1,3-Dimethyllumazine derivatives from Limnatis nilotica.

Two previously unknown lumazine derivatives, 1 and 2, have been isolated from the parasitic freshwater leech Limnatis nilotica. The structures of the compounds have been elucidated by NMR and unambiguously corroborated by chemical synthesis.

A modular strategy toward the synthesis of heparin-like oligosaccharides using monomeric building blocks in a sequential glycosylation strategy.

A novel flexible assembly strategy is described for the modular synthesis of heparin and heparan sulfates. The reported strategy uses monomeric building blocks to construct the oligosaccharide chain to attain a maximum degree of flexibility. In the assembly, 1-hydroxyl glucosazido- and 1-thio uronic acid donors are combined in a sequential glycosylation protocol using sulfonium triflate activator systems.

Chemically synthesized protein as tumour-specific vaccine: immunogenicity and efficacy of synthetic HPV16 E7 in the TC-1 mouse tumour model.

Many successful candidate vaccines capable of combating tumours in animal models come to an untimely end because of the costs associated with the approval and production of the GMP-grade materials, which are usually of biological origin, for use in humans. We have used a GMP-compatible method to chemically synthesize a pure synthetic E7 protein of the human papillomavirus type 16 (HPV16-E7). This oncogen-derived protein is constitutively expressed in cervical cancer and its precursors and is thus considered as an excellent target for tumour-specific immunity.

A practical synthesis of gramicidin s and sugar amino Acid containing analogues.

A practical gram-scale and high-yielding synthesis of the antimicrobial peptide gramicidin S is presented. An Fmoc-based solid-phase peptide synthesis protocol is employed for the generation of the linear decapeptide precursor, which is cyclized in solution to afford the target compound. The versatility of our method is demonstrated by the construction of eight gramicidin S analogues (15a-h) having nonproteinogenic sugar amino acid residues (4-7) incorporated in the turn regions.

Effective, high-yielding, and stereospecific total synthesis of D-erythro-(2R,3S)-sphingosine from D-ribo-(2S,3S,4R)-phytosphingosine.

The synthesis of naturally occurring D-erythro-(2R,3S,4E)-sphingosine from commercially available D-ribo-(2S,3S,4R)-phytosphingosine is described. The key step in the reaction sequence comprises TMSI/DBN promoted regio- and stereoselective oxirane opening of intermediate 2-phenyl-4-(S)-[(1S,2S)-1,2-epoxyhexadecyl]-1,3-oxazoline followed by the in situ trans-elimination of 2-phenyl-4-(S)-[(1S,2R)-1,2-dideoxy-2-iodo-1-trimethylsilyloxyhexadecyl]-1,3-oxazoline.

Design, synthesis, and evaluation of sugar amino acid based inhibitors of protein prenyl transferases PFT and PGGT-1.

Eleven analogues of the C-terminal Ca(1)a(2)X motif found in natural substrates of the prenyl transferases PFT and PGGT-1 were synthesized and evaluated for their inhibition potency and selectivity against PFT and PGGT-1. Replacement of the central dipeptide part a(1)a(2) by a benzylated sugar amino acid resulted in a good and highly selective PFT inhibitor (8, IC(50) = 250 +/- 20 nM). The methyl ester of 8 (13) selectively inhibited protein farnesylation in cultured cells.

The beta-glucuronyl-based prodrug strategy allows for its application on beta-glucuronyl-platinum conjugates.

The use of platinum drugs in antitumour therapy is well established. An important drawback of these chemotherapeutics is the lack of selectivity for tumour cells, usually resulting in severe toxic side effects. A glucuronyl-platinum conjugate was designed and synthesised to test the compatibility of platinum compounds with beta-glucuronidase-based prodrug therapy.

Structure of an anti-Lewis X Fab fragment in complex with its Lewis X antigen.

The Lewis X trisaccharide is pivotal in mediating specific cell-cell interactions. Monoclonal antibody 291-2G3-A, which was generated from mice infected with schistosomes, has been shown to recognize the Lewis X trisaccharide. Here we describe the structure of the Fab fragment of 291-2G3-A, with Lewis X, to 1.

Surface plasmon resonance evaluation of various aminoglycoside-RNA hairpin interactions reveals low degree of selectivity.

Aminoglycoside antibiotics, which are able to selectively bind to RNA, are considered to be an important lead in RNA-targeting drug discovery. In this study, surface plasmon resonance (SPR) was employed to explore the interaction of aminoglycosides with known tobramycin-binding RNA hairpins (aptamers) and an unrelated RNA hairpin. It was established that aminoglycosides have multiple interactions with RNA hairpins.

Thioglycuronides: synthesis and application in the assembly of acidic oligosaccharides.

[reaction: see text] Partially protected thioglycuronic acids are prepared efficiently by chemo- and regioselective oxidation of the corresponding thioglycosides using the TEMPO/BAIB reagent combination. After esterification, the thioglycuronic acids proved to be useful as both donor and acceptor in sulfonium-mediated condensations toward acidic di- and trisaccharides.

Synthesis and in vitro evaluation of PNA-peptide-DETA conjugates as potential cell penetrating artificial ribonucleases.

We report the synthesis of novel artificial ribonucleases with potentially improved cellular uptake. The design of trifunctional conjugates 1a and 1b is based on the specific RNA-recognizing properties of PNA, the RNA-cleaving abilities of diethylenetriamine (DETA), and the peptide (KFF)(3)K for potential uptake into E. coli.

Synthesis and elaboration of functionalised carbohydrate-derived spiroketals.

The scope of a stereoselective three-step approach for the synthesis of sugar derived spiroketals is presented. The methodology consists of Grignard addition of vinyl- or allylmagnesium bromide to a carbohydrate lactone, followed by K-10 clay mediated glycosidation with a terminal alkenol and subsequent ring-closing metathesis of the resulting diene. The generality of this procedure is demonstrated by the synthesis of various pyranose- and furanose-derived spiroketals, as well as more advanced tricyclic spiroketal derivatives.

Effect of bulky lesions on DNA: solution structure of a DNA duplex containing a cholesterol adduct.

The three-dimensional solution structure of two DNA decamers of sequence d(CCACXGGAAC)-(GTTCCGGTGG) with a modified nucleotide containing a cholesterol derivative (X) in its C1 '(chol)alpha or C1 '(chol)beta diastereoisomer form has been determined by using NMR and restrained molecular dynamics. This DNA derivative is recognized with high efficiency by the UvrB protein, which is part of the bacterial nucleotide excision repair, and the alpha anomer is repaired more efficiently than the beta one. The structures of the two decamers have been determined from accurate distance constraints obtained from a complete relaxation matrix analysis of the NOE intensities and torsion angle constraints derived from J-coupling constants.

Design and synthesis of 2-acetamidomethyl derivatives of isofagomine as potential inhibitors of human lysosomal beta-hexosaminidases.

As part of a program towards the development of specific inhibitors of human lysosomal beta-hexosaminidase for use as chemical chaperones in therapy of G(M2) gangliosidosis related diseases, the synthesis of 2-acetamidomethyl derivatives of isofagomine has been undertaken. Key event in this synthesis is the conversion of a C-2 substituted gluconolactone derivative into the corresponding lactam, followed by reduction to the corresponding amine. The 1-N-imino-2 acetamidomethyl derivative 5 proved to be a rather selective inhibitor with a K(i) of 2.

A novel strategy towards the synthesis of orthogonally functionalised 4-aminoglycosides.

A tethered nucleophilic substitution strategy for the stereoselective introduction of axially oriented amino functions on suitably protected gluco- and mannopyranosides is presented. The obtained oxazine is a versatile building block, which after some manipulation, could be used in the construction of highly functionalised oligosaccharides.

A short route toward chiral, polyhydroxylated indolizidines and quinolizidines.

In this paper, a rapid route toward functionalized bicyclic alkaloids is presented. In only three steps, an easily accessible carbohydrate derivative was converted into iodomethyl indolizidine 13, which can equilibrate to the corresponding iodoquinolizidine 15. We provide strong evidence that this equilibration proceeds via an aziridinium ion intermediate.

The use of a mannitol-derived fused oxacycle as a combinatorial scaffold.

An efficient and high-yielding solid-phase synthesis of a small library of compounds containing a cis-fused pyranofuran structural motive is described. With use of the cheap and readily available D-(+)-mannitol, a highly functionalized sugar template was synthesized and immobilized on a solid support via an olefinic linker. Modification of this two-point molecular scaffold and subsequent ring-closing metathesis/cleavage gave access to a series of functionalized conformationally constrained fused oxacycles.

A targeted peptide nucleic acid to down-regulate mouse microsomal triglyceride transfer protein expression in hepatocytes.

Peptide nucleic acids (PNA's) have shown to hold potential as antisense drugs. In this study we have designed PNA drugs for the microsomal triglyceride transfer protein (MTP), which is known to play a critical role in the assembly of atherogenic lipoproteins, and have converted the most potent drug into a liver-targeted prodrug. First, we have synthesized three PNA sequences targeting domains on the mouse MTP mRNA, which were not involved in intrastrand base-pairing interactions as jugded from its secondary structure.

Automated parallel solid-phase synthesis and anticancer screening of a library of peptide-tethered platinum(II) complexes.

The automated parallel solid-phase synthesis of a 36-member library of peptide-tethered platinum(II) complexes is described. The identity and quality of each product were confirmed by mass spectrometry and (1)H NMR. Subsequently, each compound was screened for in vitro anticancer activity by treating the A2780 (human ovarian carcinoma) cell line with two concentrations of the drugs (100 and 10 microM) in quadruplicate.

The conformation of neurotensin bound to its G protein-coupled receptor.

G protein-coupled receptors (GPCRs) mediate the perception of smell, light, taste, and pain. They are involved in signal recognition and cell communication and are some of the most important targets for drug development. Because currently no direct structural information on high-affinity ligands bound to GPCRs is available, rational drug design is limited to computational prediction combined with mutagenesis experiments.

Conformational analysis of furanoid epsilon-sugar amino acid containing cyclic peptides by NMR spectroscopy, molecular dynamics simulation, and X-ray crystallography: evidence for a novel turn structure.

Sugar amino acids (SAAs) are useful building blocks for the design of peptidomimetics and peptide scaffolds. The three-dimensional structures of cyclic hybrid molecules containing the furanoid epsilon-SAA III and several amino acids were elucidated to study the preferred conformation of such an epsilon-SAA and its conformational influence on the backbone of cyclic peptides. NMR-based molecular dynamics simulations and empirical calculations of the cyclic tetramer 1, consisting of two copies of the SAA residue and two amino acids, revealed that it is conformationally restrained.

Transglycosidase activity of chitotriosidase: improved enzymatic assay for the human macrophage chitinase.

Chitotriosidase is a chitinase that is massively expressed by lipid-laden tissue macrophages in man. Its enzymatic activity is markedly elevated in serum of patients suffering from lysosomal lipid storage disorders, sarcoidosis, thalassemia, and visceral Leishmaniasis. Monitoring of serum chitotriosidase activity in Gaucher disease patients during progression and therapeutic correction of their disease is useful to obtain insight in changes in body burden on pathological macrophages.

The interaction of peptide-tethered platinum(II) complexes with DNA.

The sequence specificity and intensity of DNA damage induced by six peptide-tethered platinum complexes was compared to cisplatin and Pt(en)Cl(2). DNA damage was investigated in pUC19 plasmid and in intact HeLa cells, and quantitatively analyzed using a Taq DNA polymerase/linear amplification assay. The DNA sequence specificity of the peptide-platinum compounds was found to be very similar to cisplatin and Pt(en)Cl(2), with runs of consecutive guanines being the most intensely damaged sites.

Improvement of hepatocyte-specific gene expression by a targeted colchicine prodrug.

Colchicine, an established tubulin inhibitor, interferes with the trafficking of endocytotic vesicles and thereby promotes the escape of lysosome-entrapped compounds. To improve its potency and cell specificity, a targeted prodrug of colchicine was synthesized by conjugation to a high-affinity ligand (di-N(alpha),N(epsilon)-(5-(2-acetamido-2-deoxy-beta-D-galactopyranosyloxy)pentanomido)lysine, K(GalNAc)(2)) for the asialoglycoprotein receptor on parenchymal liver cells. The resulting colchicine-K(GalNAc)(2) conjugate bound to this receptor with an affinity of 4.

Synthesis and biological evaluation of novel turn-modified gramicidin S analogues.

The synthesis of novel gramicidin S analogues having additional functionalities in the turn region by employing a biomimetic approach is described. The preservation of beta-sheet character in all analogues was established by NMR and the biological activity was evaluated.