Conduramine F-1 epoxides: synthesis and their glycosidase inhibitory activities

Starting from (±)-7-oxanorbornenone ((±)-14), (±)-(1RS,2RS,3SR,6SR)-6-azidocyclohex-4-en-1,2,3-triol ((±)-24) and (±)-(1RS,2RS,3SR,6RS)-6-azidocyclohex-4-en-1,2,3-triol ((±)-26) were obtained. Epoxidation of the latter cyclohexene derivative gave two epoxides (±)-30 and (±)-31 that were converted into (±)-conduramine F-1 epoxides (±)-10 and (±)-11 and N-substituted derivatives (±)-12 and (±)-13. Compound (±)-(1RS,2SR,3RS,4SR,5RS,6SR)-5-({[4-(trifluoromethyl)phenyl]methyl}amino)-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-12c) is a good, non-competitive inhibitor of β-xylosidase from Aspergillus niger (K_i=2.2 μM), and (±)-(1RS,2RS,3SR,4RS,5SR,6SR)-5-{[(biphenyl-4-yl)methyl]amino}-7-oxabicyclo[4.1.0]heptane-2,3,4-triol ((±)-13d) is a good inhibitor of α-glucosidase from brewer's yeast (K_i=2.8 μM, non-competitive).     

Catalyst free,regioselective one-pot three-component synthesis of thiazol-2-imine derivatives in ionic liquid

A one-pot three-component approach for the synthesis of thiazol-2-imines has been described by the reaction of amine, phenyl isothiocyanate and β-nitroacrylate in [Hbim]BF₄ ionic liquid. The method is applicable for aromatic, benzylic, aliphatic and cyclic amines. Reusable reaction media, regioselectivity, mild reaction condition, catalyst free and high yield of products are the salient features of this protocol.     

Structure elucidation and stereoselective total synthesis of pavettamine, the causal agent of gousiekte

The structure elucidation of a novel natural product pavettamine (1), the causal agent of the plant toxicosis gousiekte, is reported. The structure was defined by analysis of NMR and MS data and the relative configuration followed from the ¹³C NMR data of the acetonide derivative. The absolute stereochemistry was established by total synthesis from (2S)-malic acid using chiral sulfoxide methodology as (2S,4R,8R,10S)-1,11-diamino-6-aza-undecane-2,4,8,10-tetraol.     

Highly diastereoselective synthesis of 2-substituted-1,3-diols catalyzed by ketoreductases

The stereoselective reduction of α-substituted-β-hydroxy ketones for the preparation of the corresponding optically pure 2-monosubstituted or 2-disubstituted-1,3-diols is described. These transformations proceed in high optical purities and yields. Ketoreductases were able to catalyze the formation of either the syn or the anti diol, depending on the enzyme. By replacing the α-alkyl substituent for an OAc moiety, in low conversion time (≤24 h), ketoreductases catalyzed the formation of the OAc-protected 1,2,3-triol, in high yield and with high optical purity (>99% de, >99% ee). This is a simple and highly stereoselective method for the synthesis of different diastereomers of chiral diols.     

H_2BPMPBD和DAM协同萃取部分Ln(Ⅲ)

4 酰代双吡唑啉酮是以吡唑酮为端基、脂肪族碳氢取代基联结而成的一类新型非环四齿酸性螯合剂[1 ,2 ] ,螯合功能团比普通的 4 酰代吡唑酮多一倍 ,对金属离子具有很强的萃取能力 ,其中对Ｆｅ(Ⅲ )、Ｃｏ(Ⅱ )、Ｎｉ(Ⅱ )、稀土离子的萃取分离以及稀土荧光配合物方面的研究已有报道[3～ 5] 。为了进一步探讨该类萃取剂的萃取性能 ,在合成萃取剂 1 ,4 双 ( 1′ 苯基 3′ 甲基 5′ 氧代吡唑 4′ 基 )丁二酮 [1 ,4]的基础上 ,研究了Ｈ2 Ａ与ＤＡＭ的氯仿溶液从硝酸介质中协同萃取Ｌｎ(Ⅲ )的性能。通过考察萃取剂浓度和溶液酸度等因素对Ｌｎ(Ⅲ …     

Mixed ligand complexes of β-diketonates: synthesis,characterization, and FAB mass spectral analysis

Complexes of the type MLL′ · nB (where M = Ni(II) and Cu(II); LH and L′H = 2,4-pentanedione (acacH), 1-phenyl-1,3-butanedione (bacH), and 1,3-diphenyl-1,3-propanedione (dbmH); n = 0 to 2 and B = water or pyridine) have been synthesized and characterized. IR spectra are consistent with uninegative bidentate ligands. Magnetic moments and electronic spectral studies reveal high-spin octahedral geometry for nickel(II) complexes and distorted octahedral stereochemistry for copper(II) complexes. Frozen chloroform solution ESR spectra of the copper(II) complexes display significant Jahn–Teller distortion and dimeric behavior of the complexes in solution. FAB mass spectra of the copper(II) complexes also exhibit peaks corresponding to dimers. Molecular, pseudo-molecular, dimeric pseudo-molecular, and fragment ion peaks in unit resolution mass spectra have been identified with the help of their isotope distribution pattern expected due to natural abundances of the ⁶³Cu and ⁶⁵Cu isotopes. All the FAB mass spectral peaks from the fragment ions containing copper have been interpreted on the basis of isotope distribution pattern.     

乙基二茂铁与乙酰丙酸甲酯的缩合反应

以多聚磷酸-浓硫酸-甲醇为催化剂和环已烷为溶剂,由乙基二茂铁与乙酰丙酸甲酯缩合合成4,4-双（乙基二茂铁基）成酸甲酯,转化率73%,产率84%。正交实验法获得的适宜反应条件：乙基二茂铁55mmol,乙酰丙酸甲酯75mmol,浓硫酸3.0mL,环已烷20mL,甲醇11mL。通过元素分析、IR、^1H NMR和^13C NMR确证了缩合产物的结构。     

Reductive mono- and diallylation of the bis(pyridine)dihydropyridyllithium dimer by triallylborane

Reductive allylation of the bis(pyridine)dihydropyridyllithium dimer containing the 1,2- and 1,4-dihydropyridine fragments by triallylborane results mainly in trans- and cis-2,6-diallylpiperidines (60—85%), their ratio depending on the nature of the solvent. The minor reactions products are 2-allyl-1,2,3,6-tetrahydropyridine and 4,10-diallyl-3,9-diazatricyclo[6.2.2.0^2,7]dodecane. The unexpected formation of the latter is due to hetero-Diels—Alder condensation of intermediate products formed in the allylboration of dihydropyridines. The stereochemistry of trans- and cis-2,6-diallylpiperidines was determined from the ¹H and ¹³C NMR spectra of the respective N,N-dimethylpiperidinium iodides. The structure of 4,10-diallyl-3,9-diazatricyclo[6.2.2.0^2,7]dodecane dipicrate was established by X-ray diffraction analysis.     

Synthesis and Characterization of Tetraosmium Carbonyl Complexes Containing a Bridging CO2 Ligand

Treatment of (thd)H (thd=2,2,6,6-tetramethyl-3,5-heptandionate) with excess Os₃(CO)₁₂ in an autoclave at 180°C gives the formation of a brown metal chain complex [Os₂(CO)₅(thd)₂]₂ (1) and a yellow CO₂ cluster complex [Os₄(-H)(-CO₂)(thd)(CO)₁₃] (2) in low yields. Complex 2 was fully identified by a combination of spectroscopic methods and X-ray diffraction study, showing a unique CO₂ ligand bridging a triosmium metal fragment, Os₃(-H)(CO)₁₀ and a monometallic osmium fragment, Os(CO)₃(thd). Upon treatment of 1 with Me₃NO at an elevated temperature, oxidation of the CO ligand occurred at the position trans to the unique CO₂ ligand on the Os(CO)₃(thd) fragment, giving the formation of a second CO₂ cluster [Os₄(-H)(-CO₂)(thd)(CO)₁₂(NCMe)] (3), which is stabilized by a weakly coordinated acetonitrile molecule.     

Bis‐benzimidazolium‐palladium system catalyzed Suzuki‐Miyaura coupling reaction of aryl bromides under mild conditions

Bis‐benzimidazolium salts were prepared successfully from commercially available and inexpensive o‐phenylenediamine through a series of simple reactions. The bis‐NHC‐Pd complexes prepared in situ can catalyze Suzuki‐Miyaura cross‐coupling reaction under very mild conditions in aqueous media with excellent yields. The efficiency of this reaction is demonstrated by its compatibility with a range of functional groups. Di‐ortho‐substituted biaryls could be accomplished in 89–99% yields. Moreover, the rigorous exclusion of air or moisture is not required in these transformations.