Synthesis of β-chloro α-amino acids: (2S,3R)- and (2S,3S)-3-chloroleucine

The first syntheses of (2S,3R)- and (2S,3S)-3-chloroleucine (3-chloro-d-leucines 1 and 2) have been achieved from d-3-hydroxyleucine and allo-d-3-hydroxyleucine, respectively, through the formation of the corresponding N-Cbz β-lactones, followed by a ring opening promoted by lithium chloride and a debenzylation process.     

Enantioselective synthesis of (2R,3R)- and (2S,3S)-β-hydroxyornithine

An efficient and short synthesis of (2R,3R)- and (2S,3S)-β-hydroxyornithine 1a-b is described using Sharpless asymmetric dihydroxylation and regioselective nucleophilic opening of a cyclic sulfite as the key steps.     

4-{[(1E)-(2-Hydroxyphenyl)methyl­idene]amino}-1,5-dimethyl-2-phenyl-2,3-dihydro-1H-pyrazol-3-one

In the title compound, C₁₈H₁₇N₃O₂, a strong intramolecular O—H⃛N hydrogen bond [N⃛O 2.607 (3), O—H 0.97 (3) and H⃛N 1.71 (3) Å, and O—H⃛N 153 (2)°] was observed, which leads to a unique phenol–imine tautomerism in the solid state. The C=N imine bond distance and the C—N—C bond angle [1.287 (2) Å and 121.7 (1)°, respectively] indicate the existence of this phenol–imine tautomer. In solution, the phenol–imine tautomer of the title free Schiff base ligand is dominant in both polar and non-polar solvents, as supported by ¹H NMR and UV–visible spectroscopic data.     

Synthesis of (E)- and (Z)-α,β-difluorourocanic acid

Horner-Emmons fluoroolefination of an aryl aldehyde followed by introduction of a second fluorine via “FBr” addition provides an original approach to the preparation of 1-alkyl-2-aryl-1,2-difluoroethenes. The utility of this procedure is demonstrated by the preparation of (E and Z)-α,β-difluorourocanic acid.     

Reagent-controlled diastereoselective synthesis of (2S,3R)- and (2R,3R)-2,3-diaminobutanoic acid derivatives using proline-catalyzed α-hydrazination reaction

(2S,3R)- and (2R,3R)-2,3-Diaminobutanoic acid (Dab) derivatives were efficiently synthesized from Cbz-(R)-alanine using the proline-catalyzed diastereoselective α-hydrazination reaction and the SmI₂-promoted reductive cleavage of the N-N bond as the key steps.     

The first stereoselective total synthesis of (3S,4R)-dihydroxy-(6S)-undecyl-α-pyranone and total synthesis of (2S,3R,5S)-(−)-2,3-dihydroxytetradecan-5-olide

The first total synthesis of (3S,4R)-dihydroxy-(6S)-undecyl-α-pyranone 1 and total synthesis of (2S,3R,5S)-(−)-2,3-dihydroxytetradecan-5-olide 2 have been achieved in five steps in a highly stereoselective manner using Maruoka allylation, olefin cross-metathesis, and Sharpless asymmetric dihydroxylation as key steps.     

Stereoselective synthesis of (22Z)-25-hydroxyvitamin D2 and (22Z)-1α,25-dihydroxyvitamin D2

Two new vitamin D₂ analogues, (22Z)-25-(OH)-D₂ and (22Z)-1α,25-(OH)₂-D₂, were serendipitously synthesized from vitamin D₂ and using the Julia-Kocienski olefination.     

The first asymmetric total synthesis of (R)-tuberolactone, (S)-jasmine lactone and (R)-δ-decalactone

A general synthetic approach has been developed for the first asymmetric total synthesis of tuberolactone 1, jasmine lactone 2 and δ-decalactone 3. The key step is the selective hydrogenation of triple and endocyclic double bonds in the key intermediate 4.     

Host compounds (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and (2R,3R)-(−)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) with guests o-, m- and p- toluidine: A comparative investigation

In this work, we have compared the host abilities of closely related compounds (+)-(2R,3R)-1,1,4,4-tetraphenylbutane-1,2,3,4-tetraol (TETROL) and (2R,3R)-(?)-2,3-dimethoxy-1,1,4,4-tetraphenylbutane-1,4-diol (DMT) when these were recrystallized from single and mixed toluidine guests. Significant differences in host behaviour and selectivities were revealed and these were explained by means of single crystal diffraction experiments. Thermal analyses were used to determine the relative complex stabilities, and these data correlated exactly with the host selectivity orders for both TETROL and DMT.     

Ruthenium(II) nitro-nitroso-bis-{1-(alkyl)-2-(β-napthylazo)imidazole}: Synthesis,spectroscopy, electrochemistry and reactivity

Aquation of blue cis-trans-cis-[RuCl₂(β-NaiR)₂] (1) leads to the synthesis of solvento species, blue-violet cis-trans-cis-[Ru(OH₂)₂(β-NaiR)₂](ClO₄)₂ (2), [β-NaiR = C₁₀H₇-N=N-C₃H₂-NN, abbreviated as N,N′-chelator, R = Me] that have been reacted with NaNO₂ in warm EtOH resulting in violet dinitro complexes of the type, [Ru(NO₂)₂(β-NaiR)₂] (3). The nitrite complexes are useful synthons of electrophilic nitrosyls, and on triturating the dinitro compounds with cone. HClO₄ nitro-nitrosyl derivatives, [Ru(NO₂)(NO)(β-NaiR)₂]²⁺ (4) are isolated. The chemical oxidation of aqua complex (2) by excess aqueous eerie solution in 1 (N) H₂SO₄ leads to the spontaneous formation of a yellow colored species. The electrophilic behaviour of metal bound nitrosyl has been proved by reacting with a bicyclic ketone, camphor, containing an active methylene group and an arylhydrazone with an active methine group. The diazotization of the primary aromatic amines with a strongly electrophilic mononitrosyl complex in acetonotrile and dichloromethane solution was thoroughly studied. Electrocatalytic oxidation of benzyl alcohol was examined.     

SmI2-induced cyclization of optically active (E)- and (Z)-β-alkoxyvinyl sulfoxides with aldehydes

SmI₂-induced reaction of (E)-β-alkoxyvinyl (R)- and (S)-sulfoxides with aldehydes effected a highly stereoselective intramolecular cyclization to give 2,6-anti-2,3-cis- and 2,6-syn-2,3-trans-tetrahydropyran-3-ols, respectively. The reaction of (Z)-(R)-isomer gave 2,6-syn-2,3-cis-tetrahydropyran-3-ol and a ring-opened product, and that of (Z)-(S)-isomer yielded many products.     

9-α-Nitro(hydroxy,amino)benzylidene- and 9-Hydroxy(amino)methylene-4-azafluorenes

Nitration of 9-benzylidene-4-azafluorene with acetyl nitrate leads to the formation of its 9--nitrobenzylidene derivative; reduction of the latter gives the corresponding enamine and oxime. Reaction of 4-azafluorene with ethyl benzoate and ethyl formate gives the hydroxybenzylidene and hydroxymethylene derivatives, which upon condensation with amines generate the corresponding enamines. Reduction of 9-formylazafluorene oxime gives 9-aminomethyleneazafluorene. All of the newly synthesized compounds were isolated in the form of mixtures of their Z- and E-isomers, and their structures were established using PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 212–217, February, 1991.     

The synthesis,characterization and spectral studies of Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes with N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl) methyl]amino}butyl) N′,N′-dihydroxyethanediimidamide

Co^II, Ni^II, Cu^II, Zn^II and Cd^II complexes of N,N-bis(2-{[(2-methyl-2-phenyl-1,3-dioxolan-4-yl)methyl]amino}butyl)N′,N′-dihydroxyethanediimidamide (LH₂) were synthesized and characterized by elemental analyses, IR, ¹H- and ¹³C-NMR spectra, electronic spectra, magnetic susceptibility measurements, conductivity measurements and thermogravimetric analyses (TGA). The Co^II, Ni^II and Cu^II complexes of LH₂ were synthesized with 1?:?2 metal ligand stoichiometry. Zn^II and Cd^II complexes with LH₂ have a metal ligand ratio of 1?:?1. The reaction of LH₂ with Co^II, Ni^II, Cu^II, Zn^II and Cd^II chloride give complexes Ni(LH)₂, Cu(LH)₂, Zn(LH₂)(Cl)₂, Cd(LH₂)(Cl)₂, respectively.     

{[(n-Bu)2Sn(O2CCH=CHAr)]2O}2的合成、表征和{[(n-Bu)2Sn(O2CCH=CHPh)]2O}2的晶体结构

利用(n-Bu)2SnO与ArCH=CHCO2H反应,合成5个二聚二丁基锡芳基丙烯酸酯氧化物{[(n-Bu)2Sn(O2CCH=CHAr)]2O}2.通过元素分析、红外光谱和核磁共振氢谱对其结构进行了表征.用X射线单晶衍射测定了{[(n-Bu)2Sn-(O2CCH=CHPh)]2O}2 (1)的晶体结构,结果表明,化合物1是以Sn2O2四面体为中心的,中心对称的二聚体结构,内环锡为五配位的畸变三角双锥构型,外环锡为六配位的畸变加帽体三角双锥结构.该化合物属三斜晶系,空间群P1-, a=1.0172(11) nm, b=1.3804(16) nm, c=1.4703(17) nm, α=106.750(18)°, β=105.61(2))°, γ=100.295(18)°, Z=1, V=1.829(4) nm-3, Dc=1.413 g/m3, μ=1.400 mm-1, F(000)=792, R=0.0559, wR=0.1250.     

Synthesis of dipyrrolo[2,3-a:1′,2′,3′-fg]acridin-12(1H)-ones

Acylation reactions of 4,6-dimethoxyindoles with glyoxyloyl chlorides were achieved by the use of graphite powder in 1,2-dichloroethane at reflux. The products were monoketones as a result of decarbonylation, rather than the expected 1,2-diketones. Treatment of these monoketones with base led to their cyclisation and elimination of methanol to afford the novel dipyrrolo[2.3-a:1′,2′,3′-fg]acridin-12(1H)-ones.     

Crystal Structure of Methyl 3- (2-chlorophenyl )-3- (5, 5-dimethyl-3-hydroxy-2-cyclohexene- 1-one-2-yl) propionate

1INTRODUCTIONInorganicsolidsupportsascatalystshavebeenwellstudied,becauseoftheirap-plicationsinorganicsynthese('~".Recently,wehavereportedtheKnoevenagelcon-densationcatalysedbyKF-Al,O,['i.Inthispaper,wediscussedthecrystalstruc-tureofthetitlecomPoundsynthesizedbythereactionof2-chlorobenzaldehydey5,5-dimethyl-1,3-cyclohexanedioneandisopropylidenemalonateinmethanolcatalyzedbyKF-Alzo,'Inordertoconfirmthestructureofthetitlecompound,theX-raycrys-tallOgraphicstudywascarriedout.2EXPER1MEN…     

Synthesis and structure of {{amino(triorganosilyl)carbene}pentacarbonyltungsten(0)} complexes and attempted synthesis of {[2-bis(trimethylsilyl)methyl-3-triorganosilyl-2H-azaphosphirene-κP]pentacarbonyltungsten(0)}

First examples of tungsten aminocarbene complexes [(OC₅)W{C(SiR¹_nR²_3-n)NH₂}] 2a-d (R¹ = Ph, R² = Me) were synthesized via ammonolysis of the corresponding methoxycarbene complexes 1a-d. They were characterized by NMR spectroscopy, MS, IR, UV/Vis and elemental analysis, and in the case of the C-triphenylsilyl derivative 2a by single-crystal X-ray structure analysis. The reaction of P-chloro alkylidenephosphane 3 with complexes 2a-d, meant to give 2H-azaphosphirene complexes, was monitored by ³¹P NMR spectroscopy to reveal the formation of the products 4-7, which were presumably formed via decomposition of the transient complexes 10a-d.     

Enantioselective epoxidation of α,β-enones promoted by (1R,3S,4S)-2-azanorbornyl-3-methanol as an organocatalyst

(1R,3S,4S)-2-Azanorbornyl-3-methanol was synthesized form (R)-1-phenylethylamine and used as a catalyst for the enantioselective epoxidation of α,β-enones to afford the corresponding epoxides in good yields and high enantioselectivities at room temperature.     

A facile and efficient synthesis of fully substituted pyridin-2(1H)-ones from α-oxoketene-S,S-acetals

A facile and efficient synthesis of fully substituted pyridin-2(1H)-ones has been developed by the reaction of readily available α-oxoketene-S,S-acetals with malononitrile in the presence of sodium methoxide in methanol under reflux.     

Photochemistry of β-(4-sydnonyl)-o-divinylbenzene: competitive cis-trans isomerization and photolysis

New cis- and trans-3-aryl-4-[2-(2-vinylphenyl)ethenyl]sydnones 2, aryl = phenyl, p-tolyl were prepared and transformed on irradiation in the presence of acrolein to a pyrazoline derivative that aromatized during isolation to trans-1-tolyl-3-[2-(2-vinylphenyl)ethenyl]pyrazole 7 and trans-5-formyl-1-tolyl-3-[2-(2-vinylphenyl)ethenyl]pyrazole 8.