Flexible access to conformationally-locked bicyclic morpholines

A preparatively accessible route to a series of conformationally-locked bicyclic morpholines has been developed. This flexible approach allows for diversification in order for a small array of lead-like scaffolds to be synthesised from readily available key building blocks

2 Triterpenoid Saponins From Heinsia-crinata

Two new triterpenoid saponins isolated from the root bark of Heinsia crinata were characterized as heinsiagenin A-3 beta-O-(beta-D-glucopyranosyl-(1 --> 2)-beta-D-glucopyranosyl-(1 --> 6)-[alpha-L-rhamnopyranosyl-(1 --> 2)]-beta-D-glucopyranosyl-(1 --> 2)-beta-D-glucopyranoside) and heinsiagenin A-3 beta-O-(alpha-L-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranosyl(1 --> 2)-beta-D-glucopyranoside). The structures were deduced mainly from a combination of 1- and 2D NMR experiments

Palladium catalyzed synthesis of Ca2+ indicators with aryl bithiophene and terthiophene fluorophores

Five new fluorescent indicators for Ca2+ were synthesized using the Stille reaction. They all consist of the tricarboxylate chelator APTRA (o-aminophenol-N,N,O-triacetic acid) linked to a (substituted) bithiophene or terthiophene fluorophore. The dissociation constants Kd measured via fluorimetric titrations at 21°C in 100 mM KCl buffered solution, pH 7.05, for the Ca2+ complexes with the new probes are in the range between 10 and 40 µM. © 2005 Elsevier Ltd. All rights reserved.IDO/00/001 G.0320.00N.A. wishes to thank Professor Dr. S. Icli for his support. A.K. and S.S.S. are grateful to the DWTC (Belgium) for a postdoctoral fellowship. The authors are grateful to the University Research Fund of the K.U. Leuven for IDO-grant IDO/00/001 and to the FWO for grant G.0320.00. The DWTC through IAP-V-03 is thanked for continuing support. -

a-L-fucosidases: Exoglycosidases with unusual transglycosylation properties

Copyright © 2004 American Chemical Societyα-l-Fucosidases (EC 3.2.1.51), the only members of the CAZy family GH-29, are widespread glycosidases involved in many biological processes including inflammation, metastasis, and the lysosomal storage disease fucosidosis. Despite their biological significance, information concerning the mechanism of α-l-fucosidases has only recently become available. In an attempt to obtain further data concerning their mechanism, we have investigated the hydrolytic and transglycosylation properties of a canine and a mollusk (Pecten maximus) α-l-fucosidase. Our results show that, despite the evolutionary distance between these two species, both enzymes have similar hydrolysis and transglycosylation properties. Surprisingly, we found that, starting from monosaccharides, these exoglycosidases were able to catalyze efficiently the synthesis of highly branched fuco-oligosaccharides as large as tetrasaccharides, a unique feature for a wild-type exoglycosidase. The structural analysis of the compounds formed revealed that the regioselectivity of α-l-fucosidases is strongly influenced by the structure of the acceptor. This leads us to propose an enzymatic approach for the preparative synthesis of fuco-oligosaccharides. This will not only allow the synthesis of biological determinants containing fucose but also of new fucose-containing oligosaccharides as α-glycosynthases appear to be difficult to obtain.Olivier Berteau, Julie Bielicki, Amuri Kilonda, Delphine Machy, Donald S. Anson, and Lennart Kenn