Effects of Structural Factors in Silyl Ethers Derived from Terminal Acetylenic Alcohols on 1,4-O→Csp Migration of the Silyl Group

Effects of structural factors in silyl ethers derived from terminal acetylenic alcohols on 1,4-OC_sp migration of the silyl group in the Iotsitch reagent were studied. The effect of steric factor at the carbon atom neighboring to the reaction center was found to be stronger than that at the silicon atom in the migrating group.     

8,8′-Bis(diphenylphosphinomethyl)-1,1′-binaphthyl. Synthese und Konformation

Summary The title compound3 was prepared from 8,8-Bis(bromomethyl)-1,1-binaphthyl (1) in two steps in approx. 10% overall yield. The crystal structure of the intermediate phosphinoxide2 was determined. Attempts to prepare chelate complexes of3 with Ni(II) or Pd(II) failed.

     

Synthesis of O-α-L-Fucopyranosyl-(1→2)-O-β-D-galactopyranosyl-(1→4)-2-acetamido-2-deoxy-D-glucopyranose. The H-Blood Group Specific Trisaccharide

Abstract

Different reaction conditions were investigated for the preparation of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranoside (5). Compound 5 on reaction with 2,3,4,6-tetra-O-acetyl-α-D-galactopyranosyl bromide afforded the 4-O-substituted 2-acetamido-2-deoxy-β-D-glucopyranosyl derivative which, on O-deacetylation, gave benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-4-O-β-D-galactopyranosyl-β-D-glucopyranoside (8). The trimethylsilyl (Me₃Si) derivative of 8, on treatment with pyridineacetic anhydride-acetic acid for 2 days, gave the disaccharide derivative having an O-acetyl group selectively introduced at the primary position and Me₃Si groups at the secondary positions. The latter groups were readily cleaved by treatment with aqueous acetic acid in methanol to afford benzyl 2-acetamido-4-O-(6-O-acetyl-β-D-galactopyranosyl)-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranoside, which on isopropylidenation gave the desired, key intermediate benzyl 2-acetamido-4-O-(6-O-acetyl-3,4-O-isopropylidene-β-D-galactopyranosyl)-3,6-di-O-benzyl-2-deoxy-β-D-glucopyranoside (12). Reaction of 12 with 2,3,4-tri-O-benzyl-α-L-fucopyranosyl bromide under catalysis by bromide ion afforded the trisaccharlde derivative from which the title trisaccharide was obtained by systematic removal of the protective groups. The structures of the final trisaccharide and of various intermediates were established by ¹H and ¹³C NMR spectroscopy.     

Clusters and Aggregates of 1,1′-Bis(diphenylphosphino)ferrocene (dppf)

The emerging interest of ferrocenyl diphosphines in metal complexes has led to some significant developments recently in the clusters, polymetallic aggregates and oligomers of 1,1-bis(diphenylphosphino)ferrocene (dppf). In this review, we shall focus on the synthetic strategies and the chemical, structural and bonding characteristics of these materials.     

Reaction of 2-Alkoxypropenals with α-Hydroxyamino Oximes and 1,2-Bis(hydroxyamino)cyclohexane

Reactions of 2-alkoxypropenals with α-hydroxyamino oximes in neutral medium involve the aldehyde group of the former to afford both acyclic and cyclic azomethine oxides: N-(2-hydroxyiminoalkyl)-N-(2-alkoxy-2-propenylidene)amine oxides and 1-hydroxy-2,5-dihydroimidazole 3-oxides. The state of tautomeric equilibrium between the cyclic and acyclic products depends on the solvent nature and temperature. The reaction in acidic aqueous medium is accompanied by hydrolysis of the vinyl ether moiety in 2-alkoxy-propenals with formation of 2-oxopropionaldehyde which reacts with α-hydroxyamino oxime at the hydroxy-amino group to give substituted pyrazine 1,4-dioxides. The reaction of 2-alkoxypropenals with 1,2-bis-(hydroxyamino)cyclohexane leads to formation of 2-(1-alkoxyvinyl)-1,3-dihydroxyperhydrobenzimidazoles. The structure of the products was proved by IR, UV, and ¹H and ¹³C NMR spectroscopy and X-ray analysis.     

Dithiocarbamate Complexes of Nickel(II) with 1,1′-Bis(Diphenylphosphino) Ferrocene

Ni(II) complexes of composition [Ni(bzⁱprdtc)(dppf)]X, [Ni(but₂dtc)(dppf)]X and [Ni(Rdtc)(dppf)]X [bz = C₇H₇; ⁱpr = C₃H₇; but = C₄H₉; R = pld = C₄H₈; tz = C₃H₆S; hmi = C₆H₁₂; dtc = S₂CN; dppf = 1,1'-bis(diphenylphosphino)ferrocene C₃₄H₂₈P₂Fe; X = ClO₄, I, Br, NCS] were synthesized and characterized X-ray structural analysis of [Ni(hmidtc)(dppf)]ClO₄ confirmed coordination number four for nickel in a distorted, square-planar, NiS₂P₂ arrangement     

Formation of (±)-1,2-O-Ethylidene-myo-Inositol During the Reaction Between Triethyl Orthoformate and myo-Inositol in DMSO

Besides myo-inositol monoorthoformate (1), (±)-1,2-O-ethylidene-myo-inositol (2) was obtained as another product in the reaction between triethyl orthoformate and myo-inositol in DMSO catalyzed by acid under N₂     

Formation of the phase structure of polymer systems of ethylene copolymers–[3-(2-aminoethylamino)propyl]trimethoxysilane

Solubility of components is investigated in a wide range of temperatures and formulations in systems of ethylene copolymers–[3-(2-aminoethylamino)propyl]trimethoxysilane. Phase diagrams are constructed. Temperature and concentration ranges of variation of solubility are revealed, and the structure of modified copolymers is studied.     

Polymerization of Styrene in Supercritical CO_2-swollenPoly(ethylene terephthlate)

Supercriticalfluids(SCFs)havemanyfeatures,suchashighcompressibility,highdiffusivityandlowviscosity,whichmakethemattractiveformanyindustrialprocesses.supercritical(sc)co=isthemostpopularbecauseitisnon-toxic,non-nammable,andeasytoobtainandhasanear-ambientcriticaltemperature.SCCO=canswellglassypolymers'.AdditivesintheSCCO,candiffuseintotheswollenpolymerandtheCO=canberemovedcompletelyondepressurization,leavingmostadditivesinthepolymer.Thussolvent-freeimpregnationofadditivescanbeachieved.Ifadd…     

Synthesis of O-(2-Acetamido-2-Deoxy-β-D-Glucopyranosyl)-(l→2)-O-α-D-Mannopyranosyl-(l→6)-O-β-D-Glucopyranosyl-(1→4)-2-Acetamido-2-Deoxy-D-Glucopyranose. A Potential Acceptor-Substrate for N-Acetylglucosaminyltransferase-V (GnT-V)

Abstract

The reaction of phenyl 3,4,6-tri-O-acetyl-2-deoxy-2-phthaIimido-l-thio-β-D-glucopyranoside with methyl 3,4,6-tri-O-benzyl-α-D-mannopyranoside catalysed by iodonium ion (TfOH-NIS) followed by deacylation-acetylarion afforded disaccharide 11. which was readily converted (in four steps) to bromide 12. A similar glycosylarion with phenyl 2,3,4,6-tetra-O-acetyl-l-thio-D-glucopyranoside of benzyl 2-acetamido-3,6-di-O-benzyl-2-deoxy-α-D-glucopyranoside 16 followed by O-deacetylation of the resulting intermediate gave disaccharide 18. The 4,6-O-benzylidene derivative of 18 was acetylated then deacetaled to give diol 21. This diol acceptor was condensed with bromide 12 (promoted by mercuric cyanide) to give the partially protected tetrasaccharide derivative 22 which was O-deacetylated and then subjected to catalytic hydrogenation to furnish the title tetrasaccharide 6. The structure assigned to 6 was supported by ¹H and ¹³C NMR spectral data and FAB mass spectroscopy.     

Mukaiyama Aldol Reaction of 1,2-Bis(trimethylsiloxy) Cyclobutene Catalyzed by Magnesium(II) Iodide

Theuniquereactivityof1,2-bis(trimethylsiloxy)cyclobutene(BTCB)towardscarbonylsubstrateoritsacetalequivalentunderLewisacidcatalysiswasfirstrecognizedbyKuwajimaandNakamurain19771.Thereactiongenerallyledtothegeminalacylationorreductivesuccinoylationofcarbonylsubstrateviatheacid-catalyzedpinacol-typerearrangement(acylmigration)oftheMukaiyamaaldoladductasillustratedinEq.12.OR1R2R1R2OROROR1R2OOR=TMSCO2HOR1R2L.A.acidor(1)OTMSOTMS+Furtherdevelopmentofthisreactionhasbeencarriedoutexten…     

Synthesis of Two Isomeric Tetrasaccharides 0-α-L-Fucopyranosyl-(1→3) and (1→4)-0-(2-Acetamido-2-Deoxy-β-D-Glucopyranosyl)-(1→3)-0-(β-D-Galactopyranosyl)-(1→4)-D-Glucopyranose and a Related Tetrasaccharide 0-α-L-Fucopyranosyl-(1→3)-0-(2-Acetamido-2-Deoxy-β-D-Glucopyranosyl-(1→6)-0-(β-D-Galactopyranosyl)-(1→4)-D-Glucopyranose

ABSTRACT

Synthesis of three tetrasaccharides, namely, 0-α-L-fucopyranosyl-(1→3)-0-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→3)-0-(β-D-galactopyranosyl)-(1→4)-β-D-glucopyranose (7), 0-α-L-fucopyranosyl-(1→4)-0-(2-acetamido-2-deoxy-β-D-glucopyranosyl)-(1→3)-0-(β-D-galactopyranosyl)-(1→4)-D-glucopyranose (9), and 0-α-L-fucopyransoyl-(1→3)-0-(2-acetamido-2-deoxy-β-D-glucopyransoyl)-(1→6)-0-(β-D-galactopyranosyl)-(1→4)-D-glucopyranose (15) has been described. Their structures have been established by ¹³C NMR spectroscopy.     

Preparation of 1,1′-Oxy-bis(3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole) and 2-(N-(p-Toluenesulfonyl)imino)iodobenzylmethyl Ether

Conditions for improved preparation of the crystalline iodine(III) reagents [1,2-C₆H₄(C(CF₃)₂OI)]₂O and 1,2-C₆H₄(CH₂OMe)(I=NTs) are presented together with their x-ray structures. The former is prepared by hydrolysis of 1,2-C₆H₄(C(CF₃)₂OICl (x-ray) and allows the preparation of cyclic sulfates from alkenes; the latter fashions sulfamidate under related conditions.     

The Dissociation Constants of 1,1′-Bis (pyridinium-4-aldoxime)trimethylene dibromide

Summary. The dissociation constants of the two oxime groups of 1,1-bis(pyridinium-4-aldoxime)trimethylene dibromide (TMB-4) were determined using spectrophotometric data. Two numerical methods were applied to treat the overlapping equilibria. The results obtained by both agreed with each other and their mean values at 25°C corrected for the ionic strength of 0.05moldm^–3 are pK_a1=7.49±0.11 and pK_a2=8.96±0.09. These values were discussed in terms of the pK_as of 1,1-bis(pyridinium-4-aldoxime)oxydimethylene dichloride (Toxogonin), a similar dioxime, which were derived by extrapolation of literature data.     

3,3-Bis(2-nitroxyethyl) derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides) as a new type of NO donors

3,3-Bis(2-nitroxyethyl) derivatives of 1,1′-[methylenebis(oxy)]bis(triaz-1-ene 2-oxides) were synthesized by either nucleophilic substitution of the bromine atoms of parent 3,3-bis(2- bromoethyl) compounds or nitration of structurally related 3,3-bis(2-hydroxyethyl) derivatives. The synthesized compounds comprise two different NO donating moieties, namely, oxytriaz- 1-ene 2-oxide and nitrate groups, and, therefore, can be regarded as a new type of NO-donating agents.     

Reactivity of α,α-Dihalogenated Imino Compounds. Part VIII1. Aziridine Formation by Lithium Aluminium Hydride Reduction of N-2-(1,1-Dichloroalkylidene) Cyclohexylamines

1,2-Disubstituted aziridines 2 are not readily accessible and most syntheses remain laborious³. We recently reported⁴ that reaction of α,α-dihalogenated aldimines with lithium aluminium hydride provided a facile synthesis of 1,1-disubstituted aziridines (a three step synthesis starting from ordinary aliphatic aldehydes).     

Synthesis of propyl O-(α-L-rhamnopyranosyl)-(1→3)-[2,4-di-O-(2s-methylbutyryl)-α-L-rhamno-pyranosyl]-(1→2)-(3-O-acetyl-β-D-glucopyranosyl)-(1→2)-β-D-fucopyranoside,the tetrasaccharide moiety of Tricolorin A

Propyl O-(α-L-rhamncpyranosyl)-(1→3)-[2,4-di-O-(2s-methylbutyryl)-α-L-rham-nopyranosyl]-(1→2)-(3-O-acetyl-β-D-glucopyranosyl)-(1→2)-β-D-fucopyranoside (1), the tetrasac-charide moiety of Tricolorin A, was synthesized in total 23 steps with a longest linear sequence of 10 steps, and overall yield of 3.7% from D-Glucose. The isomerization of the dioxolane-type berzyli-dene in the presence of NIS/AgOTf was observed. Tetrasaccharide 1 exhibited no activity against the cultured P388 cell as Tricolorin A did.