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Annalen der Chemie und Pharmacie 07/2007; 2007(24):3963 - 3976. · 3.10 Impact Factor
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ABSTRACT: A historical overview is presented on stereo-directing effects of cis- and trans-fused diol protective groups used on both donor and acceptor glycosides. Attention is focused on the use of cyclic carbonates and carbamates, diacetals and acetals and finally the special case of 1,2-O-orthoesters and 1,2-O-cyanoalkylidene functionalised residues.
Carbohydrate Research 03/2007; 342(3-4):419-29. · 2.33 Impact Factor
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ABSTRACT: The preparation of highly functionalized pyrrolidines by a tandem Staudinger/aza-Wittig/Ugi Three-Component Reaction (SAWU-3CR) is presented. The SAWU-3CR was applied on two different carbohydrate derived 4-azidopentanals and two libraries of chemically diverse products were prepared.
QSAR & Combinatorial Science 05/2006; 25(5‐6):491 - 503. · 1.55 Impact Factor
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ABSTRACT: [reaction: see text] The natural product pachastrissamine, an anhydrophytosphingosine derivative isolated from various sponges and endowed with cytotoxic activity against several human carcinoma cell lines, was synthesized in three steps and with 72% overall yield from d-ribo-phytosphingosine.
The Journal of Organic Chemistry 02/2006; 71(2):836-9. · 4.45 Impact Factor
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ABSTRACT: This tutorial review surveys the use of thioglycosides in the development of sequential glycosylation methodologies, with a focus on chemoselective, orthogonal and iterative glycosylation strategies reported since the beginning of this century. Both fundamental aspects of glycosidic bond formation and ingenious state-of-the-art methodologies are presented.
Chemical Society Reviews 10/2005; 34(9):769-82. · 28.76 Impact Factor
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ABSTRACT: The chemo- and regioselective TEMPO/BAIB-mediated oxidation of 2,6- and 3,6-dihydroxy 1-thio glycopyranosides to the corresponding 1-thio uronic acid lactones is described. These locked 1-thio glycuronides can directly be used as donors in glycosidation reactions using the Ph(2)SO/Tf(2)O reagent system. Alternatively, selective opening of the lactone bridge liberates a hydroxyl function for ensuing glycosylations.
Organic Letters 06/2005; 7(10):2007-10. · 5.86 Impact Factor
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ABSTRACT: The first synthesis of the trisaccharide repeating unit of the acidic polysaccharide of the bacteriolytic complex of lysoamidase is presented. The construction is based on a linear glycosylation strategy that starts from the reducing end and employs thio- and selenoglycosides in a highly stereoselective manner by a single set of activation conditions. The thus-formed trisaccharide is selectively deprotected and oxidised, after which a final deprotection step furnishes the desired repeating unit.
Chemistry 02/2005; 11(3):1010-6. · 5.93 Impact Factor
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ABSTRACT: The synthesis of a neoglycoconjugate containing the Galili epitope trisaccharide connected to a spacer‐lipid entity is described. The α‐D‐Galp‐(1→3)‐β‐D‐Galp‐(1→4)‐β‐D‐GlcpNAc trisaccharide, equipped with a 3‐aminopropyl spacer, is efficiently assembled from easily accessible building blocks in a one‐pot procedure. Global deprotection of the trisaccharide and ensuing introduction of a bis(palmitamido)‐ propanamido moiety afforded title compound 1 as depicted in Scheme 1.
Journal of Carbohydrate Chemistry 01/2005; 24(7):755-769. · 0.63 Impact Factor
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ABSTRACT: [reaction: see text] A novel sequential glycosylation procedure is described that combines the use of 1-hydroxyl and thiodonors. The Ph(2)SO/Tf(2)O-mediated dehydrative condensation of 1-hydroxyl donors with thioglycosides affords in good yield the thiodisaccharides, which in turn can be activated by the same activator system to furnish trisaccharides. The alpha-Gal epitope and a hyaluronan trisaccharide were efficiently assembled in a one-pot procedure.
Organic Letters 06/2003; 5(11):1947-50. · 5.86 Impact Factor
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ABSTRACT: Diphenylsulfoxide in combination with triflic anhydride provides a very potent thiophilic glycosylation promotor system, capable of activating disarmed thioglycosides. The usefulness of this novel thiophilic activator is illustrated in a successful chemoselective glycosylation sequence in which the donor thioglycoside in the first condensation step may be either armed or disarmed. [reaction: see text]
Organic Letters 06/2003; 5(9):1519-22. · 5.86 Impact Factor
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ABSTRACT: A general, modular strategy for the first completely stereoselective synthesis of defined heparin oligosaccharides is described. Six monosaccharide building blocks (four differentially protected glucosamines, one glucuronic and one iduronic acid) were utilized to prepare di- and trisaccharide modules in a fully selective fashion. Installation of the alpha-glucosamine linkage was controlled by placing a conformational constraint on the uronic acid glycosyl acceptors thereby establishing a new concept for stereochemical control. Combination of disaccharide modules to form trans-uronic acid linkages was completely selective by virtue of C2 participating groups. Coupling reactions between disaccharide modules exhibited sequence dependence. While the union of many glucosamine uronic acid disaccharide modules did not meet any problems, certain sequences proved not accessible. Elaboration of glucosamine uronic acid disaccharide building blocks to trisaccharide modules by addition of either one additional glucosamine or uronic acid allowed for stereoselective access to oligosaccharides as demonstrated on the example of a hexasaccharide resembling the ATIII-binding sequence. Final deprotection and sulfation yielded the fully synthetic heparin oligosaccharides.
Chemistry 02/2003; 9(1):140-69. · 5.93 Impact Factor
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Chemistry 12/2002; 9(1):140 - 169. · 5.93 Impact Factor
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ABSTRACT: Low temperature mannosylation of glycosyl acceptors under the agency of S-(4-methoxyphenyl) benzenethiosulfinate (MPBT) and trifluoromethanesulfonic anhydride (Tf2O) with p-methoxyphenyl 2-azido-3-O-benzyl-4,6-O-benzylidene-2-deoxy-1-thio-α-d-mannopyranoside, readily available from d-mannosamine hydrochloride, affords 2-azido-2-deoxy-d-mannosides with high β-selectivity in good yields.
Tetrahedron Letters - TETRAHEDRON LETT. 01/2001; 42(49):8693-8696.
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Remy E.J.N. Litjens
