Synthesis of (2R,3S,4S)-4-aryl-3-hydroxyprolinols

Synthesis of (2R,3S,4S)-4-aryl-3-hydroxyprolinols has been established starting from 2-benzyloxymethylpyrrolidin-2-one framework, which is derived from commercially available trans-(2S,4R)-4-hydroxyproline. The single diastereomer having a trans–cis relative configuration with C₂ and C₃ and C₃ and C₄ is constructed in two one-pot functional group transformations of Grignard addition/dehydration and epoxidation/isomerization as the key steps in moderate yield.     

Ru- and Fe-based N,N′-bis(2-pyridylmethyl)-N-methyl-(1S,2S)-1,2-cyclohexanediamine complexes immobilised on mesoporous MCM-41: Synthesis, characterization and catalytic applications

Protected mesoporous MCM-41 phases were synthesized by grafting of the ligand, (1S,2S)-N,N′-bis-pyridin-2-ylmethyl-cyclohexane-1,2-diamine (L₂Me), through the reactive 3-chloropropyltrimethoxysilane (3-CPTMS) group and designated as L₂Me-MCM-41. Subsequently, RuCl₃ and Fe(BF₄)₂ or Fe(CF₃SO₃)₂ were added to the heterogenized L₂Me-MCM-41 for complexation and designated as M-L₂Me-MCM-41 (M = Ru and Fe). All samples were characterized in detail using XRD, N₂ sorption isotherm, FT-IR, TGA-DTA, XPS, UV–vis, solid state ¹³C NMR, EPR and elemental analysis, etc. The XRD and sorption measurements of the catalyst confirmed the structural integrity of the mesoporous hosts and the spectroscopic characterization techniques proved the successful anchoring of the metal complexes over the modified mesoporous support. The screening of catalyst M-L₂Me-MCM-41 was done for the oxidation reaction of thioanisole (methyl phenyl sulphide) using H₂O₂ as an oxidant. The Ru-L₂Me-MCM-41 and Fe-L₂Me-MCM-41 catalysts show higher activities and turnover numbers and exhibit enantiomeric excess comparable to the homogeneous catalysts, Ru-L₂(Me)₂ and Fe-L₂(Me)₂. Furthermore, Fe-L₂Me-MCM-41 and Fe-L₂(Me)₂ were also found active in the epoxidation of styrene. These results indicate that metal complexes are confined into the pore of the material which play a major role in the reaction.     

Design, synthesis, structure and properties of an α-helix cap template derived from N-[(2S)-2-chloropropionyl]-(2S)-Pro-(2R)-Ala-(2S,4S)-4-thioPro-OMe which initiates α-helical structures

A strategy based upon removing the requirement for all of the carbonyl dipoles to align at the same time in the transition state leading to the cyclisation of N-[(2S)-2-chloropropionyl]-(2S)-Pro-(2R)-Ala-(2S,4S)-4-thioPro-OMe to a Zimm-Bragg type α-helix peptide intitator template was successful. Each amide bond of the 12-membered macrocyclic template existed in the trans-rotomeric form. Derivatives of the template were prepared by extending the C-terminus and these were characterised by NMR spectroscopy and restrained simulated annealing. In deuterochloroform solution at low temperature, separate sets of NMR signals were observed for two rapidly interconverting helical conformational isomers of the thioether macrocycle which possessed an appended trialkylammonium ion. A similar time-averaged conformation was also observed in aqueous solution. At −80 °C in d₂-dichloromethane the rate of conformational exchange was slowed sufficiently to obtain resonance assignments and NOE data separately for each isomer. In the minor isomer (40%), the four carbonyl oxygen hydrogen-bond acceptors of the template are aligned in an α-helical conformation and in the major conformer the Pro² carbonyl dipole was anti-aligned with the other three dipoles. Thus, the conformers differ in the orientation of one carbonyl group. Molecular modelling calculations showed that the minor isomer was stabilised by coulombic interactions between the trialkylammonium salt and the carbonyl group dipole moments.     

Stereoselective total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone

The total synthesis of (+)-(6R,2′S)-cryptocaryalactone and (−)-(6S,2′S)-epi cryptocaryalactone is reported based on stereoselective reduction of δ-hydroxy β-keto ester to install 1,3-polyol system, cis Wittig olefination, and lactonization as the key steps. The synthesis of (−)-(6S,2′S)-epi cryptocaryalactone is also reported using syn-benzylidene acetal formation and a preferential Z-Wittig olefination reaction and lactonization as the key steps.     

The stereochemistry of the dichlorocobalt(III) complexes with (2S,5S,9S)- and (2S,5R,9S)-trimethyltriethylenetetraamines

Dichlorocobalt(III) complexes of (2S,5S,9S)-trimethyltriethylenetetraamine (L₁) and (2S,5R,9S)-trimethyltriethylenetetraamine (L₂) have been prepared. Both L₁ and L₂ coordinate to the cobalt(III) ion to give three isomers: Λ-cis-α, Δ-cis-β, trans isomers for L₁ and Δ-cis-α, Δ-cis-β, trans isomers for L₂. Each of the trans-dichloro complexes of the two ligands have been isomerized stereospecifically to the cis-α-dichloro complex in methanol, and each of the cis-α-dichloro complexes stereospecifically to the trans-diaqua complex in water. Both the geometrical and optical inversions took place at the same time in the observed stereospecific isomerizations.     

A new chiral coordination polymer based on [Fe(CN)6]4?, Cu2+ cations, and (2 S , 3 S )-1,2,3,4-tetraaminobutane: Synthesis, structure, and ESR spectra

The new chiral coordination polymer [{Cu(NH₃)(threo-tab)}₂Fe(CN)₆]·8H₂O was synthesized by the reaction of an aqueous solution of potassium hexacyanoferrate with an ammonia solution of copper(II) chloride and (2S,3S)-1,2,3,4-tetraaminobutane (threo-tab). The structure of the coordination polymer was established by X-ray diffraction. The ESR spectra of this compound were measured for a powder and a single crystal. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 437–440, March, 2007. Universit?t des Saarlandes, Anorganische Chemie, Saarbrücken, Germany.     

Y型分子筛固载(1S,2S)-DPEN-Ru(TPP)2催化苯乙酮不对称加氢

采用自由配体法将(1S,2S)-DPEN(1,2-diphenyl-1,2-ethylene-diamine)-Ru(TPP)2(TPP=三苯基膦,triphenylphosphine)配合物封装于NaY沸石分子筛超笼中,制备了(1S,2S)-DPEN-Ru(TPP)2/Y主客体材料(1S,2S)-DPEN=1,2-二苯基-1,2-乙二胺).采用等离子体发射光谱ICP、粉末X射线衍射(XRD)、紫外光谱(UV-Vis)、氮吸附等物理化学手段对所制备材料进行了表征.结果表明,(1S,2S)-DPEN-Ru(TPP)2配合物封装于Y型分子筛超笼中保持了原有的物理化学性能;作为苯乙酮不对称加氢催化剂,在优化条件下,苯乙酮的转化率可达100%,(R)-苯乙醇的对映体过量值(ee值)可达61.0%.该催化剂具有良好的稳定性和重复使用性.     

Synthesis and Structural Determination of (2R,4S,SS)-( )-Threo-5-(2,2-dichloroacetamido)-4-(4-nitrophenyl)-2-aryl-1,3-dioxanes

Acetalscanbesynthesizedinanumberofways.Themainproblemintheacetalformationinacidicmediumistoshifttheequilibriumtotherightbyremovalofthewaterformedduringthereactionl.Wesynthesized(2R,4S,SS)-( )-threo-5-(2,2-dich(4-nitrophenyl)-2-aryl-1,3-dioxanesbyacet...     

Enantioselective organic syntheses using chiral transition metal complexes V. (2S,3S)-Bis(dibenzophospholyl)butane, a rigid (S,S)-CHIRAPHOS analog

The P–Ph cleavage of phenyldibenzophosphole (1) with lithium in THF gives lithium dibenzophospholide (2). Reaction of 2 with ethyleneglycol ditosylate produces the known chelate ligand 1,2-bis(dibenzophospholyl)ethane (3) in good yield. Similarly, 2 and (2R,3R)-butanediol ditosylate give the new chiral chelate ligand (2S,3S)-bis(dibenzophospholyl)butane (4). Ligand exchange of [CpRu(PPh₃)₂Cl] with 3 or 4 yields the halfsandwich complexes [CpRu(C₁₂H₈PC₂H₄PC₁₂H₈)Cl] (5) and [CpRu((S,S)-C₁₂H₈PCHMeCHMePC₁₂H₈)Cl] (6). Complex 6 was characterized crystallographically (monoclinic, space group P2₁ (no. 4), a=820.6(4), b=1501.0(3), c=1172.8(6) pm, β=108.87(2)°, V=1.367(1)×10⁹ pm³, Z=2). The most conspicuous feature of the structure of 6 is the perfect coplanarity of the two dibenzophosphole moieties imposed by their steric interaction with the Cp ligand. Complex 6 and the thiophene complex [CpRu((S,S)-C₁₂H₈PCHMeCHMePC₁₂H₈)(SC₄H₄)]BF₄ (7) derived therefrom are remarkably unreactive with regard to ligand substitutions. A possible explanation is the lack of intramolecular

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–C stabilization en route to the transition state of ligand substitution. The enantiomeric purity of 6 and 7 could nevertheless be demonstrated by conversion to diastereomerically pure [CpRu((S,S)-C₁₂H₈PCHMeCHMePC₁₂H₈)((S)-CNCHMePh)]BF₄ (8).     

(R)-4-menthen-3-one in the synthesis of (3S)-methylundecand (2S)-methyldec-1-ylbromides, key synthons for (S,S,S)-diprionylacetate

New capabilities for the synthetic use of (R)-4-menthen-3-one were demonstrated using as examples (3S)-methylundec- and (2S)-methyldec-1-ylbromides, key synthons for (S,S,S)-diprionylacetate (sex pheromone of pine sawflies of genera Diprion and Neodiprion).     

Diastereoselective allylation of N-glyoxyloyl-(2R)-bornane-10,2-sultam and (1R)-8-phenylmenthyl glyoxylate: synthesis of (2S,4S)-2-hydroxy-4-hydroxymethyl-4-butanolide

The diastereoselective addition of allylsilanes and allylstannanes to N-glyoxyloyl-(2R)-bornane-10,2-sultam 1 and (1R)-8-phenylmenthyl glyoxylate 7 in the presence of Lewis acids has been studied. We obtained diastereoselectivities up to 84% and 94% for the allylation of 2 and 7, respectively. The application of the allylation products of 1 or 2 in the synthesis of 4-butanolides, for example (2S,4S)-2-hydroxy-4-hydroxymethyl-4-butanolide 13 is presented.     

Spectroscopic characterization and single molecule structures of N,N-bis-(3-phthalimidopropyl)-N-(2-hydroxyethyl)-N-propylammonium salts and their hydrates

N,N-Bis-(3-phthalimidopropyl)-N-(2-hydroxyethyl)-N-propylammonium salts and their hydrates have been characterized by FTIR, Raman and NMR spectroscopy. Also B3LYP and PM5 calculations have been carried out. The optimized bond lengths, bond angles and torsion angles calculated by B3LYP/6-31G(d,p) approach have been compared with the spectroscopic data. The screening constants for ¹³C and ¹H atoms have been calculated by the GIAO/B3LYP/6-31G(d,p) approach and analyzed. Linear correlations between the experimental ¹H and ¹³C chemical shifts and the computed screening constants confirm the optimized geometry.     

微波辅助铜合成2-(N,N-二甲氨基)苯并噁唑衍生物

建立了一种简单实用、经济高效的以取代2-碘芳胺和N,N-二甲基氨基硫代甲酰氯为原料,以碘化亚铜为催化剂,吡啶为溶剂,100 ℃条件下,串联合成2-(N,N-二甲氨基)苯并噁唑衍生物的微波催化体系,合成了一系列中等至良好产率的2-(N,N-二甲氨基)苯并噁唑衍生物,最高产率达90%。     

Asymmetric Synthesis of （R）- and （S）-Moprolol

A simple and effective procedure for the enantioselective synthesis of （R）- and （S）-moprolol was described. The key step was the asymmetric synthesis of enantiopure （R）- and （S）-guaifenesin, which were synthesized from enantioenriched （R）-3-chloro-l,2-propanediol and （S）-epichlorohydrin via kinetics of hydrolysis resolution of racemic epichlorohydrin by chiral Salen-Co^Ⅲ complex. The e.e. values of both the optical compounds were above 98%, and the chemical structures of the target compounds were confirmed by ^1H NMR, ^13C NMR, IR, and MS.     

20 （S） -20-O- Camptothecin β-Aminopropionate： Novel Synthesis and Antitumor Activity in vitro

IntroductionCamptothecin(CPT,1, Scheme 1), a pentacyclicalkaloid isolated from theCamptotheca acuminatebyWallet al. in 1966, shows a broad-spectrum antitumoractivity[1]. However, because of its lowwater solubilityand high toxicity, its clinical applicatio…     

A new and general synthesis of chiral β-ketosulfoxides by reaction of (+)-(R)-methyl p-tolyl sulfoxide with nitriles

The nitrile functional group is efficiently transformed into the β-ketosulfoxide moiety by reaction with the anion formed from (+)-(R)-methyl p-tolyl sulfoxide and aqueous acidic work-up of the reaction.     

Synthesis of 2-(ethylsulfanyl)aniline derivatives through the unexpected ring opening of N-substituted-2(3H)-benzothiazolones

The decarbalkoxylations of disubstituted geminal diesters by water–DMSO with added salts (KCN or NaCN) is a convenient preparative route leading to the corresponding monoesters. Herein, we described an efficient and very simple methodology for the preparation of 2-(ethylsulfanyl)aniline derivatives through the unexpected ring opening of the corresponding N-substituted-2(3H)-benzothiazolones in the presence of disubstituted geminal diester, KCN, and water–DMSO.     

Substituted pyridine coordinated N,N-trans and N,N-cis cyclopalladated complexes of (S)-4-tert-butyl-2-phenyl-2-oxazoline: Crystal structures, spectral study and catalysis of the decomposition of PS pesticides

Three pyridine coordinated cyclopalladated complexes: (S)-chloro{2-[2-(4-tert-butyl)oxazolinyl]phenyl-C,N}(4-R-pyridine)palladium(II) (R = H, 2; R = CF₃, 3; R = NMe₂, 4), have been synthesized and structurally characterized. While the crystal structure shows that 2 has a normal N,N-trans-conformation in the coordination sphere of palladium(II), 3 and 4 exhibit uncommon N,N-cis-conformations. From ¹H NMR measurements, the major coordination isomer in deuterated chloroform solution is N,N-trans configuration for three palladacycles. It was found that the three complexes catalyze effectively the methanolysis of the PS pesticides including chiral thiophosphates but show different activity depending on the substituents of co-coordinated pyridine ring in 2–4.     

Comparison of the chiral resolution on cis-trans isomeric chiral stationary phases derived from (S)-1-(1-naphthyl)ethylamine

A pair of cis-trans isomeric chiral stationary phases (CSPs) derived from (S)-1-(1-naphtyl)ethylamine was prepared. The chromatographic behaviours on both CSPs with regard to the resolution of enantiomeric amino acids, amino alcohols, amines, and carboxylic acid were studied. According to separation factors, the trans-CSP showed better chiral recognition ability for the separation of most analytes chosen in this study. Three homologous series of the alkyl esters of racemic amino acids were resolved on both CSPs using n-hexane-2-propanol and n-hexane-dichloromethane as mobile phases. The trans-CSP also showed better enantioselectivity for the resolution of homologues. A reverse of elution order was observed for the resolution of the homologous series of phenylglycine alkyl esters on both CSPs. It was found that the relationship between the separation factor and the alkyl chain length of the ester homologous series depended upon the components of mobile phase. A higher magnitude of difference between the two CSPs in enantioselectivity for the resolution of a given homologue was obtained when n-hexane-dichloromethane was used as a mobile phase. A chiral recognition process, in which steric repulsion, face-to-face π-π interaction, face-to-edge π-π interaction and hydrogen bonding interaction were involved, was also suggested to describe the separation of enantiomeric homologues on both CSPs. This study clearly indicates that the chiral resolution is influenced by the geometry of the double bond in a CSP.     

Stereoselective Synthesis of (7aS)-1-Methylenehexahydro-1H-pyrrolizine and (?)-Heliotridane from N-Diphenylmethyl-(S)-proline Ethyl Ester

Alkaloid (7aS)-1-methylenehexahydro-1H-pyrrolizine was synthesized from N-diphenylmethyl-(S)-proline ethyl ester by cyclopropanation of the ester group with ethylmagnesium bromide in the presence of titanium tetraisopropoxide, replacement of the protecting group on the nitrogen atom, and cationic cyclopropylallyl isomerization of (S)-1-(1-ethoxycarbonylpyrrolidin-2-yl)cyclopropyl sulfonate into the corresponding allyl bromide. Stereoselective reduction of (7aS)-1-methylenehexahydro-1H-pyrrolizine with sodium tetrahydridoborate in the presence of nickel chloride afforded (−)-heliotridane [(1S,7aS]-1-methylhexahydro-1H-pyrrolizine] in high yield.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 1, 2005, pp. 73–77.Original Russian Text Copyright © 2005 by Lysenko, Kulinkovich.