)dipeptides 5a-l and S-(Pg-α-aminoacyl)tripeptide 14 without racemization in 47-90% yields using N-(Pg-α-aminoacyl)benzotriazoles 2 in CH(3)CN-H(2)O (7:3) in the presence of KHCO(3). (In our peptide nomenclature, the prefixes di-, tri-, etc. refer to the number of amino acid residues in the main peptide chain; amino acid residues attached to sulfur are designated as S-acyl peptides. Thus we avoid use of the prefix "iso".) Selective S-acylations of serine peptide 3k and threonine peptide 3l containing free OH groups were thus achieved in 58% and 72% yield, respectively. S-(Pg-α-aminoacyl)cysteines 4a,b underwent native chemical ligations to form native dipeptides 3f,i via 5-membered cyclic transition states. Microwave irradiation of S-(Pg-α-aminoacyl)tripeptide 15 and S-(Pg-α-aminoacyl)tetrapeptide 17 in the presence of NaH(2)PO(4)/Na(2)HPO(4) buffer solution at pH 7.8 achieved chemical ligations, involving intramolecular migrations of acyl groups, via 11- and 14-membered cyclic transition states from the S-atom of a cysteine residue to a peptide terminal amino group to form native peptides 19 and 20 in isolated yields of 26% and 23%, respectively.

Design, synthesis, and biological activity of novel 5-((arylfuran/1H-pyrrol-2-yl)methylene)-2-thioxo-3-(3-(trifluoromethyl)phenyl)thiazolidin-4-ones as HIV-1 fusion inhibitors targeting gp41.

On the basis of our earlier molecular docking analysis, we designed and synthesized 5-((arylfuran/1H-pyrrol-2-yl)methylene)-2-thioxo-3-(3-(trifluoromethyl)phenyl)thiazolidin-4-ones (12a-o) as HIV-1 entry inhibitors. Compounds 12a-o effectively inhibited infection by both laboratory-adapted and primary HIV-1 strains and blocked HIV-1 mediated cell-cell fusion and gp41 six-helix bundle formation. Molecular docking analyses on two highly active inhibitors, 12b, containing a carboxylic acid group, and 12m, containing a tetrazole group, indicated that they both fit snugly into the hydrophobic cavity of HIV-1 gp41 from which each has important ionic interactions with lysine 574 (K574). By contrast, molecular docking of 12i, a less active compound containing a pyrrole instead of a furan ring, indicated a completely different orientation from 12b and 12m and missed critical interactions.

QSAR modeling, synthesis and bioassay of diverse leukemia RPMI-8226 cell line active agents.

A rigorous QSAR modeling procedure employing CODESSA PRO descriptors has been utilized for the prediction of more efficient anti-leukemia agents. Experimental data concerning the effect on leukemia RPMI-8226 cell line tumor growth of 34 compounds (treated at a dose of 10 µM) was related to their chemical structures by a 4-descriptor QSAR model. Four bis(oxy)bis-urea and bis(sulfanediyl)bis-urea derivatives (4a, 4b, 8, 11a) predicted as active by this model, together with 11b predicted to be of low activity, were synthesized and screened for anti-tumor activity utilizing 55 different tumor cell lines. Compounds 8 and 11a showed anti-tumor properties against most of the adopted cell lines with growth inhibition exceeding 50%. The highly promising preliminary anti-tumor properties of compounds 8 and 11a, were screened at serial dilutions (10(-4)-10(-8) µM) for determination of their GI(50) and TGI against the screened human tumor cell lines. Compound 11a (GI(50) = 1.55, TGI = 8.68 µM) is more effective than compound 8 (GI(50)=58.30, TGI = > 100 µM) against the target leukemia RPMI-8226 cell line. Compound 11a also exhibits highly pronounced anti-tumor properties against NCI-H226, NCI-H23 (non-small cell lung cancer), COLO 205 (colon cancer), SNB-75 (CNS cancer), OVCAR-3, SK-OV-3 (ovarian cancer), A498 (renal cancer) MDA-MB-231/ATCC and MDA-MB-468 (breast cancer) cell lines (GI(50) = 1.95, 1.61, 1.38, 1.56, 1.30, 1.98, 1.18, 1.85, 1.08, TGI = 8.35, 6.01, 2.67, 8.59, 4.01, 7.01, 5.62, 6.38, 5.63 µM, respectively). Thus 11a could be a suitable lead towards the design of broad spectrum anti-tumor active agents targeting various human tumor cell lines.

Regioselective synthesis and molecular modeling study of vasorelaxant active 7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones.

Nitrilimines (PhC(-):N(+):NR') generated in situ from hydrazonoyl chlorides 2a,b reacted regioselectively with 5-arylidene-2,2-dimethyl[1,3]dioxane-4,6-diones 1a-f to afford 1,3,4-triaryl-8,8-dimethyl-7,9-dioxa-1,2-diaza-spiro[4.5]dec-2-ene-6,10-diones 3a-l. In vitro vasodilation activity screening of the synthesized compounds using isolated thoracic aortic rings of male Wister rats pre-contracted with norepinephrine hydrochloride revealed considerable vasodilation activity; compounds 3f and 3j had IC(50) (concentration necessary for 50% reduction of maximal norepinephrine hydrochloride induced contracture) of 0.325, 0.321 mM, respectively. Molecular modeling, including fitting to a 3D-pharmacophore model using Discovery studio 2.1 programs and their docking into optimized alpha(1)-AR homology models as alpha(1)-AR antagonist showed high-docking score and fit values. The experimental in vitro vasodilation activity of compounds 3a-l was consistent with the molecular modeling.

The chemical ligation of selectively S-acylated cysteine peptides to form native peptides via 5-, 11- and 14-membered cyclic transition states.

Cysteine and C-terminal cysteine peptides are selectively S-acylated at 0-20 degrees C by N-(Pg-alpha-aminoacyl)benzotriazoles to give N-Pg-S-acyl-isodi-, -isotri-, and -isotetra-peptides isolated in good yields. N-Fmoc-S-acyl-isopeptides are Fmoc deprotected to afford free S-acyl-isopeptides isolated in high yields. S-Acyl-isodi-, S-acyl-isotetra-, and S-acyl-isopentapeptides undergo chemical ligation; migration of the cysteine S-acyl groups to the N-terminal amino acids via 5-, 11-, and 14-membered transition states giving the corresponding native di-, tetra-, and penta-peptides. By contrast, the Sacyl-isotripeptide prefers intermolecular acylation from one molecule to another over an 8-membered intramolecular transition state. The developed methodology allows convenient isolation of stable, unprotected S-acyl cysteine peptides including the first isolation of S-acyl-isopeptides, which should facilitate the investigation of ligation by physical organic chemistry techniques.

Efficient preparation of aminoxyacyl amides, aminoxy hybrid peptides, and alpha-aminoxy peptides.

N-(Pg-alpha-aminoxy acids) 1a-g are converted to N-(Pg-alpha-aminoxyacyl)benzotriazoles 2a-g, which react under mild conditions with amines, alpha-amino acids/alpha-dipeptides, and alpha-aminoxy acids to give aminoxyacyl amides 3a-g, (3e+3e'), and (3g+3g'), aminoxy hybrid peptides 4a-h, (4a+4a'), 6a-d, 9a-e, (9a+9a'), and (9b+9b'), and alpha-aminoxy peptides 10a,b in good yields without racemization.

Design, synthesis, and structure-activity relationship of a novel series of 2-aryl 5-(4-oxo-3-phenethyl-2-thioxothiazolidinylidenemethyl)furans as HIV-1 entry inhibitors.

We previously identified two small molecules targeting the HIV-1 gp41, N-(4-carboxy-3-hydroxy)phenyl-2,5-dimethylpyrrole 12 (NB-2) and N-(3-carboxy-4-chloro)phenylpyrrole 13 (NB-64), that inhibit HIV-1 infection at low micromolar levels. On the basis of molecular docking analysis, we designed a series of 2-aryl 5-(4-oxo-3-phenethyl-2-thioxothiazolidinylidenemethyl)furans. Compared with 12 and 13, these compounds have bigger molecular size (437-515 Da) and could occupy more space in the deep hydrophobic pocket on the gp41 NHR trimer. Fifteen 2-aryl 5-(4-oxo-3-phenethyl-2-thioxothiazolidinylidenemethyl)furans (11a-o) were synthesized by Suzuki-Miyaura cross-coupling followed by a Knoevenagel condensation and tested for their anti-HIV-1 activity and cytotoxicity on MT-2 cells. We found that all 15 compounds had improved anti-HIV-1 activity and 3 of them (11a, 11b, and 11d) exhibited inhibitory activity against replication of HIV-1(IIIB) and 94UG103 at <100 nM range, more than 20-fold more potent than 12 and 13, suggesting that these compounds can serve as leads for development of novel small molecule HIV fusion inhibitors.

Selective synthesis and structural elucidation of S-acyl- and N-acylcysteines.

N-(Acyl)-1H-benzotriazoles 6a-f react with l-cysteine 5 at 20 degrees C to give exclusively (i) N-acyl-l-cysteines 8a-e in the presence of triethylamine in CH(3)CN-H(2)O (3:1), but (ii) S-acyl-l-cysteines 7a-e in CH(3)CN-H(2)O (5:1) in the absence of base. Structures 7b, 7d and 8b, 8d are supported by 2D NMR spectroscopic methods including gDQCOSY, gHMQC, gHMBC, and (1)H-(15)N CIGAR-gHMBC experiments. The structure of compound 8d was also supported by single-crystal X-ray diffraction.

Convenient and efficient preparations of azodye-labeled peptides.

N-(4-Arylazobenzoyl)-1H-benzotriazoles 15a, 15b react with dipeptides 12a-d, (12d+12d') and tripeptides 14a, 14b to give azodye labeled-dipeptides (16a-e), (16d+16d'), (16e+16e') and -tripeptides 16f, 16g in high yields (73-93%) with retention of chirality.