On the influence of heat transport on low- frequency paramagnetic spin-Lattice relaxation experiments

In low-frequency relaxation experiments on paramagnetic crystals, placed in liquid helium, often dispersion- and absorption curves are found, strongly deviating from those following from the thermodynamic theory of Casimir and Du Pré. For the relaxation time τabs, related to the maximum in the absorption curve, a temperature dependence τabs αT-α with 1 < α < 6 has been found frequently, accompanied sometimes with a jump at the helium-transition temperature Tλ. We computed, starting from a model including the heat conduction of lattice and helium bath and a heat resistance from crystal to bath, dispersion- and absorption curves and found that, assuming the direct process for the spin—lattice relaxation, τabs(T) (related to the maximum of the calculated absorption curve) can be described roughly as mentioned above with a jump at Tγ

Moleculen en dromen

Bio-Organische synthes

Developments in the synthesis of mycobacterial phenolic glycolipids

The highly lipophilic outer barrier of mycobacteria, such as M. tuberculosis and M. leprae, is key to their virulence and intrinsic antibiotic resistance. Various components of this mycomembrane interact with the host immune system but many of these interactions remain ill-understood. This review covers several chemical syntheses of one of these components, mycobacterial phenolic glycolipids (PGLs), and outlines the interaction of these PGLs with the human immune system, as established using these well-defined pure compounds.Bio-organic Synthesi

Protecting Group Strategies in Carbohydrate Chemistry

Carbohydrates are the most densely functionalized class of biopolymers in nature. This chapter describes the differences in the reactivity of the various functional groups on a carbohydrate ring and how to exploit these in the design of effective protecting group strategies. It then describes how protecting group effects can be used to control stereoselective transformations and reactivity‐controlled one‐pot synthesis strategies. The chapter highlights applications and strategies in automated synthesis. Different strategies have been developed to automate oligosaccharide assembly based on either solution‐phase synthesis or solid‐phase techniques, and automated solid‐phase synthesizers are now commercially available. Protecting group chemistry can make or break any (oligo)saccharide synthesis effort. The impact of protecting groups on the stereochemical outcome of a glycosylation reaction is best illustrated by the anchimeric assistance that neighboring groups can provide during a glycosylation reaction.Bio-organic Synthesi

Teichoic Acids: Synthesis and Applications

Bio-organic Synthesi

Mapping the Relationship between Glycosyl Acceptor Reactivity and Glycosylation Stereoselectivity

Bio-organic Synthesi

Doxorubicin and aclarubicin: shuffling anthracycline glycans for improved anticancer agents

Anthracycline anticancer drugs doxorubicin and aclarubicin have been used in the clinic for several decades to treat various cancers. Although closely related structures, their molecular mode of action diverges, which is reflected in their biological activity profile. For a better understanding of the structure-function relationship of these drugs, we synthesized ten doxorubicin/aclarubicin hybrids varying in three distinct features: aglycon, glycan, and amine substitution pattern. We continued to evaluate their capacity to induce DNA breaks, histone eviction, and relocated topoisomerase II alpha in living cells. Furthermore, we assessed their cytotoxicity in various human tumor cell lines. Our findings underscore that histone eviction alone, rather than DNA breaks, contributes strongly to the overall cytotoxicity of anthracyclines, and structures containing N,N-dimethylamine at the reducing sugar prove that are more cytotoxic than their nonmethylated counterparts. This structural information will support further development of novel anthracycline variants with improved anticancer activity.Bio-organic Synthesi

An orthogonally protected cyclitol for the construction of nigerose- and dextran-mimetic cyclophellitols

Cyclophellitols are potent inhibitors of exo- and endoglycosidases. Efficient synthetic methodologies are needed to fully capitalize on this intriguing class of mechanism-based enzyme deactivators. We report the synthesis of an orthogonally protected cyclitol from d-glucal (19% yield over 12 steps) and its use in the synthesis of α-(1,3)-linked di- and trisaccharide dextran mimetics. These new glycomimetics may find use as Dextranase inhibitors, and the developed chemistries in widening the palette of glycoprocessing enzyme-targeting glycomimetics.ERC-CoG-726072 “GLYCONTROL”; ERC-2020-SyG-951231 “CARBOCENTRE”Bio-organic Synthesi

Reagent controlled glycosylations for the assembly of well-defined Pel oligosaccharides

A new additive, methyl(phenyl)formamide (MPF), is introduced for the glycosylation of 2-azido-2-deoxyglucose building blocks. A linear α-(1,4)-glucosamine tetrasaccharide was assembled to prove the utility of MPF. Next, a hexasaccharide fragment of the Pseudomonas aeruginosa exopolysaccharide Pel was assembled using a [2+2+2] strategy modulated by MPF. The used [galactosazide-α-(1,4)-glucosazide] disaccharide building blocks were synthesized using a 4,6-O-DTBS protected galactosyl azide donor.Bio-organic Synthesi

On the synthesis of oligonucleotides interconnected through pyrophosphate linkages

Bio-organic Synthesi