Glycosidation of 3,4,6-Tri-O-Benzyl-2-Ethenyl-D-Glucal – A Route to 2-C-(β-Methyl)Methylene Glycosides

ABSTRACT

Monosaccharidic and disaccharidic 2-C-(β-methyl)methylene glycosides were synthesized by an electrophilic conjugate addition reaction of ROH-type compounds in the presence of Ph₃P⁺H Br^? to 2-ethenyl-3,4,6-tri-O-benzyl-D-glucal 1, functioning as a model glycosyl donor. This 2-vinyl glucal derivative represents a series of 2-vinyl and 2-butadienyl glycals, prepared by Wittig-type methylenation of pyranosidic conjugated enals, derived from glucal, galactal and lactal. The exo-(β-methyl)methylene group paves the way for further chemical transformations.     

Syntheses du tri-O-benzyl-3,4,6-D-glucal

The synthesis of 3,4,6 tri-O-benzyl-D-glucal (4) has been accomplished by direct benzylation of triacetylglucal (yield 55%) and by zinc reduction of 3,4,6-tri-O-henzyl-2-acetoxy-1-bromoglucose (yield 26%). The nmr spectra of tribenzyl- and triacetyl-D-glucal in the presence of lanthanide shift reagents were reported.     

Crystal Structure and Solid State 13C Nmr Analysis of Methyl 3,4,6-Tri-O-Acetyl-2-Deoxy-2-(3-Phenylureido)-β-D-Glucopyranoside

ABSTRACT

The X-ray diffraction analysis of methyl 3,4,6-tri-O-acetyl-2-deoxy-(3-phenylureido)-β-D-glucopyranoside was performed and showed that the molecules are associated by two NHz.O=C hydrogen bonds. One molecule with disorder of an acetyl group at C-4 was found in the asymmetric crystal unit. The signals in ¹³C CPMAS NMR spectrum are duplicated indicating that local symmetry is lower than those of the crystal.     

Thymolphthalin as an Analytical Reagent: 1. Spectrophotometric Determination of Ferricyanide and Ferrocyanide

Thymolphthalein (I) as an acid-base indicator is successfully reduced in sodium hydroxide medium and zinc dust into a colorless reagent (Thymolphthalin (III)). The latter is used as an analytical reagent in the colorimetric determination of some mildly strong oxidising agents such as potassium ferricyanide. Ferricyanide, ferrocyanide and a mixture of both are spectrophotometrically determined at 592 nm. Dichromate oxidises ferrocyanide to ferricyanide without interference on the reaction. The results obtained showed that the system does obey Beer's law over the concentration range 20–170 ug ferricyanide per 25ml. The molar absorbitivity is (4.28+0.02)×10³ cm² mg^?1 mole-¹.     

Rhodium‐Mediated Oxygenation of Nitriles with Dioxygen: Isolation of Rhodium Derivatives of Peroxyimidic Acids

Dioxygen is used as the oxygenation agent in the rhodium‐mediated conversion of nitriles into amides. The characterization of intermediate species and model compounds as well as isotope‐labeling studies provided an insight into the reaction mechanism. The conversions of rhodium hydroperoxido or methylperoxido complexes with nitriles into metallacyclic rhodium‐ κ²‐(N,O)‐peroxyimidate compounds represent essential key steps. The former are accessible from a rhodium(III) peroxido complex and the latter represent rhodium derivatives of Payne’s reagent (peroxyimidic acids).     

Reactions of 3-cyanochromones with primary amines: structures of the products

Reactions of 3-cyanochromones with primary aromatic amines in boiling benzene gave mixtures of Z- and E-3-arylamino-2-(2-hydroxyaroyl)acrylonitriles and 2-amino-3-(aryl-iminomethyl)chromones. The latter can easily be obtained in the individual state when the reaction is carried out in the presence of triethylamine. In the case of primary aliphatic amines, the open-chain reaction product immediately undergoes cyclization into 3-alkyliminomethyl-2-aminochromones. The structures of the products were examined by 1D and 2D ¹H, ¹³C, and ¹⁵N NMR spectroscopy in DMSO-d₆ and CDCl₃.     

Total Synthesis of Murrayanine Involving 4,5‐Dimethyleneoxazolidin‐2‐ones and a Palladium(0)‐Catalyzed Diaryl Insertion

A new total synthesis of the natural carbazole murrayanine ( 1 ) was developed by using the 4,5‐dimethyleneoxazolidin‐2‐one 12 as starting material. The latter underwent a highly regioselective Diels–Alder cycloaddition with acrylaldehyde (=prop‐2‐enal; 13 ) to give adduct 14 (Scheme 3). Conversion of this adduct into diarylamine derivative 9 was carried out via hydrolysis and methylation (Scheme 4). Differing from our previous synthesis, in which such a diarylamine derivative was transformed into 1 by a Pd^II‐stoichiometric cyclization, this new approach comprised an improved cyclization through a more efficient Pd⁰‐catalyzed intramolecular diaryl coupling which was applied to 9 , thus obtaining the natural carbazole 1 in a higher overall yield.     

Catalytic Nitrene Transfer To Alkynes: A Novel and Versatile Route for the Synthesis of Sulfinamides and Isothiazoles

A novel transformation is reported for the reaction of terminal or internal alkynes with the nitrene precursor PhI=NTs (Ts=p ‐toluenesulfonyl) in the presence of catalytic amounts of Tp^Br3Cu(NCMe) (Tp^Br3=hydrotris(3,4,5‐tribromo‐pyrazolylborate). Two products containing an imine functionality have been isolated from the reaction mixtures, identified as sulfinamides and isothiazoles. The former correspond to the formal reduction of the sulfone group into sulfoxide, whereas the latter involves the insertion of an alkyne carbon atom into the aromatic ring of the N ‐tosyl moiety.     

Solvent‐Dependent Asymmetric Synthesis of Alkynyl and Monofluoroalkenyl Isoindolinones by CpRhIII‐Catalyzed C−H Activation

The asymmetric synthesis of alkynyl and monofluoroalkenyl isoindolinones from N‐methoxy benzamides and α,α‐difluoromethylene alkynes is enabled by C?H activation with a chiral CpRh^III catalyst. Remarkably, product formation is solvent‐dependent; alkynyl isoindolinones are afforded in MeOH (up to 86 % yield, 99.6 % ee) whereas monofluoroalkenyl isoindolinones are generated in ⁱPrCN (up to 98:2 Z/E, 93 % yield, 86 % ee). Mechanistic studies revealed chiral allene and E‐configured alkenyl rhodium species as reaction intermediates. The latter is transformed into the corresponding Z‐configured monofluoroalkene upon protonation in the ⁱPrCN system and into an alkyne by an unusual anti β‐F elimination in the MeOH system. Notably, kinetic resolution processes occur in this reaction. Despite the moderate enantiocontrol for the formation of the chiral allene, the Z‐monofluoroalkenyl isoindolinones and alkynyl isoindolinones were obtained in good enantiopurities by one or two sequential kinetic resolution processes.     

Saturated nitrogen-containing heterocycles. 15. Catalytic synthesis and isomerization of 9-substituted10-methylperhydroacridines

In the catalytic hydromethylamination of 8-substituted 2-hydroxytricyclo[7.3.1.0^2,7]tridecane-13-ones they are converted into 9-substituted 10-methyl-^9,9a-dodecahydroacridines and 10-methylperhydroacridines with trans,anti,cis- and cis,syn,cis-conformation. The ability of the latter to isomerize into the trans,cis,tans-form has been established.For Communication 14, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 200–204, February, 1992.     

Intramolecular Dynamics of Tetranuclear Iridium Carbonyl Cluster Compounds. Part III. Crystallographic and dynamic evidence for the intermediate of the ‘merry-go-round’ process in nonacarbonyl-μ3-(1,3,5-trithiane)-tetrairidium

The title complex crystallises in two C_3v, isomeric forms differing in carbonyl-ligand arrangement. In solution, the isomer 1b with three edge-bridging carbonyls on a common face of the metal tetrahedron converts via an endothermic equilibrium into the isomer 1u with no bridging carbonyls. The latter was shown by ¹³C-NMR to be the intermediate of the ‘merry-go-round’ process which exchanges the sites of the basal CO's.     

Synthesis of epothilones molecule fragment (15<Emphasis Type="Italic">R</Emphasis>)-C<Superscript><Emphasis Type="Italic">13</Emphasis></Superscript>-C<Superscript><Emphasis Type="Italic">21</Emphasis></Superscript> from D-mannitol

Efficient synthesis of an epothilone molecules fragment (15R)-C¹³-C²¹ was carried out from D-mannitol through its conversion into methyl 2,3-O-cyclohexylidene-D-glycerate followed by the cyclopropanation of the ester group with ethylmagnesium bromide in the presence of titanium(IV) isopropoxide and the transformation of the obtained cyclopropanol into the corresponding 2-substituted allyl bromide. The coupling of the latter catalyzed by copper with 2-methylthiazolyl-4-magnesium bromide, the shift of a double carbon-carbon bond in the product obtained into the position, conjugated with the thiazole ring, and the common transformation of the protected 1,2-diol function afforded the target compound in 15% yield.     

3-Deazaguanine N7- and N9-(2′-Deoxy-β-D-ribofuranosides): Building Blocks for Solid-Phase Synthesis and Incorporation into Oligodeoxyribonucleotides

Oligonucleotides continuing 3-deaza-2′-deoxyguanosine ( I ) or its N⁷-regioisomer 2 were prepared by solid-phase synthesis using P¹¹¹ chemistry. Protection of ¹ or ² with N,N V-dimethylformamide diethyl acetal followed by 4,4′-dimethoxytritylation afforded imidazo[4,5-c]pyridines 10b and 11b , respectively. The latter were converted into the 3′-phosphonates 10c or lie, respectively; the cyanoethyl N,N-diisopropylphosphoramidite 10d was also prepared. The oligonucleotide building blocks were employed in automated solid-phase synthesis. 1 he self-complementary oligomers 13 , 15 , and 17 were prepared and characterized by enzymatic hydrolysis with snake-venom phosphodiesterase followed by alkaline phosphatase. There CD spectra exhibited the general structure of a B-DNA.     

Synthesis of 6β-Halogenodeoxyneopine from Neopine

(-)-Neopine (1), the Δ^8,14 isomer of codeine, occurs as one of the minor constituents in opium from Papaver somniferum L¹. In opium alkaloids of the morphine group the hydroxyl group in position 6 is readily converted with p-toluenesulfonyl chloride or methanesulfonyl chloride into the respective 6α-O-sulfonyl derivatives². The latter in turn form starting materials for the preparation of other derivatives. Thus, with lithium halides, via a S_N2 mechanism³ the 6β-halogen compounds are formed. It is found that, as a result of the allylic system, under slightly changed reaction conditions codeine itself can also yield the 8β-chloro derivative⁴.     

Efficient Syntheses of Methyl 2-Amino-2-Deoxy-3,4,6-Tri-O-Benzyl-α-D-Glucopyranoside and its 2-tert-Butoxycarbonylamino- and 2-Methylamino Derivatives from N-Acetyl-D-Glucosamine

ABSTRACT

The synthesis of the title compounds started with N-acetylglucosamine which was converted into the corresponding methyl glycoside and O-protected with benzyl groups. Subsequent N-protection as its N-BOC-N-acetyl derivative and sequential removal of the N-acetyl group and of the BOC group led in good yield to the target compounds in multigram amounts.     

Reactions of the paramagnetic quaternary Mannich base in an alkaline medium

The catalytic action of aqueous NaOH at 20 °C on 2,2,6,6-tetramethyl-3-(N-methyl-piperidiniomethyl)-4-oxopiperidine 1-oxyl iodide rapidly resulted in the formation (k = 57 L mol⁻¹ s⁻¹) of a paramagnetic ketone with an activated double bond: 2,2,6,6-tetramethyl-3-methylidene-4-oxopiperidine 1-oxyl. The latter underwent slow transformation into a nitroxyl biradical containing an activated double bond and a methylene bridge linking positions 3 and 3′. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 421–423, February, 2008.     

A new method for the synthesis of N-substituted (4-oxo-4,5,6,7-tetrahydroindol-3-yl)acetic acids

A new method for the synthesis of N-substituted 2-(4-oxo-4,5,6,7-tetrahydroindol-3-yl)acetic acids was developed. Alkylation of cyclic 1,3-diketones with 3,5,5,5-tetrachloropentan-2-one affords 1,4-diketones, which undergo cyclization with different primary amines into N-substituted 3-(2,2,2-trichloroethyl)-4,5,6,7-tetrahydroindol-4-ones. Acid hydrolysis of the latter gives the corresponding indol-3-ylacetic acids. The structures of the compounds obtained were confirmed by ¹H and ¹³C NMR data.     

3‐O‐Acetyl‐4‐deoxy‐4‐iodo‐β‐d‐fructo­furan­osyl 2,3,6‐tri‐O‐acetyl‐4‐chloro‐4‐deoxy‐α‐d‐gluco­pyran­oside

At 160 K, the gluco­pyran­osyl ring of the title compound, C₂₀H₂₈ClIO₁₃, has a near‐ideal ⁴C₁ conformation and the fructo­furan­osyl ring has a twist ⁴T₃ conformation. The two hydroxy groups are involved in intra‐ and intermolecular hydrogen bonds, with the latter interactions linking the mol­ecules into infinite one‐dimensional chains. The absolute configuration of the mol­ecule has been determined.     

The role of ion pairing in the chromatographic study of propranolol analogues

Summary The partition coefficients, logP _app ^RPLC, for a series of propranolol analogues have been determined by reversed phase high performance liquid chromatography. The hydrochloride salts and free base logP _app ^RPLC show that charged and uncharged species can partition into the reversed phase. An extrathermodynamic relationship was found for logP _app ^RPLC measured in two different column stationary phases, C8 and PMOS, suggesting that the same set of compounds experience a similar trend in these elution systems. The importance of using phosphate and/or MOPS buffer is due to the fact that the latter can avoid ion-pairing partitioning, but the former does play the same role for PMOS column when the free base is considered.     

Solution Stoichiometry Control for Pure LiLaMo2O8Phases in Sol-Gel Preparation

The hydrolysis of solutions, containing either LiMo₂O₄(OPr ⁱ )₅( ⁱ PrOH) and “La(OPr ⁱ )₃” or LiOPr ⁱ and La₂Mo₄O₈(OPr ⁱ )₁₄ in 1∶1 ratio, in toluene or ⁱ PrOH, by water solutions in isopropanol, leads to formation of monolythic gels. The latter can be converted by drying and heat treatment at 600°C into a fine powder of pure α-LiLaMo₂O₈ phase, which is transformed into β-LiLaMo₂O₈ powder by annealing at 800°C. The sintering of the pellets pressed under 4 bar pressure of α-LiLaMo₂O₈ powder at 800°C for 2 h converts them into pieces of β-LiLaMo₂O₈ transparent ceramics, thus providing a route to LiLnMo₂O₈ laser waveguide materials.