Guido Zosimo-Landolfo

New types of spin-labelled sugar and nucleoside analogs: Pyrrolidine, morpholine and piperidine N-Oxyls

Abstract Analogs of blocked furanose ( 20 ) or pyranose sugars (i.e. 15 ) and of nucleosides (i.e. 23 ) in which the ring oxygen has been replaced with a -N(OH)-bridge have been prepared in generally good yields by a general reductive cyclization procedure preserving the configuration of the preexistant asymetric centers and proceedings stereoselectively (in more favorable cases stereospecifically) when creating a new asymetric center. The title compounds oxidized to nitroxide free radicals affording usable ESR spectra.

Terminal Deoxy Hydroxyamino Sugars

Abstract Reduction of sugar aldoximes gave in good yield the corresponding terminal deoxy hydroxyamino sugars. These compounds were found to be reasonably stable (they could be kept for some weeks at 4° C). On standing in the air, these compounds in solution were spontaneously oxidized to the corresponding nitroxide free radicals whose ESR spectra gave useful structural information.

Synthetic usefulness of the sugar cyclopentylidene ketals

ABSTRACT Cyclopentylidene ketals, moderately more acid-labile than their isopropylidene analogs, offer an alternative to the latter blocking groups. They have been shown to resist a large variety of reaction conditions commonly encountered in carbohydrate chemistry.

Amidoximes α-Hydroxylées Dérivées de Sucres

Abstract The two epimeric α-hydroxyamidoximes 5 and 6 - and some derivatives thereof, particularly oxadiazoles 16 and 17 - have been stereospecifically prepared from the keto sugar 1. Compound 5 was found to exist in two polymorphous crystalline forms (α and β) depending on the crystallization solvent. Both forms are orthorhombic, space group P212121 (α-form : a = 10.408(3), b = 10.559(2), c = 14.144(2) A; β-form : a = 7.890(1), b = 10.305(2), c = 19.064(4) A). The calculation of pseudorotation parameters showed that each polymorph is associated with a slightly different conformation of the dioxolane rings. The Oacetyl derivative 11 of 6 adopts a different conformation of the furanose ring. In the three structures, a network of hydrogen bonds exists. The amidoxime 5 forms a cupric complex [Cu(5)2] whose ESR spectrum proved its square structure.

New α-chloralose derivatives

Chloralose is an easily available carbohydrate derivative bearing biological properties. It constitutes a convenient starting material for various synthetic developments. Herein we describe the preparation of hydroxylamino derivatives of α-chloralose using well-established synthetic procedures.

Spacer arms bearing two N-hydroxyimino groups and nitroxyl free radicals thereof

Synthesis and e.s.r. study of model compounds in which two blocked sugar units are connected by a spacer arm that includes two N-hydroxyimino groups, with the aim of testing the feasibility of generating diradical species from such precursors

Communication: Blocked Disaccharide Analogs Bearing an Oxyimino Interglycosidic Bridge

Oligosaccharide units in which a ONH group replaces the usual oxy bridge have been encountered in nature, for ex. in the antitumor antibiotic calicheamicin γ1,2 and the biological importance of this peculiar interglycosidic junction has been emphasized.3 The N-O bond is very different from the bonds habitually found in carbohydrate chemistry, owing, in particular, to its weakness and the presence of lone-pairs on its two hetero atoms. These characteristics considerably affect the conformational properties of molecules like calicheamicin. As we have developed,4 in the CHARMm force field,5 parameters pertaining to this bond, we needed models of disaccharides of this type to fit computed results in with experimental data. These O-N-disaccharide derivatives were easily obtained from the O-aminosugar derivative 1.6

Spin Labelled C-Glycoside Analogs: Derivatives of 1,4-Anhydro-4-deoxy-2,3-O-cyclopentylidene-l,4-N-hydroxyimino-DL-erythrofuranose

A series of 2,3-O-cyclopentylidene C-glycoside analogs in which the furanose ring has been replaced with a N-hydroxypyrrolidine have been prepared. A structural study of these tricyclic compounds and the aminoxyl radicals thereof has been carried out using variable temperature 1H NMR, X-ray diffraction, molecular dynamics and EPR spectroscopy. Both types of compounds, N-hydroxypyrrolidines and pyrrolidine N-oxyls, fundamentally prefer - in solutions- N-endo conformations over the alternate, N-exo forms found by X-ray diffraction studies and computed to be more stable by molecular dynamics.

Hydroxyamino sugar derivatives: sugar nitrones

We describe in this paper the preparation of 46 new sugar nitrone derivatives and their antibacterial activity against Escherichia coli and Bacillus subtilis.

NOTIZEN: Hydroxyamino Sugar Derivatives: New Glycolipid Analogs

Synthetic glycolipid analogs are very useful as nonionic detergents for solubilization of membrane proteins [1]. Although a large number of such detergents were described, very few ones fully satisfy the desirable properties needed for such compounds [2].