76
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Schmidt RR, Hoffmann AR. Polare 1,4‐Cycloadditionen, XI. Diastereogene Reaktionen zur Untersuchung des Reaktionsverlaufs von Cycloadditionen. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/cber.19741070110] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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77
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Schmidt RR, Schneider W, Karg J, Burkert U. Synthese von Heterocyclen durch Thermolyse von o‐substituierten aromatischen Diazonium‐Ionen. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/cber.19721050519] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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78
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Schmidt RR, Berrer R. Heterocyclische 8π‐Systeme, 11: 5
H
‐1, 4‐Dithiepine und Derivate. ACTA ACUST UNITED AC 2006. [DOI: 10.1002/cber.19761090827] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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79
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Jonke S, Liu KG, Schmidt RR. Solid-Phase Oligosaccharide Synthesis of a Small Library of N-Glycans. Chemistry 2006; 12:1274-90. [PMID: 16273561 DOI: 10.1002/chem.200500707] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Solid-phase oligosaccharide synthesis is based on a hydroxymethylbenzyl benzoate spacer linker which is connected to the Merrifield resin (1 P). Glycosylation was performed with O-glycosyl trichloroacetimidates of glucosamine, mannose, and galactose permitting chain extension (2e, 5e), branching (4b, 7b, 8b), and chain termination (3t, 6t, 9t) with the use of O-benzyl, O-benzoyl, and N-dimethylmaleoyl as permanent and O-fluorenylmethoxycarbonyl (Fmoc) and O-phenoxyacetyl (PA) as temporary protecting groups. The steps required on solid phase are i) glycosylation under TMSOTf catalysis, ii) selective cleavage of the temporary protecting groups, Fmoc with NEt3 and PA with 0.5 equivalents of NaOMe in CH2Cl2/MeOH, and iii) product cleavage from the resin with 4.0 equivalents of NaOMe in CH2Cl2/MeOH and following O-acetylation for convenient product isolation. Thus a highly successful synthesis of a small library of seventeen N-glycan structures was made possible comprising the N-glycan pentasaccharide core structure 53 and two further chain extended hexa- and heptasaccharide N-glycans with a glucosamine or a lactosamine residue, respectively, which is attached to one of the mannose residues of the core structure (56 and 59).
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80
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Streicher H, Geyer A, Schmidt RR. C-Disaccharides of Ketoses. Chemistry 2006; 2:502-510. [DOI: 10.1002/chem.19960020508] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/1995] [Indexed: 11/08/2022]
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81
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Schmidt RR, Grundler G. α-Verknüpfte Disaccharide aus O-(β-D-Glycopyranosyl)-trichloracetimidaten mit Trimethylsilyltrifluormethansulfonat als Katalysator. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.19820941019] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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82
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Schmidt RR, Grundler G. Synthese eines Tetrasaccharids der Core-Region von O-Glycoproteinen. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.19830951018] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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83
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Schmidt RR, Hoffmann M. C-α- und C-β-D-Glucopyranosyl-Derivate - Synthesen aus O-(α-D-Glucopyranosyl)trichloracetimidat. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.19830950513] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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84
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Schmidt RR, Abele W. Hetero-Diels-Alder-Reaktionen zur Synthese von Thromboxan-Zwischenstufen. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.19820940417] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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85
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86
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Miyata O, Schmidt RR. Kinetische Acidität von Methinprotonen und carbonylaktivierten Methylenprotonen. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.19820940832] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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87
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88
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Röhrig CH, Retz OA, Hareng L, Hartung T, Schmidt RR. A new strategy for the synthesis of dinucleotides loaded with glycosylated amino acids--investigations on in vitro non-natural amino acid mutagenesis for glycoprotein synthesis. Chembiochem 2005; 6:1805-16. [PMID: 16142818 DOI: 10.1002/cbic.200500079] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The in vitro non-natural amino acid mutagenesis method provides the opportunity to introduce non-natural amino acids site-specifically into proteins. To this end, a chemically synthesised aminoacylated dinucleotide is enzymatically ligated to a truncated suppressor transfer RNA. The loaded suppressor tRNA is then used in translation reactions to read an internal stop codon. Here we report an advanced and general strategy for the synthesis of the aminoacyl dinucleotide. The protecting group pattern developed for the dinucleotide facilitates highly efficient aminoacylation, followed by one-step global deprotection. The strategy was applied to the synthesis of dinucleotides loaded with 2-acetamido-2-deoxy-glycosylated amino acids, including N- and O-beta-glycosides and O- and C-alpha-glycosides of amino acids, thus enabling the extension of in vitro non-natural amino acid mutagenesis towards the synthesis of natural glycoproteins of high biological interest. We demonstrate the incorporation of the glycosylamino acids--although with low suppression efficiency--into the human interleukin granulocyte-colony stimulating factor (hG-CSF), as verified by the ELISA technique.
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89
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90
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Patterson S, Kotsianidis I, Almeida A, Politou M, Rahemtulla A, Matthew B, Schmidt RR, Cerundolo V, Roberts IAG, Karadimitris A. Human Invariant NKT Cells Are Required for Effective In Vitro Alloresponses. THE JOURNAL OF IMMUNOLOGY 2005; 175:5087-94. [PMID: 16210612 DOI: 10.4049/jimmunol.175.8.5087] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
NKT cells are a small subset of regulatory T cells conserved in humans and mice. In humans they express the Valpha24Jalpha18 invariant chain (hence invariant NKT (iNKT) cells) and are restricted by the glycolipid-presenting molecule CD1d. In mice, iNKT cells may enhance or inhibit anti-infectious and antitumor T cell responses but suppress autoimmune and alloreactive responses. We postulated that iNKT cells might also modulate human alloreactive responses. Using MLR assays we demonstrate that in the presence of the CD1d-presented glycolipid alpha-galactosylceramide (alphaGC) alloreactivity is enhanced (37 +/- 12%; p < 0.001) in an iNKT cell-dependent manner. iNKT cells are activated early during the course of the MLR, presumably by natural ligands. In MLR performed without exogenous ligands, depletion of iNKT cells significantly diminished the alloresponse in terms of proliferation (58.8 +/- 24%; p < 0.001) and IFN-gamma secretion (43.2 +/- 15.2%; p < 0.001). Importantly, adding back fresh iNKT cells restored the reactivity of iNKT cell-depleted MLR to near baseline levels. CD1d-blocking mAbs equally reduced the reactivity of the iNKT cell-replete and -depleted MLR compared with IgG control, indicating that the effect of iNKT cells in the in vitro alloresponse is CD1d-dependent. These findings suggest that human iNKT cells, although not essential for its development, can enhance the alloreactive response.
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91
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92
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Iga DP, Iga S, Schmidt RR, Buzas MC. Chemical synthesis of cholesteryl β-d-galactofuranoside and -pyranoside. Carbohydr Res 2005; 340:2052-4. [PMID: 16023624 DOI: 10.1016/j.carres.2005.06.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2005] [Accepted: 06/14/2005] [Indexed: 11/26/2022]
Abstract
Two isomeric cholesteryl galactosides, cholesteryl beta-D-galactofuranoside and -pyranoside, have been synthesized by the Koenigs-Knorr reaction. Glycosylation of cholesterol with 2,3,5,6-tetra-O-benzoyl-D-galactofuranosyl bromide, followed by Zemplén saponification with sodium methoxide, gave cholesteryl beta-D-galactofuranoside. By using 2,3,4,6-tetra-O-acetyl-D-galactopyranosyl bromide as the glycosyl donor, followed by alkaline hydrolysis, cholesteryl beta-D-galactopyranoside was obtained. The title compounds were characterized by their IR spectra and by their (1)H and (13)C NMR spectra. Structure considerations of the two cholesteryl galactosides correlated with data in the literature, thus confirming that cholesteryl beta-D-galactopyranoside is an antigenic lipid of Lyme disease agent, Borrelia burgdorferi.
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93
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Janssen S, Schmidt RR. Synthesis of Ganglioside Mimics for Binding Studies with Myelin‐Associated Glycoprotein (MAG)*. J Carbohydr Chem 2005. [DOI: 10.1080/07328300500176312] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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94
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Koch M, Stronge VS, Shepherd D, Gadola SD, Mathew B, Ritter G, Fersht AR, Besra GS, Schmidt RR, Jones EY, Cerundolo V. The crystal structure of human CD1d with and without alpha-galactosylceramide. Nat Immunol 2005; 6:819-26. [PMID: 16007090 DOI: 10.1038/ni1225] [Citation(s) in RCA: 311] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Accepted: 06/01/2005] [Indexed: 11/09/2022]
Abstract
The glycolipid alpha-galactosylceramide binds with high affinity to CD1d and stimulates natural killer T cells. Here we report the crystal structure of human CD1d in complex with synthetic alpha-galactosylceramide at a resolution of 3.0 A. The structure shows a tightly fit lipid in the CD1d binding groove, with the sphingosine chain bound in the C' pocket and the longer acyl chain anchored in the A' pocket. We also present the CD1d structure without lipid, which has a more open conformation of the binding groove, suggesting a dual conformation of CD1d in which the 'open' conformation is more able to load lipids. These structures provide clues as to how CD1 molecules load glycolipids as well as data to guide the design of new therapeutic agents.
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95
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Skropeta D, Schwörer R, Haag T, Schmidt RR. Asymmetric synthesis and affinity of potent sialyltransferase inhibitors based on transition-state analogues. Glycoconj J 2005; 21:205-19. [PMID: 15486453 DOI: 10.1023/b:glyc.0000045093.96413.62] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Inhibitors that are structurally related to the transition-state model of the proposed SN1-type mechanism of sialyl transfer, exhibit particularly high binding affinities to alpha(2-6)sialyltransferases. Furthermore, replacing the neuraminyl residue with a simple aryl or hetaryl ring and substituting the carboxylate group for a phosphonate moiety, improves both binding affinity and synthetic accessibility. Herein we report on the synthesis and inhibition of a wide range of novel, potent transition-state analogue based alpha(2-6)sialyltransferase inhibitors comprising a planar anomeric carbon, an increased distance between the anomeric carbon and the CMP leaving group, and at least two negative charges. We also present a short, efficient asymmetric synthesis of the most promising benzyl inhibitors, providing rapid access to large quantities of highly potent, stereochemically-pure (>96% de) inhibitors for further biological investigation (e.g.(R)-3b, Ki = 70 nM).
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96
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Biskup MB, Müller JU, Weingart R, Schmidt RR. New Methods for the Generation of Carbohydrate Arrays on Glass Slides and Their Evaluation. Chembiochem 2005; 6:1007-15. [PMID: 15861434 DOI: 10.1002/cbic.200400300] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Glycosides, having spacers functionalized with an aldehyde or a carboxylic group, were immobilized through reductive amination or amidation, respectively, onto amino-functionalized glass slides. Hybridization experiments with lectins exhibited very little nonspecific protein binding, hence precluding the necessity for the blocking of unreacted functional groups on the glass slide. The covalency and the concentration dependency of the sugar ligation to the glass slide were demonstrated; the reversibility and the selectivity of lectin-carbohydrate interactions were shown.
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97
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Pachamuthu K, Zhu X, Schmidt RR. Reversed Approach to S-Farnesylation and S-Palmitoylation: Application to an Efficient Synthesis of the C-Terminus of Lipidated Human N-Ras Hexapeptide. J Org Chem 2005; 70:3720-3. [PMID: 15845014 DOI: 10.1021/jo0482357] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
[reaction: see text] A general reversed approach is described to synthesize S-palmitoylated and S-farnesylated peptides via S(N)2 displacement of bromide by reaction of a thiol group containing lipid as nucleophile with bromoalanine-containing peptides as electrophile. By employing this approach, lipidated peptides, including characteristic partial structures of human Ras peptides, were synthesized in good yields. This method gives access to farnesylated, palmitoylated, and doubly lipidated peptides.
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98
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Tarnowski A, Retz O, Bär T, Schmidt RR. Synthesis of Sphingosine-1-phosphonate and Homosphingosine-1-phosphonate. European J Org Chem 2005. [DOI: 10.1002/ejoc.200400671] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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99
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Tanaka M, Rehfeldt F, Schneider MF, Gege C, Schmidt RR, Funari SS. Oligomer-to-polymer transition in short ethylene glycol chains connected to mobile hydrophobic anchors. Chemphyschem 2005; 6:101-9. [PMID: 15688653 DOI: 10.1002/cphc.200400336] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We studied the structure of short ethylene glycol (EG) chains with N repeating units (EGN, N = 3, 6, 9, 12, and 15) connected to hydrophobic dihexadecyl chains by means of a combination of differential scanning calorimetry (DSC) and small- and wide-angle X-ray scattering (SAXS/WAXS). These synthetic amphiphiles dispersed in water form planar lamellar stacks and hexagonal cylinders confining the EG chains to restricted geometries. Owing to the self-assembly of the anchoring points, the lateral density of EG chains in planar lamella can be quantitatively controlled. Furthermore, the chain-melting phase transition of the anchors enables us to "switch" the intermolecular distance reversibly. SAXS/WAXS results suggest that the shorter EG chains (N = 3, 6, and 9) assume a helical conformation in stacks of planar lamella. When the EG chains are further elongated (N = 12 and 15), the lamellar periodicities cannot be explained by a linear extrapolation of shorter oligomers, but can be interpreted well as polymer brushes following the scaling theorem. Such rich phase behaviors of EGN molecules can be used as a simple model of oligo/poly-saccharide chains on cell surfaces, which act not only as flexible repellers between neighboring cells but also as stable spacers for functional ligands.
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100
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Röhrig CH, Retz OA, Meergans T, Schmidt RR. In vitro non-natural amino acid mutagenesis using a suppressor tRNA generated by the cis-acting hepatitis delta virus ribozyme. Biochem Biophys Res Commun 2005; 325:731-8. [PMID: 15541351 DOI: 10.1016/j.bbrc.2004.10.086] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Indexed: 10/26/2022]
Abstract
In vitro non-natural amino acid mutagenesis requires aminoacyl-charged suppressor transfer RNAs which read an internal stop codon. For the synthesis of aminoacyl-tRNAs loaded with non-natural amino acids, T4 RNA ligase is used to ligate a chemically synthesised aminoacyl-dinucleotide to a truncated 74mer tRNA(-CA) lacking the two 3' end nucleotides. The 74mer tRNA(-CA) in turn is generated by run-off transcription from a linearised plasmid encoding the tRNA sequence under control of the T7 promoter. Transcripts with heterogeneous ends are commonly obtained, which interfere with subsequent reactions such as ligation or translation. Here we report an improved procedure for the generation and chromatographic purification of large amounts of homogeneous 3' end tRNA(-CA) by hepatitis delta virus ribozyme cis-cleavage and the first application of this tRNA to in vitro non-natural amino acid mutagenesis. Stop codon suppression is increased compared to conventionally synthesised suppressor tRNA; 2.5 microg of mutated protein was synthesised in a 50 microl batch reaction.
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