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Publikation

Hussain, H.; Rashan, L.; Hassan, U.; Abbas, M.; Hakkim, F. L.; Green, I. R.; Frankincense diterpenes as a bio-source for drug discovery Expert Opinion on Drug Discovery 17, 513-529, (2022) DOI: 10.1080/17460441.2022.2044782

Introduction Frankincense (Boswellia sp.) gum resins have been employed as an incense in cultural and religious ceremonies for many years. Frankincense resin has over the years been employed to treat depression, inflammation, and cancer in traditional medicines. Areas coveredThis inclusive review focuses on the significance of frankincense diterpenoids, and in particular, incensole derivatives for establishment future treatments of depression, neurological disorders, and cancer. The authors survey the available literature and furnish an overview of future perspectives of these intriguing molecules. Expert opinion Numerous diterpenoids including cembrane, prenylaromadendrane, and the verticillane-type have been isolated from various Boswellia resins. Cembrane-type diterpenoids occupy a crucial position in pharmaceutical chemistry and related industries because of their intriguing biological and encouraging pharmacological potentials. Several cembranes have been reported to possess anti-Alzheimer, anti-inflammatory, hepatoprotective, and antimalarial effects along with a good possibility to treat anxiety and depression. Although some slight drawbacks of these compounds have been noted, including the selectivity of these diterpenoids, there is a great need to address these in future research endeavors. Moreover, it is vitally important for medicinal chemists to prepare libraries of incensole-heterocyclic analogs as well as hybrid compounds between incensole or its acetate and anti-depressant or anti-inflammatory drugs.
Publikation

Kaluđerović, G. N.; Abbas, M.; Kautz, H. C.; Wadaan, M. A. M.; Lennicke, C.; Seliger, B.; Wessjohann, L. A.; Methionine and seleno-methionine type peptide and peptoid building blocks synthesized by five-component five-center reactions Chem. Commun. 53, 3777-3780, (2017) DOI: 10.1039/C7CC00399D

A first example of 5-component 5-center reactions with isonitriles [Ugi-5CRs] is described. The extended Ugi type reactions involve selenoaldehydes as well as ammonia, both challenging reactants in multicomponent (MCR) systems, to generate methionine and Se-methionine moieties and derivatives as protected building blocks or for direct ligation in peptides or peptoids. The peptoid/peptide building blocks proved to be non-cytotoxic but increased the expression of genes encoding for stress protective selenoproteins (Gpx1).
Publikation

van Berkel, S. S.; Brauch, S.; Gabriel, L.; Henze, M.; Stark, S.; Vasilev, D.; Wessjohann, L. A.; Abbas, M.; Westermann, B.; “Spurlose” Tosylhydrazon-basierte Triazolsynthese: eine metallfreie Alternative zur ringspannungskatalysierten Azid-Alkin-Cycloaddition Angew. Chem. 124, 5437-5441, (2012) DOI: 10.1002/ange.201108850

Durch Reaktion primärer Amine mit funktionalisierten α,α‐Dichlortosylhydrazonen unter milden Bedingungen gelingt eine „spurlose“ Tosylhydrazon‐basierte Triazolsynthese, die ausschließlich zur Bildung 1,4‐substituierter Triazol‐„Klick‐Produkte“ unter vollständigem Konfigurationserhalt am Stereozentrum führt. Primäre Amine, die in vielen Naturstoffen vorkommen, können chemoselektiv ohne die Notwendigkeit einer umfassenden Schutzgruppenstrategie modifiziert werden.
Publikation

van Berkel, S. S.; Brauch, S.; Gabriel, L.; Henze, M.; Stark, S.; Vasilev, D.; Wessjohann, L. A.; Abbas, M.; Westermann, B.; Traceless Tosylhydrazone-Based Triazole Formation: A Metal-Free Alternative to Strain-Promoted Azide-Alkyne Cycloaddition Angew. Chem. Int. Ed. 51, 5343-5346, (2012) DOI: 10.1002/anie.201108850

Triple‐T trick! Traceless tosylhydrazone‐based triazole formation is readily achieved by reacting primary amines with functional α,α‐dichlorotosylhydrozones under ambient conditions. This fast and efficient alternative affords exclusively 1,4‐substituted triazole “click products” with complete retention of configuration. Primary amines, inherent to many natural products, can be modified in this way without protecting group manipulations.
Publikation

Abbas, M.; Wessjohann, L. A.; Direct synthesis of sensitive selenocysteine peptides by the Ugi reaction Org. Biomol. Chem. 10, 9330-9333, (2012) DOI: 10.1039/C2OB26552D

Ammonia and selenoaldehydes are both problematic components in Ugi reactions. Here we report the efficient direct multicomponent synthesis of sensitive selenocysteinepeptides without the use of convertible (protected) primary amines, including suitable deprotection protocols for selenols.
Publikation

Dubberke, S.; Abbas, M.; Westermann, B.; Oxidative allylic rearrangement of cycloalkenols: Formal total synthesis of enantiomerically pure trisporic acid B Beilstein J. Org. Chem. 7, 421-425, (2011) DOI: 10.3762/bjoc.7.54

Enantiomerically highly enriched unsaturated β-ketoesters bearing a quaternary stereocenter can be utilized as building blocks for the synthesis of natural occurring terpenes, i. a., trisporic acid and its derivatives. An advanced building block has been synthesized in a short reaction sequence, which involves an oxidative allylic rearrangement initiated by pyridinium dichromate (PDC) as the key step.
Publikation

Doering, M.; Ba, L. A.; Lilienthal, N.; Nicco, C.; Scherer, C.; Abbas, M.; Zada, A. A. P.; Coriat, R.; Burkholz, T.; Wessjohann, L.; Diederich, M.; Batteux, F.; Herling, M.; Jacob, C.; Synthesis and Selective Anticancer Activity of Organochalcogen Based Redox Catalysts J. Med. Chem. 53, 6954-6963, (2010) DOI: 10.1021/jm100576z

Many tumor cells exhibit a disturbed intracellular redox state resulting in higher levels of reactive oxygen species (ROS). As these contribute to tumor initiation and sustenance, catalytic redox agents combining significant activity with substrate specificity promise high activity and selectivity against oxidatively stressed malignant cells. We describe here the design and synthesis of novel organochalcogen based redox sensor/effector catalysts. Their selective anticancer activity at submicromolar and low micromolar concentrations was established here in a range of tumor entities in various biological systems including cell lines, primary tumor cell cultures, and animal models. In the B-cell derived chronic lymphocytic leukemia (CLL), for instance, such compounds preferentially induce apoptosis in the cancer cells while peripheral blood mononuclear cells (PBMC) from healthy donors and the subset of normal B-cells remain largely unaffected. In support of the concept of sensor/effector based ROS amplification, we are able to demonstrate that underlying this selective activity against CLL cells are pre-existing elevated ROS levels in the leukemic cells compared to their nonmalignant counterparts. Furthermore, the catalysts act in concert with certain chemotherapeutic drugs in several carcinoma cell lines to decrease cell proliferation while showing no such interactions in normal cells. Overall, the high efficacy and selectivity of (redox) catalytic sensor/effector compounds warrant further, extensive testing toward transfer into the clinical arena.
Publikation

Shabaan, S.; Ba, L. A.; Abbas, M.; Burkholz, T.; Denkert, A.; Gohr, A.; Wessjohann, L. A.; Sasse, F.; Weber, W.; Jacob, C.; Multicomponent reactions for the synthesis of multifunctional agents with activity against cancer cells Chem. Commun. 4702, (2009) DOI: 10.1039/B823149D

Multicomponent Passerini and Ugi reactions enable the fast and efficient synthesis of redox-active multifunctional selenium and tellurium compounds, of which some show considerable cytotoxicity against specific cancer cells.
Publikation

Mecklenburg, S.; Shaaban, S.; Ba, L. A.; Burkholz, T.; Schneider, T.; Diesel, B.; Kiemer, A. K.; Röseler, A.; Becker, K.; Reichrath, J.; Stark, A.; Tilgen, W.; Abbas, M.; Wessjohann, L. A.; Sasse, F.; Jacob, C.; Exploring synthetic avenues for the effective synthesis of selenium- and tellurium-containing multifunctional redox agents Org. Biomol. Chem. 7, 4753, (2009) DOI: 10.1039/B907831B

Various human illnesses, including several types of cancer and infectious diseases, are related to changes in the cellular redox homeostasis. During the last decade, several approaches have been explored which employ such disturbed redox balances for the benefit of therapy. Compounds able to modulate the intracellular redox state of cells have been developed, which effectively, yet also selectively, appear to kill cancer cells and a range of pathogenic microorganisms. Among the various agents employed, certain redox catalysts have shown considerable promise since they are non-toxic on their own yet develop an effective, often selective cytotoxicity in the presence of the ‘correct’ intracellular redox partners. Aminoalkylation, amide coupling and multicomponent reactions are suitable synthetic methods to generate a vast number of such multifunctional catalysts, which are chemically diverse and, depending on their structure, exhibit various interesting biological activities.
Publikation

Wessjohann, L. A.; Schneider, A.; Abbas, M.; Brandt, W.; Selenium in chemistry and biochemistry in comparison to sulfur Biol. Chem. 388, 997-1006, (2007) DOI: 10.1515/BC.2007.138

What makes selenoenzymes – seen from a chemist's view – so special that they cannot be substituted by just more analogous or adapted sulfur proteins? This review compiles and compares physicochemical properties of selenium and sulfur, synthetic routes to selenocysteine (Sec) and its peptides, and comparative studies of relevant thiols and selenols and their (mixed) dichalcogens, required to understand the special role of selenium in selenoproteins on the atomic molecular level. The biochemically most relevant differences are the higher polarizability of Se- and the lower pKa of SeH. The latter has a strikingly different pH-dependence than thiols, with selenols being active at much lower pH. Finally, selected typical enzymatic mechanisms which involve selenocysteine are critically discussed, also in view of the authors' own results.
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