Designing of dipeptide‐based oligoconjugates as potential carrier for drug delivery. Pyroglutamil‐S‐glutamic acid bisoligo‐3‐hydroxybutyrates

In the present article, we describe the synthesis and characterization of conjugates based on pyroglutamyl‐S‐glutamic acid and bisoligo‐[R,S]‐3‐hydroxybutyrates (PyGlu‐S_‐Glu_bisOHB) using anionic ring opening polymerization of β‐butyrolactone with a dipeptide bearing two carboxylate groups as potassium salt. The results indicated that the above‐mentioned reaction is accompanied of oligomerization of β‐butyrolactone yielding (3‐hydroxybutyrates) oligomers with crotonate and carboxyl end groups. We report also the end group analysis of the synthesized conjugates using electrospray ionization tandem mass spectrometry (ESI‐MS), the latter confirmed the presence of a mixture of dipeptide conjugate with β‐butyrolactone oligomer chain and β‐butyrolactone homopolymer. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4103–4111, 2008     

The umpolung of substituent effect in nucleophilic aromatic substitution. A new approach to the synthesis of N,N-disubstituted melamines (triazine triskelions) under mild reaction conditions

By the umpolung of substituent effect 1,3,5-triazines substituted with three dialkylamino groups were prepared under mild reaction conditions by treatment of cyanuric chloride with tertiary amines. Quaternary N-triazinylammonium salts were identified as reactive intermediates activating the triazine ring and strongly promoting the persubstitution of all chlorine atoms. The final degradation of intermediate N-triazinylammonium chlorides proceeded at room temperature or in boiling dichloromethane spontaneously within irreversible evolution of appropriate chloroalkane.     

Dynamische interpretation von infrarotspektren

(Dynamic Interpretation of Infrared Spectra) Results of investigation of an algorithm, based on a novel static-dynamic method, for interpretation of infrared spectra are presented. The IRSCAN-D algorithm can recognize 103 infrared-active substructures comprising C, H, N, O, S, halogen, P and Si atoms. The results indicate that the algorithm is efficient; roughly 97% of the substructures are correctly ascribed, with a surprisingly low number (60%) of false recognition.     

Diaza crown ethers bearing heterocyclic ligating groups on nitrogen atoms and their complexing properties with divalent inorganic cations

Two nitrogen-substituted 4,13-diaza-I8-crown-6 compounds, bearing 2-methylquinolyl and 2-methylquinolyl-1-oxide groups, have been prepared. Ionophore-cation selectivities with a range of inorganic divalent cations have been investigated by means of membrane techniques, demonstrating their high selectivity for the Hg(II) cation.     

Syntheses and reactions of terpene β-hydroxyselenides and β-hydroxydiselenides

A convenient method for the synthesis of optically active trans-hydroxyselenides and trans-hydroxydiselenides from the bicyclic terpene group based on the reactions of sodium selenide or sodium diselenide with cis- and trans-(+)-3-carane, trans-(+)-2-carane and (?)-β-pinane epoxides is described. The corresponding cis-hydroxy and cis-methoxydiselenides were obtained in the reaction of sodium diselenide with β-hydroxy- and β-methoxytosylates. The influence of a hydroxy group at the β-position on the diastereomeric ratio of the products of the asymmetric methoxyselenenylation of styrene has been established by composition of the products, crystal structure analyses, and theoretical calculations using a DFT method on the B3LYP level (6-311G(d)).     

Guest Editor's Note: Clifford Algebras and Their Applications

The history and immediate future of the International Conferences on Clifford Algebras and Their Applications. Seven topical sessions in Ixtapa. Dirac operator: cross relations. Polemic guide: signature change, quasigroups, pseudotwistors. Clifford cogebra, coconnection and Dirac operator for Clifford cogebra.     

New Schiff base complexes of ruthenium(III) and their use as catalysts for O-allyl systems isomerization

Seven new ruthenium(III) complexes of the general formula [RuCl(PPh₃)LL′] · xH₂O (LL′ = [ONNO] = symmetrical and unsymmetrical Schiff base derivatives of trans-1,2-diaminocyclohexane and 2-hydroxynaphthaldehyde as well as R-salicylaldehydes, x = 0–3) have been synthesized. The complexes were characterized by physico-chemical and spectroscopic techniques. The catalytic activities of the complexes in the isomerization reaction of selected O-allyl systems, i.e., 1,4-diallyloxybutane and 4-allyloxybutan-1-ol have been studied. Some of the complexes showed high efficiency and E-stereoselectivity in double bond migration of allyl group to 1-propenyl group and high selectivity of isomerization of allyloxyalcohol to cyclic acetal.     

Decompositions of graphs into trees

Let θ be a family of graphs. By a θ-decomposition of a graph G we mean a partition λ of the edge set of G such that every F ? π spans in G a subgraph isomorphic to a graph in θ. In this paper we state the following conjecture: If T₁ and T₂ are two trees having relatively prime sizes then there exists c = c(T₁ T₂) such that every graph G satisfying the condition δ(G) ? c has a {T₁, T₂}-decom-position. We prove this conjecture for some special pairs of trees. In particular, we prove it in the following cases: (i) T₁ and T₂ are stars having relatively prime sizes; (ii) T₁ and T₂ are paths having relatively prime sizes; and. (iii) T₁ = T₂ - {v}, where v is a terminal vertex in T ₂.     

The kinetics of successive addition of oxirane to alkanethiols in the presence of basic catalysts

Rate constants and activation parameters of direct reaction of oxirane with certain alkyl-2-hydroxyethyl sulfides and/or successive oxyethylene adducts in the presence of basic catalyst were studied at temperatures 323–353 K. The reactions were found to be of the first order with respect to oxirane, sulfide, and catalyst concentrations. The kinetics are consistent with a termolecular mechanism.