C. A. A. Van Boeckel

Synthesis of a Pentasaccharide Corresponding to the Antithrombin III Binding Fragment of Heparin

Abstract The synthesis of a protected pentasaccharide 27b corresponding to the antithrombin III binding region of heparin is presented. This pentasaccharide was prepared from two disaccharides (12c and 23) and a monosaccharide (1). The glucuronic acid containing disaccharide 12c was prepared from easily available monomers 6 and 7. Oxidation to the uronic acid was performed in the disaccharide stage. L-Idose derivative 16, prepared via a new route, was coupled with 1,6-anhydro derivative 17, oxidized and transformed into disaccharide 23. Coupling of 12c and 23 to tetrasaccharide 24a has been investigated. Better yields were obtained without collidine, the reason for which is explained. Coupling of 24b and 1 afforded the pentasaccharide 27b, protected with acetyl at the positions to be sulphated, benzyl at the other hydroxyl functions and azide at the 2-position of the glucosamine residues. Conversion of 27b into the sulphated pentasaccharide Ib can be performed according to published procedures.

A new approach to the synthesis of phosphotriester intermediates of nucleosides and nucleic acids

Abstract Aryl phosphorodichloridates can be converted by means of 1-hydroxybenzotriazole into an effective phosphorylating agent, which can be applied to the synthesis of phosphotriester intermediates of nucleic acids.

Substituent effects on carbohydrate coupling reactions promoted by insoluble silver salts

Abstract Coupling reactions were performed in the α-D-glucopyranosyl bromide series (i.e. compounds 1 a–c, 2 a, b, 3 and 4 ) and the α-D-mannopyranosyl bromide series (i.e. compounds 7 a–c, 8 a, b, 9 ) with aglycons 5 or 10 in the presence of insoluble silver salt promotors. (i.e. silver silicate and silver zeolite). The insoluble silver salt promotes the formation of the β-glycosidic linkage, while a non-participating group is present at C-2 of the glycon. It was found that in both series 4-O-acyl functions increase the β/α ratio of the glycosidic bond formation relative to 4-O-alkyl functions, whereas 3-O and 6-O-acyl functions decrease this ratio. We assume that inductive effects are responsible for the influence exerted by 3-O-substituents, but that through-bond interactions are essential for the effects exerted by 4-O and 6-O substituents. Another unexpected finding was that coupling of α-D-mannopyranosyl bromide derivatives gave much higher β/α ratios than the corresponding reactions of α -D-glucopyranosyl bromides.

Hydrazinedithiocarbonate (HDTC) as a new reagent for the improved removal of chloroacetyl and bromoacetyl protective groups.

Abstract The use of hydrazinedithiocarbonate (HDTC) for the removal of chloroacetyl and bromoacetyl groups is described. The advantage of this reagent is the selective deprotection under mild conditions, which was demonstrated on carbohydrate derivatives.

The First Orally Active Low Molecular Weight Agonists for the LH Receptor: Thienopyr(im)idines with Therapeutic Potential for Ovulation Induction

The gonadotropins, a class of glycoproteins with an average molecular weight of 30 kD, play a pivotal role in human reproduction. Follicle stimulating hormone (FSH), for example, causes ovarian follicle maturation in women and is involved in spermatogenesis in men. Luteinizing hormone (LH) is responsible for ovulation induction in women and controls testosterone production in men. Finally, human choriogonadotropin (hCG) maintains the early stages of a pregnancy. All gonadotropins consist of a common subunit and a hormone-specific Support from the Forschungsinstitut f ̧r Molekulare Pharmakologie is gratefully acknowledged. M.S. was supported by the DFG Graduiertenkolleg GRK 80 TMModellstudien∫. The authors thank Wolfgang Bermel for helpful discussions regarding the setup of the TROSY experiments, Hartmut Oschkinat for his continuous encouragement, and Karen Zierler for carefully reading the manuscript.

A review of the methods of chemical synthesis of sulphate and glucuronide conjugates

1. Methods for the synthesis of drug conjugates with sulphuric acid have been reviewed. 2. Some analytical methods are presented for the analysis of sulphate conjugates. 3. The synthesis of several types of N, O and C beta-D-glucuronides is reviewed. Different beta-coupling reactions of protected glucuronides are presented. 4. Application of n.m.r. and mass spectrometry to the analysis of beta-D-glucuronides is discussed.

Fluorescence Assays for High-Throughput Screening of Protein Kinases

Protein kinases comprise one of the most important group of targets for drug discovery research today. Methods to identify novel kinase inhibitors by high-throughput screening have evolved rapidly in recent years. An important aspect is the availability of fluorescent probes that can be applied in a homogeneous, or mix-and-measure, assay format. Here, we illustrate the application of fluorescence read-out technologies for kinase targets in light of our own experiences in assay development and high-throughput screening.

Syntheses of heparin-like pentamers containing opened uronic acid moieties

Abstract The syntheses of four analogues of pentasaccharide Ia , which corresponds to the minimal AT III binding region of heparin, are presented and the biological activities of these analogues will be discussed. Three of these analogues (i.e. compounds II , III and IV ) contain an R -glyceric acid oxymethylene residue ( i.e. B in fig.3 ) instead of α-L-iduronic acid and in the other analogue ( i.e. compound V ) the β-D-glucuronic acid unit has been replaced by an s -glyceric acid oxymethylene residue ( i.e. A in fig3 ). The R and S -glyceric acid oxymethylene residues represent an “opened” iduronic acid unit and an “opened” glucuronic acid unit, respectively, containing the essential carboxylate function in the appropriate configuration. The crucial step in the syntheses of these “opened” uronic acid pentamer analogues, was the preparation of the required glyceric acid oxymethylene residues 8a , 8b and 8c . Analogues II and III , containing an “opened” iduronic acid moiety, display a significant AT III mediated αXa activity. Compound III contains two extra sulphate groups at unit 2 . Removal of the contributing O-sulphate groups at position 3 and 6 of unit 6 of compound II ( i.e. compound IV ) results in a seven-fold drop in αXa activity. Replacement of the β-D-glucuronic acid unit by an S -glyceric acid oxymethylene residue ( i.e. compound V ) leads to almost a complete loss of αXa activity, notwithstanding the fact that all the essential and contributing charged groups are present in the molecule.

Synthesis of a potent antithrombin activating pentasaccharide: A new heparin-like fragment containing two 3-O-sulphated glucosamines

Abstract The synthesis of a pentasaccharide corresponding to the antithrombin III binding region of herapin, but containing an extra 3-O-sulphate group at the reducing end, is described. This compound elicits higher anti-Xa activity than the antithrombin III binding region of heparin.

1-aminoisoquinoline as benzamidine isoster in the design and synthesis of orally active thrombin inhibitors

Replacement of the highly basic benzamidine moiety of NAPAP by the moderately basic 1-aminoisoquinoline moiety resulted in thrombin inhibitors with improved selectivity towards trypsin and enhanced Caco-2 cell permeability.