Alpha-glucosidase inhibitory and antioxidant acridone alkaloids from the stem bark of Oriciopsis glaberrima ENGL. (Rutaceae)

The CH2Cl2/MeOH extract of the stem bark of Oriciopsis glaberrima ENGL. afforded four new acridone alkaloids namely oriciacridone C, D, E and F along with six known compounds: atalaphyllidine, oleanolic acid, butulinic acid, beta-sitosterol, stigmasterol, glucoside of stigmasterol and one synthetically known acridone: 1,3,5-trihydroxy-4-prenylacridone. The structures were established on the basis of MS, 1D and 2D NMR experiments. The acridones 1, 4 and 5 showed potent activity against alpha-glucosidase, while the acridones 1-5 showed moderate free radical scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH).     

Solvolysis–hydrolysis of N-bearing alkoxysilanes: Reactions studied with 29Si NMR

The hydrolysis reactions of 8 different N-bearing alkoxy-silane coupling agents, namely: 3-cyanopropyl triethoxy silane (CPES), triethoxy-3-(2-imidazolin-1-yl) propyl silane (IZPES), and amino silanes, 3-aminopropyl triethoxy silane (APES), 3-aminopropyl trimethoxy silane (APMS), 3-(2-aminoethylamino)propyl trimethoxysilane (DAMS), 3-[2-(2-aminoethylamino)ethylamino] propyl trimethoxysilane (TAMS), 4-amino-3,3-dibutyl trimethoxy silane (ADBMS) and trimethoxy [3-(phenylamino)propyl] silane (PAPMS) were carried out in ethanol/water 80/20 (w/w) solutions in acidic media and followed in situ by ¹H-, ¹³C- and ²⁹Si-NMR spectroscopy. Acidic conditions were selected in order to enhance the formation of silanol and to slow down the self condensation reactions of the hydrolyzed functions. ²⁹Si NMR spectroscopy revealed the formation of intermediate species, particularly the solvolysis of γ-amino silanes by reaction exchange with the alcoholic solvent.     

The shortest multipaths problem in a capacitated dense channel

In this paper, we present a simple polynomial-time algorithm solving the shortest multipaths problem in particular grid graphs called dense channels. Our work extends the results of Formann et al. [M. Formann, D. Wagner, F. Wagner, Routing through a dense channel with minimum total wire length, Journal of Algorithms 15 (1993) 267–283], by considering arbitrary horizontal and vertical capacities.     

Synthesis and evaluation of P-chirogenic monodentate binaphthyl phosphines

P-Chirogenic monodentate binaphthyl phosphines were prepared in five steps from enantiomerically pure BINOL. This approach supposes the utilization of two methods previously developed in our group, the formation of secondary phosphine oxide, and the reduction of tertiary phosphine oxide using the association of tetramethyldisiloxane and Ti(OⁱPr)₄. During the last reduction step, only the formation of the more stable diastereoisomer was observed. This product was employed as a ligand for the palladium catalyzed hydrosilylation of styrene to afford the corresponding alcohol with high yield and enantiomeric excess.     

Reversed-phase high-performance liquid chromatography of nucleoside analogues. Simultaneous analysis of anomeric D-xylo- and D-lyxofuranonucleosides and some other D-pentofuranonucleosides

Reversed-phase high-performance liquid chromatography using a C18 column was applied to the analysis of reconstituted mixtures of previously synthesized alpha, beta D-xylo- and D-lyxofuranonucleosides as well as a number of commercially available D-ribo- and D-arabinofuranonucleosides. From a detailed study of various parameters (size of support particles, nature and pH of the mobile phase, temperature), optimized conditions were established. Correlations between the retention times and structures of the bases, the orientations of the secondary hydroxyl groups of the sugar moiety and the anomeric configurations of the nucleosides are also reported.     

Synthesis of 4-azacyclopent-2-enones and 5,5-dialkyl-4-azacyclopent-2-enones

Three different methods are reported for the preparation of 4-azacyclo-2-enones 1, two of which allow the preparation of the compounds in optically active form. In addition, a facile route to 4-aza-5,5-dimethylcyclopent-2-enones 2 is disclosed.     

Synthesis of macrolide-saccharide hybrids by ring-closing metathesis of precursors derived from glycitols and benzoic acids

The benzomacrolactone structural motif is a privileged or evolutionarily selected scaffold that codes properties required for binding to proteins and novel analogues thereof may provide a source of new bioactive compounds. Saccharides are also privileged structures, with (amino)sugars, iminosugars, and sugar amino acids being applied as scaffolds for the development of nonpeptidal peptidomimetics. The syntheses of novel polyhydroxylated oxamacrolides, structural analogues of natural polyketide derived macrolides, are described herein, providing a basis for their development as scaffolds. The syntheses were carried out from benzoic acids and appropriately protected D-mannitol or D-sorbitol (D-glucitol). Ring-closing metathesis was applied in the macrocyclization step with high E-alkene selectivities being observed. X-ray crystal structures, for two polyhydroxylated derivatives, show that the macrocyclic rings display similar conformations. In addition, intermolecular hydrogen-bonding networks are observed in the lattices.     

Complexation of lanthanum(III) nitrate by N,N′,N,N′-tetraethylmalonamide: Crystal structure of three polymorphic forms

A monoclinic form of the complex between lanthanum(III) nitrate and tetraethylmalonamide (TEMA), La(NO₃)₃(TEMA)₂, 1, differing from the triclinic form 2 previously reported, is described. 1 undergoes an evolution with time which leads to the form 2, which in its turn undergoes a temperature-driven phase transition previously unreported, leading to the formation of 3.