STABILITY NUMBER IN SUBCLASSES OF P5-FREE GRAPHS

Two new hereditary classes of P5-free graphs where the stability number can be found in polynomial time are proposed. They generalize several known results.     

Synthesis of Phosphocapped Derivatives of β-Cyclodextrin

Russian Journal of General Chemistry -     

Poly(phosphoramidites)-Polycondensation Products of Phosphorous Triamides with Aliphatic Diols and Dibasic Phenols

Phosphorous triamides react with aliphatic diols and dibasic phenols: 1,6-hexanediol, 2,2'-(4-hydroxyphenyl)propane, 1,4-hydroquinone, and 4,4'-dihydroxybiphenyl in the temperature range 80-110°C in diethylene glycol dimethyl ether or without a solvent to afford phosphorus-containing regular high-molecular products having an O₂P(NR₂) moiety in the monomeric unit. The resulting poly(phosphoramidites) are capable of swelling in organic solvents, and they can be used as macroligands in the catalytic hydrogenation of styrene over rhodium(I) complexes.     

Phosphorylation of Tetrahydric Phenols with Trivalent Phosphorus Compounds. Synthesis of Tetraphosphites

The reactions of 1,1'-spirobi(5,6-dihydroxy-3,3-dimethylindane) and 1,2,4,5-tetrahydroxybenzene with 2-chloro-1,2,3-dioxaphosphorinanes of various structure were used to obtain tetraphosphorylated systems. Investigation of the chemical properties of the products was initiated. Basing on 1,1'-spirobi(3,3-dimethylindane-5,6-diyl) tetra(2,2-dimethylpropanediyl phosphite), a Pt(II) chelate was synthesized.     

Di‐ and triphenylacetate complexes of yttrium and europium

The significant variety in the crystal structures of rare‐earth carboxylate complexes is due to both the large coordination numbers of the rare‐earth cations and the ability of the carboxylate anions to form several types of bridges between rare‐earth metal atoms. Therefore, these complexes are represented by mono‐, di‐ and polynuclear complexes, and by coordination polymers. The interaction of LnCl₃(thf)_x (Ln = Eu or Y; thf is tetrahydrofuran) with sodium or diethylammonium diphenylacetate in methanol followed by recrystallization from a DME/THF/hexane solvent mixture (DME is 1,2‐dimethoxyethane) leads to crystals of the non‐isomorphic dinuclear complexes tetrakis(μ‐2,2‐diphenylacetato)‐κ⁴O:O′;κ³O,O′:O′;κ³O:O,O′‐bis[(1,2‐dimethoxyethane‐κ²O,O′)(2,2‐diphenylacetato‐κ²O,O′)europium(III)], [Eu(C₁₄H₁₁O₂)₆(C₄H₁₀O₂)₂], (I), and tetrakis(μ‐2,2‐diphenylacetato)‐κ⁴O:O′;κ³O,O′:O′;κ³O:O,O′‐bis[(1,2‐dimethoxyethane‐κ²O,O′)(2,2‐diphenylacetato‐κ²O,O′)yttrium(III)], [Y(C₁₄H₁₁O₂)₆(C₄H₁₀O₂)₂], (II), possessing monoclinic (P2₁/c) symmetry. The [Ln(Ph₂CHCOO)₃(dme)]₂ molecule (Ln = Eu or Y) lies on an inversion centre and exhibits three different coordination modes of the diphenylacetate ligands, namely bidentate κ²O,O′‐terminal, bidentate μ₂‐κ¹O:κ¹O′‐bridging and tridentate μ₂‐κ¹O:κ²O,O′‐semibridging. The terminal and bridging ligands in (I) are disordered over two positions, with an occupancy ratio of 0.806 (2):0.194 (2). The interaction of EuCl₃(thf)₂ with Na[Ph₃CCOO] in methanol followed by crystallization from hot methanol produces crystals of tetrakis(methanol‐κO)tris(2,2,2‐triphenylacetato)‐κ⁴O:O′;κO‐europium(III) methanol disolvate, [Eu(C₁₉H₁₅O₂)₃(CH₃OH)₄]·2CH₃OH, (III)·2MeOH, with triclinic (P) symmetry. The molecule of (III) contains two O,O′‐bidentate and one O‐monodentate terminal triphenylacetate ligand. (III)·2MeOH possesses one intramolecular and four intermolecular hydrogen bonds, forming a [(III)·2MeOH]₂ dimer with two bridging methanol molecules.     

Selectin Receptors 4: Synthesis of Tetrasaccharides Sialyl Lewis A and Sialyl Lewis X Containing A Spacer Group1,2

ABSTRACT

Synthesis of two isomeric tetrasaccharides, namely Neu5Acα(2→3)Galβ(1→3)[Fucα(1→4)GlcNAcβ (sLe^a) and Neu5Acα(2→3)Galβ(1→4)[Fucα(1→3)]GlcNAcβ (sLe^x) as 3-aminopropyl glycosides is described. Preparation of these compounds was performed by sialylation of selectively protected trisaccharides Le^a and Le^x which contain three unsubstituted OH groups at positions 2, 3 and 4 of Gal residue. Glycosylation of Le^x trisaccharide with ethylthio sialoside under promotion by NIS and TfOH in acetonitrile was effective and regio- and stereoselective to give sLe^x derivative in 81% yield. In contrast, sialylation of the Lc^a acceptor was accompanied by a variety of undesirable by-processes, namely. N-thioethylation of the GlcNAc residue, β-sialylation, and lactonisation. In order to improve the yield of sLc^a tetrasaccharide the glycosylation of Le^a acceptor by sialyl donors of ethyl and phenyl thioglycoside (promoted by NIS-TfOH or NBS-Bu₄NBr), xanthate (promotion by NIS-TfOH mixture or MeOTf) and phosphite (promoted by TMSOTf) types was also studied. Among the reactions investigated the glycosylation by phenyl thioglycoside sialoside promoted by NIS-TfOH gives the best yield (39%) of sLe^a tetrasaccharide product.     

Gargano,Lewinter and Malerba问题的解

§1　IntroductionLet G be a graph with vertex-set V(G) ={ v1 ,v2 ,...,vn} .A labeling of G is a bijectionL:V(G)→{ 1,2 ,...,n} ,where L (vi) is the label of a vertex vi.A labeled graph is anordered pair (G,L) consisting of a graph G and its labeling L.Definition1.An increasing nonconsecutive path in a labeled graph(G,L) is a path(u1 ,u2 ,...,uk) in G such thatL(ui) + 1相似文献   

Synthesis of phosphorylated pyrazolones

Methods are proposed for the synthesis of phosphorylated pyrazolones by condensation of phosphonates of -keto(formyl) esters with hydrazine and its derivatives. The IR spectra are presented, and the fine structures of the compounds are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 513–516, April, 1977.