TY - JOUR A1 - Vankar, Yashwant D. A1 - Linker, Torsten T1 - Recent Developments in the Synthesis of 2-C-Branched and 1,2-Annulated Carbohydrates JF - European journal of organic chemistry N2 - The importance of carbohydrate chemistry in biological and medicinal chemistry has led to enormous developments in the synthesis of carbohydrate mimics. In this context, the synthesis of branched sugars in general and of 2-C-branched carbohydrates in particular, as well as the synthesis of 1,2-annulated sugars, have received immense attention. They serve not only as carbohydrate mimics in the form of stand-alone molecules, but also as useful intermediates in the synthesis of many natural products, their analogues, and glycosidase inhibitors. This microreview covers the recent synthetic efforts in this area and puts the subject matter into proper perspective for future developments. KW - Synthetic methods KW - Annulation KW - Carbohydrates KW - Carbohydrate mimics Y1 - 2015 U6 - https://doi.org/10.1002/ejoc.201501176 SN - 1434-193X SN - 1099-0690 IS - 35 SP - 7633 EP - 7642 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Schmidt, Bernd A1 - Hauke, Sylvia T1 - Metathesis-Based de novo synthesis of noviose JF - European journal of organic chemistry N2 - The rare carbohydrate L-(+)-noviose was synthesized from enantiomerically pure L-lactate. The configuration at C-4 was established by diastereoselective nucleophilic addition to an in-situ-generated lactaldehyde. The resulting homoallylic alcohol was further transformed into a set of ring-closing metathesis (RCM) precursors. These compounds were converted into noviose in few steps using RCM and RCM-allylic-oxidation sequences. KW - Carbohydrates KW - Allylic oxidation KW - Oxygen heterocycles KW - Metathesis KW - Ruthenium Y1 - 2014 U6 - https://doi.org/10.1002/ejoc.201301615 SN - 1434-193X SN - 1099-0690 VL - 2014 IS - 9 SP - 1951 EP - 1960 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Yin, Jian A1 - Linker, Torsten T1 - Stereoselective diversity-oriented syntheses of functionalized saccharides from bicyclic carbohydrate 1,2-lactones JF - Tetrahedron N2 - Bicyclic carbohydrate 1,2-lactones have been synthesized in only two steps and high yields by saponification and subsequent cyclization from known malonate addition products to glycals. The gluco-configured lactone serves as an important precursor for diversity-oriented syntheses. Thus, stereoselective opening of the lactone ring was realized with various nucleophiles in the presence of Sc(OTf)(3). This enabled the introduction of different substituents at the anomeric position, to afford a broad variety of 1-functionalized carbohydrates. On the other hand, stereoselective alpha-substitution of the gluco-configured lactone with different electrophiles and subsequent ring opening gives a collection of 2-functionalized saccharides. More than 30 products have been isolated in analytically pure form, and their configurations were unequivocally established by various NMR methods. Thus, carbohydrate 1,2-lactones are attractive precursors for the stereoselective synthesis of diverse saccharides. KW - Carbohydrates KW - Lactones KW - Glycosides KW - Molecular diversity KW - Synthetic methods Y1 - 2011 U6 - https://doi.org/10.1016/j.tet.2011.01.069 SN - 0040-4020 VL - 67 IS - 13 SP - 2447 EP - 2461 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Vidadala, Srinivasa Rao A1 - Pimpalpalle, Tukaram M. A1 - Linker, Torsten A1 - Hotha, Srinivas T1 - Gold-Catalyzed reactions of 2-C-Branched carbohydrates mild glycosidations and selective anomerizations JF - European journal of organic chemistry N2 - 2-C-branched methyl glycosides react with various alcohols under gold catalysis to transglycosylated products. The method is applicable for the convenient synthesis of disaccharides. Without nucleophile a selective anomerization occurs, giving first access to alpha-configured 2-C-nitromethyl glycosides. The results are interesting for the mechanism of gold-catalyzed glycosidations. KW - Anomerization KW - Carbohydrates KW - Glycosidation KW - Gold KW - Synthetic methods Y1 - 2011 U6 - https://doi.org/10.1002/ejoc.201100134 SN - 1434-193X IS - 13 SP - 2426 EP - 2430 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Kramer, Markus A1 - Kleinpeter, Erich T1 - A conformational study of N-acetyl glucosamine derivatives utilizing residual dipolar couplings JF - Journal of magnetic resonance N2 - The conformational analyses of six non-rigid N-acetyl glucosamine (NAG) derivatives employing residual dipolar couplings (RDCs) and NOEs together with molecular dynamics (MD) simulations are presented. Due to internal dynamics we had to consider different conformer ratios existing in solution. The good quality of the correlation between theoretically and experimentally obtained RDCs show the correctness of the calculated conformers even if the ratios derived from the MD simulations do not exactly meet the experimental data. If possible, the results were compared to former published data and commented. KW - NMR KW - Residual dipolar couplings KW - Molecular dynamics KW - N-acetyl glucosamine derivatives KW - Carbohydrates Y1 - 2011 U6 - https://doi.org/10.1016/j.jmr.2011.06.029 SN - 1090-7807 VL - 212 IS - 1 SP - 174 EP - 185 PB - Elsevier CY - San Diego ER - TY - THES A1 - Issaree, Arisara T1 - Synthesis of Hetero-chitooligosaccharides T1 - Synthese von Hetero-Chitooligosacchariden N2 - Chitooligosaccharides are composed of linear β-(1→4)-linked 2-acetamido-2-deoxy-β-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-β-D-glucopyranose (GlcN). They are of interest due to their remarkable biological properties including antibacterial, antitumor, antifungal and elicitor activities. They can be obtained from the aminoglucan chitosan by chemical or enzymatic degradation which obviously affords rather heterogenous mixtures. On the other hand, chemical synthesis provides pure compounds with defined sequences of GlcNAc and GlcN monomers. The synthesis of homo- and hetero-chitobioses and hetero-chitotetraoses is described in this thesis. Dimethylmaleoyl and phthaloyl groups were used for protection of the amines. The donor was activated as the trichloroacetimidate in order to form the β-linkages. Glycosylation in the presence of trimethylsilyl trifluoromethanesulfonate, followed by N- and O-deprotection furnished chitobioses and chitotetraoses in good yields. N2 - Chitooligosacchride bestehen aus linear β-(1→4)-verknüpften 2-acetamido-2-deoxy-β-D-glucopyranose (GlcNAc) and/or 2-amino-2-deoxy-β-D-glucopyranose (GlcN) Einheiten. Sie beanspruchen aufgrund ihrer bemerkenswerten biologischen Eigenschaften – u.a. antibakterielle, antitumor, antimykotische und Elicitor Aktivität - grosses Interesse. Sie sind durch chemischen oder enzymatischen Abbau von Chitosan zugänglich, wobei diese Methoden unausweichlich zu komplexen, sehr heterogenen Mischungen von Chiooligosacchariden führen. Chemische Synthesen von Chitooligosacchariden mit definierter Sequenz von GlcNAc und GlcN Einheiten sind daher von erheblichem Interesse. In der vorliegenden Arbeit werden Synthesen von partiell acetylierten Chitobiosen und –tetraosen beschrieben. Die Aminogruppen wurden als N-Dimethylmaleoyl- bzw. Phthaloylimide geschützt. Die Donoren wurden als Trichloacetimidate aktiviert, wobei aufgrund von Nachbargruppeneffekten ausschliesslich die β-Glycoside entstehen. Die Trimethylsilyltrifluoromethansulfonat-promovierte Glycosidierung geeigneter Akzeptoren lieferte schliesslich die Chitobiosen und die Chitotetraosen in guten Ausbeuten. KW - Kohlenhydrate KW - Chitooligosaccharide KW - Glycosylierung KW - Synthesemethoden KW - Trichloracetimidate KW - Carbohydrates KW - Chitooligosaccharides KW - Glycosylation KW - Synthetic methods KW - Trichloroacetimidates Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-17069 ER -