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Protein post-translational modifications (PTMs) play a critical role in the regulation of protein catalytic activity, localization, and protein-protein interactions. Attachment of PTMs onto proteins significantly diversifies their structure and function, resulting in proteoforms. However, the sole identification of post-translationally modified proteins, which are often cell type and disease-specific, is still a highly challenging task. Substoichiometric amounts and modifications of low abundant proteins necessitate the purification or enrichment of the modified proteins. Although the introduction of mass spectrometry-based chemical proteomic strategies has enabled the screening of protein PTMs with increased throughput, sample preparation remains highly time-consuming and tedious. Here, we report an optimized workflow for the enrichment of PTM proteins in a 96-well plate format, which could be extended to robotic automation. This platform allows us to significantly lower the input of total protein, which opens up the opportunity to screen specialized and difficult-to-culture cell lines in a high-throughput manner. The presented SP2E protocol is robust and time- and cost-effective, as well as suitable for large-scale screening of proteoforms. The application of the SP2E protocol will thus enable the characterization of proteoforms in various processes such as neurodevelopment, neurodegeneration, and cancer. This may contribute to an overall acceleration of the recently launched Human Proteoform Project.

To map the underlying molecular mechanisms of folding dynamics in proteins, light-operated peptides have emerged as promising tools. In this study, we reveal the complete sequence of light-induced structural changes of AzoChignolin, a short β-hairpin peptide containing an azobenzene photoswitch in its loop region. Light-triggered structural changes were monitored by time-resolved IR spectroscopy. Formation and destruction of the hairpin structure is very fast and occurs within 100 ns for AzoChignolin in methanol. Atomistic molecular dynamics simulations using two explicit solvents, methanol and water, revealed the underlying molecular processes and allowed us to gain further insight into the reaction mechanism. Despite its rapid reaction time, hairpin formation in these solvents is not force-driven by the molecular switch but proceeded via formation of interstrand hydrogen bonds and contacts between aromatic residues. Moreover, the combined experimental and theoretical study demonstrates that the solvent (methanol vs water) does not dictate the velocity of β-hairpin formation in the AzoChignolin peptide comprising only a few hydrophobic residues in the strands.

Protein post-translational modifications (PTMs) play a critical role in the regulation of protein catalytic activity, localization and protein-protein interactions. Attachment of PTMs onto proteins significantly diversifies their structure and function resulting in so-called proteoforms. However, the sole identification of post-translationally modified proteins, which are often cell type and disease specific, is still a highly challenging task. Sub-stoichiometric amounts and modification of low abundant proteins necessitate purification or enrichment of the modified proteins. Although the introduction of the mass spectrometry-based chemical proteomic strategies have enabled to screen protein PTMs with increased throughput, sample preparation has remained highly time consuming and tedious. Here, we report an optimized workflow for enrichment of PTM proteins in 96-well plate format which can be possible extended to robotic automatization. This platform allows to significantly lower the input of total protein, which opens up the opportunity to screen specialized and difficult to culture cell lines in high-throughput manner. The presented SP2E protocol is robust, time- and cost-effective as well as suitable for large-scale screening of proteoforms. Application of the SP2E protocol will thus enable the characterization of proteoforms in various processes such as neurodevelopment, neurodegeneration and cancer and may contribute to an overall acceleration of the recently launched Human Proteoform Project.

Lanmodulin (LanM), a naturally lanthanide (Ln)-binding protein with a remarkable selectivity for Lns over Ca(II ) and affinities in the picomolar range, is an attractive target to address challenges in Ln separation. Why LanM has such a high selectivity is currently not entirely understood; both specific amino acid sequences of the EF-Hand loops and cooperativity effects have been suggested. Here, we removed the effect of cooperativity and synthesised all four 12-amino acid EF-Hand loop peptides, and investigated their affinity for two Lns (Eu( III) and Tb(III)), the actinide Cm(III) and Ca(II). Using isothermal titration calorimetry and time-resolved laser fluorescence spectroscopy (TRLFS) combined with parallel factor analysis, we show that the four short peptides behave very similarly, having affinities in the micromolar range for Eu(III) and Tb(III). Ca(II) was shown not to bind to the peptides, which was verified with circular dichroism spectroscopy. This technique also revealed an increase in structural organisation upon Eu(III) addition, which was supported by molecular dynamics simulations. Lastly, we put Eu(III) and Cm(III) in direct competition using TRLFS. Remarkably, a slightly higher affinity for Cm(III) was found. Our results demonstrate that the picomolar affinities in LanM are largely an effect of pre-structuring and therefore a reduction of flexibility in combination with cooperative effects, and that all EF-Hand loops possess similar affinities when detached from the protein backbone, albeit still retaining the high selectivity for lanthanides and actinides over calcium.

Since the discovery of the biological relevance of lanthanides (Lns) for methylotrophic bacteria in the last decade, the field has seen a steady rise in discoveries of bacteria using Lns. The major role of lanthanides here is in the active sites of enzymes: methanol dehydrogenases. Additionally, lanthanide binding proteins have also been identified. One such protein is lanmodulin (LanM) and, with a remarkable selectivity for Lns over Ca(II) and affinities in the picomolar range, it makes an attractive target to address challenges in lanthanide separation. Why LanM has such a high selectivity is currently not entirely understood, both the specific amino acid sequences of the EF-hand loops, together with cooperativity effects have been suggested. Consequently, we decided to remove the effect of cooperativity by focusing on the amino acid level. Thus, we synthesized all four 12-amino acid EF-Hand loop peptides of LanM using solid phase peptide synthesis and investigated their affinity for Lns (Eu(III), Tb(III)), the actinide Cm(III) and Ca(II). Using isothermal titration calorimetry and time resolved laser fluorescence spectroscopy combined with parallel factor analysis, we show that in the absence of cooperativity the short EF-Hand loop peptides have all similar affinities for lanthanides and that these are all in the micromolar range. Furthermore, calcium was shown not to bind to the peptides which was verified with circular dichroism spectroscopy. This technique also revealed that the peptides undergo a change to a more ordered state when lanthanides are added. These experimental observations were further supported by molecular dynamics simulations. Lastly, we put Eu(III) and Cm(III) in direct competition using TRLFS. Remarkably, a slightly higher affinity for the actinide, as was also observed for LanM, was found. Our results demonstrate that the picomolar affinities in LanM are largely an effect of pre-structuring in the full protein and therefore reduction of flexibility in combination with cooperative effects, and that all EF-Hand loops possess similar affinities when detached from the protein backbone, albeit still retaining the high selectivity for lanthanides and actinides over calcium.

Despite its potential importance for bacterial virulence, protein rhamnosylation has not yet been sufficiently studied. Specific anti-SerRha, anti-ThrRha and anti-AsnRha antibodies allowed the identification of previously unknown monorhamnosylated proteins in cytosol and membrane fractions of bacterial cell lysates. Mapping of the complete rhamnoproteome in pathogens should facilitate development of targeted therapies against bacterial infections.

The light triggered unfolding reaction of the azobenzene peptide AzoTrpZip2 is investigated from 1 ps to 100 µs. Absorption changes show that the unfolding is a multistep process with the initial breaking of the hydrogen bonds in the vicinity of the AMPP chromophore on the 1 ns time scale followed by the disappearance of the remaining interstrand hydrogen bonds of the native hairpin structure with a 1.9 µs process. Subsequently, the hydrophobic core structure still stabilising a hairpin-like pattern rearranges in a 17 µs process. The strong slowing down of this reaction at lower temperature points to a barrier height in the range of 60 kJ/mol.

Bearing in mind the often insufficient metabolic stability of carbohydrate antigens, which impairs both the bioavailability and immunogenicity of a given hapten, the development of chemically modified analogs with improved antigenicity is an important step towards effective glycoconjugate vaccines. Recently, strategic glycan fluorination has become an interesting approach to this, and several examples of fluorinated carbohydrate antigens that show better metabolic stabilities and comparable or even enhanced immunogenicities have been reported to date. In this paper, we present a small library of fluorinated trisaccharides based on a privileged motif from the lipophosphoglycan capping structure of Leishmania donovani, a protozoan parasite responsible for fatal visceral leishmaniasis. These epitope analogs were synthesized by a sequential [1+1+1] glycosylation strategy. An amine linker is present at the reducing end to allow conjugation and enable future applications in immunological studies for the development of diagnostic tools and vaccines.

α-Galactosylceramides are glycosphingolipids that show promise in cancer immunotherapy. After presentation by CD1d, they activate natural killer T cells (NKT), which results in the production of a variety of pro-inflammatory and immunomodulatory cytokines. Herein, we report the synthesis and biological evaluation of photochromic derivatives of KRN-7000, the activity of which can be modulated with light. Based on established structure-activity relationships, we designed photoswitchable analogues of this glycolipid that control the production of pro-inflammatory cytokines, such as IFN-γ. The azobenzene derivative α-GalACer-4 proved to be more potent than KRN-7000 itself when activated with 370 nm light. Photolipids of this type could improve our mechanistic understanding of cytokine production and could open new directions in photoimmunotherapy.

An operationally simple one-pot reaction for the preparation of a novel class of racemic trifluoromethylated 2,3-dihydro-1H-imidazoles derived from electron-poor N,O-acetals and aryl Grignard reagents is described. In addition, access to highly functionalized 2-trifluoromethyl-2,3-dihydro-1H-imidazoles was accomplished by reaction of N-aryl hemiaminal ethers and N-aryl trifluoroethylamines in the presence of an excess of n-butyllithium.

The decoding of the mechanisms underlying glycan-mediated recognition in disease and health requires access to structurally well-defined oligosaccharides as molecular probes. Owing to their often favourable properties, deoxyfluorosugars have emerged as a promising class of selectively modified carbohydrates for biological and immunological studies. In particular the enhanced metabolic stability and intrinsic immunogenicity of fluorinated carbohydrates has spurred research on their use for vaccine design. Herein, a first total synthesis of an orthogonally protected and fluorinated hexasaccharide-threonine conjugate of the natural sialophorin antigen has been accomplished. Starting from readily available monosaccharide building blocks, the targeted glycosyl amino acid 1 was assembled by a [3+3']-block glycosylation strategy. Together with its (1. 4)-linked regioisomer the glycan mimic can be applied to solid-phase glycopeptide synthesis to access novel sialophorin-derived molecular tools for functional and biomedical studies.

Much research effort has been devoted to the synthesis of fluorinated organic compounds in medicinal chemistry programs. For instance, incorporation of fluorine substituents and trifluoromethyl groups has become a widespread lead optimization strategy owing to the often favorable influence of such moieties on affinity and physicochemical properties. However, introduction of fluoroalkyl groups into dedicated positions of pharmacophores is synthetically challenging. In particular, efficient syntheses of di- and trifluoroethylamines are needed as they are an interesting, yet underrepresented, class of carboxamide mimics. Thus, a practical and reliable protocol for their preparation is described by using functionalized di- and trifluoromethylated N-aryl-substituted N,O-acetals as synthetic aldimine equivalents. Moreover, previously unknown -trifluoroethylamine analogs of 1,2-dihydroquinazolin-4(1H)-thione and the androgen receptor antagonist DIMN are prepared to demonstrate the method's applicability.

A variety of functionalized β-amino-β-fluoroalkyl carbonyl compounds are accessible via a novel one-pot Mannich-type reaction of CF 2 - and CF 3 -containing N -aryl N , O -acetals with lithium enolates of ketones, esters, and nitriles. The resulting β-fluoroalkylated β-aminocarbonyl compounds are promising peptide surrogates to be used in drug development and for biological applications.

Inkretin-Mimetika sind auf dem besten Weg, sich zu einer tragenden Saule in der Typ-2-Diabetes-Behandlung zu entwickeln. Durch ihre Wirkung auf die Bauchspeicheldruse und das Gehirn verstarken sie die Insulinsekretion, induzieren einen Gewichtsverlust und halten die Normoglykamie aufrecht. Allerdings wird die Inkretin-Therapie mit Nebenwirkungen wie Ubelkeit und Magen-Darm-Storungen in Verbindung gebracht. Hier stellen wir ein neuartiges photoschaltbares Inkretin-Mimetikum vor, das auf Liraglutid, einem spezifischen Agonisten des Glucagon-artigen Peptid-1-Rezeptors (GLP-1R), basiert. Dieses Peptid, genannt LirAzo, enthalt eine Azobenzoleinheit, wodurch der GLP-1R mit Lichtempfindlichkeit und isomerabhangigen Signaleigenschaften ausgestattet wird. Wahrend das trans-Isomer in erster Linie den Ca2+-Einstrom in das Zytosol beeinflusst, begunstigt das cis-Isomer vorwiegend die Bildung von cAMP. Somit ermoglicht LirAzo die optische Kontrolle der Insulinsekretion und des Zellenuberlebens.

The synthesis of novel, chignolin-derived peptides comprising the azobenzene photoswitch [3-(3-aminomethyl)phenylazo]phenylacetic acid (AMPP) is reported. Reversible photoswitching behavior led to folding into β-hairpin-like structures, as unequivocally demonstrated by CD, FT-IR and NMR spectroscopy.

The development of selective anticancer vaccines that provide enhanced protection against tumor recurrence and metastasis has been the subject of intense research in the scientific community. The tumor-associated glycoprotein MUC1 represents a well-established target for cancer immunotherapy and has been used for the construction of various synthetic vaccine candidates. However, many of these vaccine prototypes suffer from an inherent low immunogenicity and are susceptible to rapid in vivo degradation. To overcome these drawbacks, novel fluorinated MUC1 glycopeptide-BSA/TTox conjugate vaccines have been prepared. Immunization of mice with the 4’F-TF-MUC1-TTox conjugate resulted in strong immune responses overriding the natural tolerance against MUC1 and producing selective IgG antibodies that are cross-reactive with native MUC1 epitopes on MCF-7 human cancer cells.

Understanding the activation and internalization of G protein-coupled receptors (GPCRs) using conditional approaches is paramount to developing new therapeutic strategies. Here, we describe the design, synthesis, and testing of ExONatide, a benzylguanine-linked peptide agonist of the glucagon-like peptide-1 receptor (GLP-1R), a class B GPCR required for maintenance of glucose levels in humans. ExONatide covalently binds to SNAP-tagged GLP-1R-expressing cells, leading to prolonged cAMP generation, Ca2+ rises, and intracellular retention of the receptor. These effects were readily switched OFF following cleavage of the introduced disulfide bridge using the cell-permeable reducing agent beta-mercaptoethanol (BME). A similar approach could be extended to a class A GPCR using GhrelON, a benzylguanine-linked peptide agonist of the growth hormone secretagogue receptor 1a (GHS-R1a), which is involved in food intake and growth. Thus, ExONatide and GhrelON allow SNAP-tag-directed activation of class A and B GPCRs involved in gut hormone signaling in a reversible manner. This tactic, termed reductively cleavable agONist (RECON), may be useful for understanding GLP-1R and GHS-R1a function both in vitro and in vivo, with applicability across GPCRs., SNAP-tag-directed activation of class A and B G protein-coupled receptors can be achieved in a conditional and reversible manner using peptidic reductively cleavable agONists (RECONs).

This paper deals with pattern formation in Langmuir monolayers of two sets of lipid mixtures that include (1) a fluorinated lipid for phase separation, (2) a polymerizable lipid for stabilization of the patterned structure, and (3) a unit for the presentation of biological recognition units. Differences in the distribution of these functionalities allow a polymerization of dispersed or continuous phase and a placement of the recognition units in crystalline or solid analogue phase. Also, a ternary mixture including a lipid modified with the tandem repeat domain of MUC1 plus a TN-antigen was studied. Based on the biphasic pattern obtained (starlike crystals of up to 50 μm with a fine structure of some micrometers), we also verified the potential of the laterally patterned monolayer to stimulate the immune system (quartz crystal microbalance). The second set of lipids combines a highly fluorinated itaconic ester (polymerizable unit) with the natural phospholipid 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine.

With their unique ability for substrate recognition and their sequence-specific self-assembly properties, peptides play an important role in controlling the mineralization of inorganic materials in natural systems and in controlling the assembly of soft materials into complex structures required for biological functions. Here we report the use of an engineered heptapeptide that can differentiate between the crystalline anhydrous polymorphs of calcium carbonate. This peptide contains the positively charged amino acid arginine as well as proline rather than the prototypical negatively charged aspartate or glutamate units. Its affinity to vaterite compared to aragonite was demonstrated by fluorescence microscopy using biotinylated peptides. Crystallization experiments in the presence of the vaterite-affine peptide afforded only vaterite, whereas a mutant peptide, where a proline residue was replaced by glycine, exclusively leads to the formation of calcite.

The synthesis of a variety of α-branched trifluoroethyl amines was achieved by reaction of N-aryl hemiaminal ethers with organomagnesium reagents.

MUC1-type glycopeptides have already shown their potential as possible cancer vaccine candidates. In addition, first examples of fluorinated antigen structures, especially containing the Thomsen–Friedenreich antigen, with similar antibody recognition have been reported. Using microreactor techniques for improvement of the crucial step, the complex glycosylation reactions, is an efficient way to find optimized reaction parameter as well as to circumvent well-known scale-up drawbacks. Besides, this is the first report of continuous flow glycosylations of glycosyl amino acids, in particular with fluorinated glycosyl building blocks.

The analysis of humoral immune responses is of great importance for basic and clinical research. Mapping the structural requirements of epitope recognition with modified tumor-associated carbohydrate antigens allows both the development of biomarkers and the design of synthetic anticancer vaccines. For this purpose, double-tailed hydrocarbon/fluorocarbon membrane anchors have been prepared and conjugated to a TN dipeptide. Furthermore, a novel hydrophobized MUC1 tandem repeat glycopeptide antigen was fully assembled on a solid support and its specific binding to different mouse anti-MUC1 antibodies was demonstrated through ELISA, QCM, and SPR measurements. Such functional fluorous MUC1 antigens are of great interest for specific glycan (micro-)array formats and allow a detailed analyses of serum antibodies obtained from immunization studies. In addition, the intriguing characteristics of fluorous surfactants, for example, their strong self-association tendency, might stimulate the use of novel fluorous-tagged antigen conjugates in the development of multivalent micellar glycopeptide vaccines.

This paper describes the phase separating behavior of Langmuir monolayers from mixtures of different lipids that (i) either carry already a glycopeptide recognition site or can be easily modified to carry one and (ii) polymerizable lipids. To ensure demixing during compression, we used fluorinated lipids for the biological headgroups and hydrocarbon based lipids as polymerizable lipids. As a representative for a lipid monomer, which can be polymerized in the hydrophilic headgroup, a methacrylic monomer was used. As a monomer, which can be polymerized in the hydrophobic tail, a lipid with a diacetylene unit was used (pentacosadiynoic acid, PDA). The fluorinated lipids were on the one hand a perfluorinated lipid with three chains and on the other hand a partially fluorinated lipid with a T(N)-antigen headgroup. The macroscopic phase separation was observed by Brewster angle microscopy, whereas the phase separation on the nanoscale level was observed by atomic force microscopy. It turned out that all lipid mixtures showed (at least) a partial miscibility of the hydrocarbon compounds in the fluorinated compounds. This is positive for pattern formation, as it allows the formation of small demixed 2D patterned structures during crystallization from the homogeneous phase. For miscibility especially a liquid analogue phase proved to be advantageous. As lipid 3 with three fluorinated lipid chains (very stable monolayer) is miscible with the polymerizable lipids 1 and 2, it was mostly used for further investigations. For all three lipid mixtures, a phase separation on both the micrometer and the nanometer level was observed. The size of the crystalline domains could be controlled not only by varying the surface pressure but also by varying the molar composition of the mixtures. Furthermore, we showed that the binary mixture can be stabilized via UV polymerization. After polymerization and subsequent expansion of the barriers, the locked-in polymerized structures are stable even at low surface pressures (10 mN/m), where the unpolymerized mixture did not show any segregation.

Partial structures of tumor-associated mucin glycoproteins are interesting target structures for the development of selective anticancer vaccines. To probe the effect of fluorination on the immunological and metabolic properties of mucin glycopeptides, six novel fluorinated glycosyl-threonine conjugates have been synthesized. The synthesis of the orthogonally protected glycosyl amino acids was achieved using microwave irradiation in key fluorination and glycosylation steps. The 2'-deoxy-2'-fluoro- and 6'-deoxy-6'-fluoro-T antigen building blocks were applied to the synthesis of analogues of MUC1 tandem repeat-glycopeptide antigens via SPPS.

A stereoselective synthesis of the tetrahydrofuran-containing natural products (2 S ,5 R )-(+)-linalool oxide ( 1 ), (−)-isocyclocapitelline ( 2 ), and (−)-isochrysotricine ( 3 ) is reported. Key steps are the copper-mediated S N 2′-substitution of propargyl oxiranes 7 and the gold-catalyzed cycloisomerization of dihydroxyallenes 8 / 17 , resulting in a highly efficient center-to-axis-to-center chirality transfer. The enantioselective total synthesis of (−)-isocyclocapitelline ( 2 ) and (−)-isochrysotricine ( 3 ) allowed the elucidation of the absolute configuration of these β-carboline natural products.

The gold-catalyzed endo-cycloisomerization of allenes bearing nucleophilic substituents in the α- or β-position opens up a versatile access to various five- and six-membered heterocycles. Key features of these transformations are the high reactivity of the allene in the presence of Lewis-acidic, carbophilic gold(I) or gold(III) catalysts, and the chirality transfer from the allenic axis of chirality to the new stereogenic center in the cyclization product. Recent contributions of our group include the optimization of chirality transfer by using σ-donor ligands to gold, and applications in the total synthesis of natural products, e.g., of the β-carboline alkaloids (-)-isocyclocapitelline and (-)-isochrysotricine.

This review describes simple and useful concepts for predicting and tuning the pK(a) values of basic amine centers, a crucial step in the optimization of physical and ADME properties of many lead structures in drug-discovery research. The article starts with a case study of tricyclic thrombin inhibitors featuring a tertiary amine center with pK(a) values that can be tuned over a wide range, from the usual value of around 10 to below 2 by (remote) neighboring functionalities commonly encountered in medicinal chemistry. Next, the changes in pK(a) of acyclic and cyclic amines upon substitution by fluorine, oxygen, nitrogen, and sulfur functionalities, as well as carbonyl and carboxyl derivatives are systematically analyzed, leading to the derivation of simple rules for pK(a) prediction. Electronic and stereoelectronic effects in cyclic amines are discussed, and the emerging computational methods for pK(a) predictions are briefly surveyed. The rules for tuning amine basicities should not only be of interest in drug-discovery research, but also to the development of new crop-protection agents, new amine ligands for organometallic complexes, and in particular, to the growing field of amine-based organocatalysis.

Incretin mimetics are set to become a mainstay of type 2 diabetes treatment. By acting on the pancreas and brain, they potentiate insulin secretion and induce weight loss to preserve normoglycemia. Despite this, incretin therapy has been associated with off‐target effects, including nausea and gastrointestinal disturbance. A novel photoswitchable incretin mimetic based upon the specific glucagon‐like peptide‐1 receptor (GLP‐1R) agonist liraglutide was designed, synthesized, and tested. This peptidic compound, termed LirAzo, possesses an azobenzene photoresponsive element, affording isomer‐biased GLP‐1R signaling as a result of differential activation of second messenger pathways in response to light. While the trans isomer primarily engages calcium influx, the cis isomer favors cAMP generation. LirAzo thus allows optical control of insulin secretion and cell survival.

A series of 16 tricyclic thrombin inhibitors was prepared by using the 1,3-dipolar cycloaddition of azomethine ylides derived from 3- or 4-hydroxyproline and 4-bromobenzaldehyde, with N-(4-fluorobenzyl)maleimide as the key step. The terminal pyrrolidine ring of the inhibitors was systematically substituted to explore the potential bioisosteric behavior of C-F, C-OH, and C-OMe residues pointing into the environment of the catalytic center of a serine protease. X-ray crystal structure analyses revealed a distinct puckering preference of this ring. Substitution by F, HO, and MeO has a strong effect on the basicity of the adjacent pyrrolidine nitrogen center which originates from two sigma-inductive pathways between this center and the electronegative O and F atoms. gem-Difluorination decreases the pKa value of this tertiary amine center to

Heute sind etwa 150 Naturstoffe mit Allen- oder Cumulen-Struktur bekannt. Die Chemie dieser Verbindungen hat sich als ein reizvolles und fruchtbares Gebiet erwiesen: Fortschritte in der Isolierung und Charakterisierung neuer allenischer Naturstoffe haben zur Etablierung effizienter Syntheseverfahren gefuhrt, die haufig einen Zugang zu enantiomerenreinen Produkten eroffneten. Wegen der oftmals beeindruckenden biologischen Eigenschaften allenischer Naturstoffe sind Allengruppierungen mittlerweile systematisch in pharmakologisch aktive Verbindungsklassen (Steroide, Prostaglandine, Aminosauren, Nucleoside) eingebaut worden. Diese funktionalisierten Allene weisen in vielen Fallen interessante Aktivitaten auf, beispielsweise als Mechanismus-inharente Enzyminhibitoren, Cytostatika oder antivirale Wirkstoffe. Eine grundlegende Voraussetzung fur weitere Entwicklungen auf diesem Gebiet ist die effiziente stereoselektive Synthese von Allenderivaten.

Titanium enolates of 3,4-dienoates 3 were formed by treatment with LDA and Cp 2 TiCl 2 and oxidized with dimethyl dioxirane to furnish the allenic hydroxyesters 4 with up to 90% diastereoselectivity. Smooth cyclization to the functionalized 2,5-dihydrofurans 5 was accomplished with complete axis to center chirality transfer by treatment with HCl gas in chloroform.

Regarding its many roles for lead optimization and drug development, fluorine will definitely continue to be of major importance in medicinal chemistry. With safe and selective fluorinating agents at hands, the use of fluorinated compounds has become routine in pharmaceutical and material sciences and many of the well-appreciated organofluorine inductive effects are now understood. In contrast, our knowledge of how fluorine affects binding affinity and selectivity of proteins and antibodies at the molecular level is by far less advanced. Thus, applications of fluorinated haptens and antigens in the mapping of binding epitopes for various antibodies of diagnostic and therapeutic relevance, as well as for the generation of immune modulating agents and ligands with enhanced T cell affinity are reviewed. Moreover, recent examples of vaccines against cocaine and cancer based on selectively fluorinated antigens with improved antigenic properties are presented.

The syntheses of various fluorinated MUC1 glycopeptide antigens and their specific binding to serum antibodies from mice immunized with natural and fluorinated TF(6)-MUC1-TTox conjugate vaccines are presented.

A novel MUC1-glycopeptide–BSA conjugate vaccine with a specifically fluorinated Thomsen–Friedenreich antigen side chain at Thr6 was prepared. Preliminary immunological experiments reveal specific binding of the tumor-associated glycopeptide antigen analog by anti-MUC1-mouse antibodies.

Selectively 6-fluorinated analogs of the tumor-associated T(N) antigen Fmoc-Thr(α-O-GalNAc)-OtBu can be efficiently prepared using DAST-mediated de(hydr)oxyfluorination reactions of preformed and orthogonally protected glycosyl amino esters without affecting the labile protecting groups and O-glycosidic linkages. The resulting mono- and difluorinated T(N) analogs are interesting building blocks for non-hydrolyzable mucin-type antigen mimetics, as illustrated by the unprecedented synthesis of two different multiply fluorinated Thomsen-Friedenreich derivatives. The reported deoxyfluoro antigen analogs represent important functional probes for carbohydrate-binding proteins and glycosyl-processing enzymes.

The synthesis of perfluoroalkylated glycopeptide antigens and their specific binding to anti-MUC1 mouse antibodies is reported.

The aberrant glycosylation profiles of mucin glycoproteins on epithelial tumour cells represent attractive target structures for the development of immunotherapy against cancer. Mucin-type glycopeptides have been successfully investigated as molecularly defined vaccine prototypes for triggering humoral immunity but are susceptible to rapid in vivo degradation. As a potential means to enhance the bioavailabilities of the antigenic structures, hydrolysis-resistant carbohydrate analogues with fluorine substituents at positions C6, C2' and C6' were synthesised and incorporated into the tandem repeat sequence of the mucin MUC1. The resulting pseudo-glycopeptides can be used to elucidate the effects of chemically modified antibody determinants on metabolic and immunological properties.

Whereas the cycloisomerization of phenyl-substituted α-hydroxyallene 1 to 2,5-dihydrofuran 2 catalyzed by gold(I) or gold(III) chloride takes place with considerable epimerization, high levels of axis-to-center chirality transfer can be reached in the -presence of additives (e.g. 2,2′-bipyridine), by using a moderately coordinating solvent (e.g. THF), or by lowering the reaction temperature. The increased stability and selectivity of the catalysts thus formed allows their application to the cycloisomerization of various functionalized α- and β-hydroxyallenes, as well as a decrease of the catalyst loading to 0.1%.

The use of functionalized aryl-Grignard reagents in the copper-mediated S N 2′ substitution of propargylic oxiranes leads to structurally complex α-hydroxyallenes, usually with high yield and diastereoselectivity. Further transformations, such as gold-catalyzed cycloisomerization to 2,5-dihydrofurans and palladium-catalyzed coupling reactions, demonstrate the high potential of these compounds for the rapid generation of molecular complexity.

The α-hydroxylation of zirconiumallenyl enolates, obtained from β-allenic esters by deprotonation with LDA or LiN(SiMe 3 ) 2 and transmetalation with Cp 2 ZrCl 2 , with dimethyldioxirane (DMDO) selectively affords 2-hydroxy-3,4-dienoates. The oxidation proceeds usually with high yield and substrate conversion and tolerates even sensitive or unreactive substrates.