Preparation,molecular structures,and characteristic properties of (E)-1-(2-furyl)- and (E)-1-(2-thienyl)-2-(3-guaiazulenyl)ethylenes and (E)-1-(3-furyl)- and (E)-1-(3-thienyl)-2-(3-guaiazulenyl)ethylenes

Wittig reactions of 2-furaldehyde (20) [and thiophene-2-carbaldehyde (21)] with (3-guaiazulenylmethyl)triphenylphosphonium bromide (19) in ethanol containing NaOEt at 25 °C for 24 h under argon give (E)-1-(2-furyl)-2-(3-guaiazulenyl)ethylene (22E) and (E)-1-(2-thienyl)-2-(3-guaiazulenyl)ethylene (23E) in 53 and 36% yields. Similarly, Wittig reactions of 3-furaldehyde (29) [and thiophene-3-carbaldehyde (30)] with 19 under the same reaction conditions as for 20 and 21 afford (E)-1-(3-furyl)-2-(3-guaiazulenyl)ethylene (31E) and (E)-1-(3-thienyl)-2-(3-guaiazulenyl)ethylene (32E) in 32 and 46% yields. Molecular structures and characteristic properties as well as preparation of the title E (i.e., one of the geometrical isomers) forms, with a view to comparative study, are reported. Moreover, reactions of those conjugated π-electron systems with TCNE (=tetracyanoethylene) in benzene [and in DMF (=N,N-dimethylformamide)] at 25 °C for 24 h under argon yield unique products, possessing interesting molecular structures, respectively, whose characteristic properties and crystal structures are documented, also.     

Smectic A and smectic C materials: partially deuteriated chiral liquid crystals (S)-(-)-2-methylbuty 4-(4-(d13)-hexyloxyphenyl)benzoate and (S)-(-)-2-methylbutyl 4-(4-(d17)-octyloxyphenyl)benzoate

In order to study the difference in microscopic orientation of ferro- and antiferroelectric liquid crystalline molecules, we synthesized the partially deuteriated chiral compounds, (S)-(^-)-2-methylbutyl 4-(4-(d₁₃)-hexyloxy- and (S)-(^-)-2-methylbutyl 4-(4-(d₁₇)-octyloxy-phenyl)benzoates. Fundamental physical properties such as phase transition temperatures, spontaneous polarization and tilt angle were determined. Polarized FTIR measurements were also made to provide information on molecular structure and orientation.     

Total synthesis of (S)-(+)-curcudiol, and (S)-(+)- and (R)-(-)-curcuphenol.

A highly enantioselective synthesis of the versatile chiral synthons possessing one stereogenic center, (S)- and (R)-4-aryl-5-hydroxy-(2E)-pentenoate (3) was achieved based on the enzymatic reaction of (+/-)-3 with commercially available lipases MY-30 or OF-360 from Candida rugosa. Application of (S)-3 and (R)-3 to the total syntheses of(S)-curcuphenol (1), (S)-curcudiol (2), and (R)-curcuphenol (1), respectively, is described.     

Smectic A and smectic C materials: partially deuteriated chiral liquid crystals (S)-(-)-2-methylbuty 4-(4-(d13)-hexyloxyphenyl)benzoate and (S)-(-)-2-methylbutyl 4-(4-(d17)-octyloxyphenyl)benzoate

In order to study the difference in microscopic orientation of ferro- and antiferroelectric liquid crystalline molecules, we synthesized the partially deuteriated chiral compounds, (S)-(^-)-2-methylbutyl 4-(4-(d₁₃)-hexyloxy- and (S)-(^-)-2-methylbutyl 4-(4-(d₁₇)-octyloxy-phenyl)benzoates. Fundamental physical properties such as phase transition temperatures, spontaneous polarization and tilt angle were determined. Polarized FTIR measurements were also made to provide information on molecular structure and orientation.     

Synthesis of (-)-7-epiaustraline and (-)-1-epicastanospermine

Highly efficient and selective syntheses of the title compounds are described. The cornerstone of the synthetic plan is the tandem inter [4 + 2]/inter [3 + 2] cycloaddition process. These syntheses differ from previous applications of this strategy in that they incorporate an alkylation in the hydrogenolysis step to close the second ring of the azabicyclic systems. Notable features of the sequence are (1) the highly regio- and stereoselective [3 + 2] cycloaddition of nitronate 15 with siloxymethyl (Z)-beta-silylvinyl ketone (Z)-22b and (2) the highly selective reduction of the resulting ketone 24a with L-Selectride. A single-crystal X-ray structure analysis of synthetic (-)-7-epiaustraline confirmed that the targeted structure was successfully synthesized. This stimulated a reexamination of the structural assignment of the natural product. (-)-1-Epicastanospermine was synthesized in four steps from the common intermediate 27a. The absolute configuration of (-)-1-epicastanospermine was assured by single-crystal X-ray structure analysis of intermediate (-)-27a. Thus, the sign of the optical rotation had to be revised. The overall efficiency of these syntheses were 9 steps and 23% yield for (-)-7-epiaustraline and 10 steps and 20% yield for (-)-1-epicastanospermine     

Total syntheses of beta-carboline alkaloids, (R)-(-)-pyridindolol K1, (R)-(-)-pyridindolol K2, and (R)-(-)-pyridindolol.

The total syntheses of beta-carboline alkaloids, (R)-(-)-pyridindolols (1, 5, and 6) are described. The two key steps involved are (1) a thermal electrocyclic reaction of the 3-alkenylindole-2-aldoxime 10 and (2) a thermal cyclization of 3-alkynylindole-2-aldoxime 11 to construct the beta-carboline N-oxides 8, which upon heating with acetic anhydride and sequential treatment with trifluoromethanesulfonic anhydride gave the triflates 18. The Stille coupling reaction of 18 with vinylstannane, followed by cleavage of MOM ether, afforded the 1-ethenyl-3-hydroxymethyl-beta-carboline (7a). Subsequent acetylation of 7a yielded the acetate 7b, which was subjected to the Sharpless asymmetric 1,2-dihydroxylation by AD-mix-beta to produce (R)-(-)-pyridindolol K2 (6). Selective acetylation of 6 was effected by Ac(2)O and collidine to form (R)-(-)-pyridindolol K1 (5). By contrast, hydrolysis of 6 provided (R)-(-)-pyridindolol (1).     

Molecular rearrangements of (-)-modhephene and (-)-isocomene to a (-)-triquinane

The preparation and further rearrangement of (-)-modhephene (1) to a (-)-triquinane 5 has been assessed through acid catalysis. The rearrangement involved protonation, 1,2 sigma-bond and methyl shifts, and deprotonation. Monitored experiments by 1H NMR spectroscopy suggested the intermediate (-)-isocomene (3), which was further evidenced when a sample of natural (-)-3 undergoes acid-catalyzed conversion to the (-)-triquinane 5. In addition, deuterated (-)-modhephene (1-d) labeled stereospecifically at the 14beta geminal methyl group at C4 was synthesized, through the corresponding chiral deuterated primary alcohol, in 5 steps, starting from natural (-)-14-hydroxymodhephene (8), and rearranged under acid catalysis to elucidate the stereochemical factors that control the methyl shift at this position. The final deuterium-labeled (-)-triquinane, 5-d, obtained from [14-(2)H1]-1-d was established to have deuterium in the methyl group at C5 by 13C NMR spectroscopy. This stereoselective methyl migration is in accordance with the molecular orbital demand formulated by the quantum chemical calculations performed in the present study.     

Novel (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles from (E)- and (Z)-3-styrylchromones: the unexpected case of (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles

An efficient synthetic method for the preparation of (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles has been developed. The reaction of (E)- and (Z)-3-styrylchromones with hydrazine hydrate afforded the corresponding (E)- and (Z)-4-styrylpyrazoles, respectively, saved 4′-nitro-derivatives where both (E)- and (Z)-4′-nitro-3-styrylchromones afforded (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles. The reaction mechanism for these transformations was discussed and the stereochemistry of all products was assigned by NMR experiments.     

1-(Triorganylsilyl)-2-(triethoxysilyl)ethanes

Conclusions The conditions were found for the hydrosilylation of CH₂=CHSi(OC₂H₅)₃ with triorganylsilanes in the presence of H₂PtCl₆ · 6H₂O in isopropanol, which assured a high yield (>90%) of the 1-(triorganylsilyl)-2-(tri-ethoxysilyl)ethanes. These conditions were used to synthesize 27 new 1-(triorganylsilyl)-2-(triethoxysilyl)-ethanes.The addition of (C₂H₅O)₃SiH to (CH₂=CHSi(CH₃)₃ in the presence of the same catalyst gave 1-(trimethyl-silyl)-2-(triethoxysilyl)ethane in 98.6% yield.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1622–1625, July, 1976.     

Reaction of (R)-(-)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato)platinum( II) with guanosine

The reaction of a new antitumor platinum complex, (R)-(-)-2-aminomethylpyrrolidine(1,1-cyclobutanedicarboxylato++ +)platinum(II) (1) with guanosine at room temperature in an aqueous solution was followed by proton nuclear magnetic resonance (1H-NMR) spectroscopy and high performance liquid chromatography (HPLC) at intervals. Both techniques showed that a new compound was formed by displacement of the 1,1-cyclobutanedicarboxylate moiety of 1 with two guanosines, and its 1H-NMR spectrum and HPLC chromatogram were proved to be identical with those of [(R)-(-)-2-aminomethylpyrrolidine]bis(N7-guanosine)platinum(II) (2), which was obtained upon successive treatment of (R)-(-)-2-aminomethylpyrrolidinedichloroplatinum(II) (3) with AgNO3 and 2 mol eq of guanosine in water. The binding sites of the platinum to the two guanosine moieties in 2 were confirmed by the pH dependence of the two G-H8 signals.     

Enantiocontrolled synthesis of (-)-9-epi-pentazocine and (-)-aphanorphine

We have developed novel asymmetric routes to (-)-9- epi-pentazocine and (-)-aphanorphine from a d-tyrosine derivative. The tricyclic frameworks of (-)-9- epi-pentazocine and (-)-aphanorphine were assembled stereoselectively via intramolecular Friedel-Crafts reaction of the corresponding bicyclic precursors, generated with titanium-promoted enyne cyclization and indium-initiated atom-transfer radical cyclization, respectively.     

OH(3) (-) and O(2)H(5) (-) double Rydberg anions: predictions and comparisons with NH(4) (-) and N(2)H(7) (-)

A low barrier in the reaction pathway between the double Rydberg isomer of OH(3) (-) and a hydride-water complex indicates that the former species is more difficult to isolate and characterize through anion photoelectron spectroscopy than the well known double Rydberg anion (DRA), tetrahedral NH(4) (-). Electron propagator calculations of vertical electron detachment energies (VEDEs) and isosurface plots of the electron localization function disclose that the transition state's electronic structure more closely resembles that of the DRA than that of the hydride-water complex. Possible stabilization of the OH(3) (-) DRA through hydrogen bonding or ion-dipole interactions is examined through calculations on O(2)H(5) (-) species. Three O(2)H(5) (-) minima with H(-)(H(2)O)(2), hydrogen-bridged, and DRA-molecule structures resemble previously discovered N(2)H(7) (-) species and have well separated VEDEs that may be observable in anion photoelectron spectra.     

An Efficient Synthesis of Optically Pure (R)- and (S)-2-(aminomethyl)alanine ((R)- and (S)-ama) and (R)- and (S)-2-(aminomethyl)leucine ((R)- and (S)-aml)

An efficient synthesis of enantiomerically pure (R)- and (S)-2-(aminomethyl)alanine ((R)- and (S)-Ama) 1a and (R)- and (S)-2-(aminomethyl)leucine ((R)- and (S)-Aml) 1b is described (Schemes 1 and 2). Resolution of the racemic amino acids was achieved using L -phenylalanine cyclohexylamide ( 2 ) as chiral auxiliary. The free amino acids 1a, b were converted to the N^α-Boc,N^γ-Z-protected derivatives 11a, b (Scheme 3) ready for incorporation into peptides. Based on the three crystal structures of the diastereoisomeric peptides 8a, 8b , and 9b , the absolute configurations in both series were determined. β-Turn type-I geometries were observed for structures 8b and 9b , whereas 8a crystallized in an extended backbone conformation.     

Straightforward synthesis of (R)-(-)-kjellmanianone

A direct route to enantiomerically pure (-)-kjellmanianone is reported. The synthesis involves a cerium-catalyzed alpha-hydroxylation and an enzyme-catalyzed procedure to resolve tertiary alcohols at key stages. The intermediate beta-oxo ester was alpha-hydroxylated to give good yields of racemic kjellmanianone. The resolution of the racemic material was achieved by enzymatic saponification, followed by a chemical decarboxylation sequence to give enantiopure (-)-kjellmanianone with 99 % ee. Bromination then afforded the (-)-bromo derivative, whose X-ray structure provided evidence for the R configuration of (-)-kjellmanianone.     

Asymmetric syntheses of the homalium alkaloids (-)-(s,s)-homaline and (-)-(r,r)-hopromine

The highly diastereoselective conjugate additions of the novel lithium amide reagents lithium (R)-N-(3-chloropropyl)-N-(α-methylbenzyl)amide and lithium (R)-N-(3-chloropropyl)-N-(α-methyl-p-methoxybenzyl)amide to α,β-unsaturated esters were used as the key steps in syntheses of the homalium alkaloids (-)-(S,S)-homaline and (-)-(R,R)-hopromine. The asymmetric synthesis of (-)-(S,S)-homaline was achieved in 8 steps and 18% overall yield, and the asymmetric synthesis of (-)-(R,R)-hopromine was achieved in 9 steps and 23% overall yield, from commercially available starting materials in each case. These syntheses therefore represent by far the most efficient total asymmetric syntheses of these alkaloids reported to date. A sample of the (4'R,4'S)-epimer of hopromine was also produced using this approach, which provided the first unambiguous confirmation of its absolute configuration and therefore that of natural (-)-(R,R)-hopromine.     

Photoelectron spectroscopy and density functional theory study of TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3) clusters

Small titanium-aluminum oxide clusters, TiAlO(y) (-) (y=1-3) and TiAl(2)O(y) (-) (y=2-3), were studied by using anion photoelectron spectroscopy. The adiabatic detachment energies of TiAlO(y) (-) (y=1-3) were estimated to be 1.11±0.05, 1.70±0.08, and 2.47±0.08eV based on their photoelectron spectra; those of TiAl(2)O(2) (-) and TiAl(2)O(3) (-) were estimated to be 1.17±0.08 and 2.2±0.1eV, respectively. The structures of these clusters were determined by comparison of density functional calculations with the experimental results. The structure of TiAlO(-) is nearly linear with the O atom in the middle. That of TiAlO(2) (-) is a kite-shaped structure. TiAlO(3) (-) has a kite-shaped TiAlO(2) unit with the third O atom attaching to the Ti atom. TiAl(2)O(2) (-) has two nearly degenerate Al-O-Ti-O-Al chain structures that can be considered as cis and trans forms. TiAl(2)O(3) (-) has two low-lying isomers, kite structure and book structure. The structures of these clusters indicate that the Ti atom tends to bind to more O atoms.     

Synthesis of (E)- and (Z)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles

Abstract  

An efficient synthesis method for the preparation of a series of new (Z)- and (E)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles was developed. The reaction of (Z)- and (E)-3-styrylchromones with hydrazine hydrate afforded the corresponding (Z)- and (E)-3(5)-(2-hydroxyphenyl)-4-styrylpyrazoles, except for nitro derivatives, where both (Z)- and (E)-4′-nitro-3-styrylchromones afforded (E)-3(5)-(2-hydroxyphenyl)-4-(4-nitrostyryl)pyrazoles. The reaction mechanism for these transformations is discussed and the stereochemistries of all products were established by NMR experiments.     

An equilibrium analysis of the aqueous H+-MoO4(2-)-(HP)O(3)2- and H+-MoO4(2-)-(HP)O(3)2--HPO4(2-) systems

The speciation in the phosphitomolybdate system, H+-MoO4(2-)-(HP)O(3)2-, has been determined from combined potentiometric and 31P NMR measurements in 0.600 M Na(Cl) medium at 298(1) K. Potentiometric titration data were collected in the ranges 2.5<-log[H+]<6.2, 40.0相似文献   

Determination of (S)-(-)-cathinone and its metabolites (R,S)-(-)-norephedrine and (R,R)-(-)-norpseudoephedrine in urine by high-performance liquid chromatography with photodiode-array detection.

A high-performance liquid chromatographic (HPLC) procedure with photodiode-array detection (DAD) is described for the determination of (S)-(-)-cathinone (S-CA) and its metabolites (R,S)-(-)-norephedrine (R-NE) and (R,R)-(-)-norpseudoephedrine (R-NPE) in urine. Extraction and clean-up of 1-ml urine samples were performed on a cyano-bonded solid-phase column using (+/-)-amphetamine as internal standard. The concentrated extracts were separated on a 3-microns ODS-1 column with acetonitrile-water-phosphoric acid-hexylamine as the mobile phase. Peak detection was done at 192 nm. The detection limits for S-CA and R-NE/R-NPE in urine were 50 and 25 ng/ml, respectively. The differentiation of the enantiomers of cathinone and norephedrine was achieved by derivatization with (S)-(-)-1-phenylethyl isocyanate to the corresponding diastereomers followed by HPLC-DAD on a 5-microns normal-phase column. The R and S enantiomers of norpseudoephedrine were determined by gas chromatography-mass spectrometry after on-column derivatization with (S)-(-)-N-trifluoroacetylprolyl chloride. Following a single oral dose of 0.5 mg/kg of S-CA, the concentrations found in urine ranged from 0.2 to 3.8 micrograms/ml of S-CA, from 7.2 to 46.0 micrograms/ml of R-NE and from 0.5 to 2.5 micrograms/ml of R-NPE.