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1.
The “naked sugar” (+)-(1R, 4R)-7-oxabicyclo[2.2.1]hept-5-en-one((+)-2) has been converted to D-lividosamine ((+)-1: 3-deoxy-D-glucosamine) and derivatives via (+)-2-chloro-2,3-dideoxy-5,6-O-isopropylidene-D-arabino-hexono-1,4-lactone ((+)-33) and (+)-2-azido-2,3-dideoxy-5,6-O-isopropylidene-D-ribo-hexono-1,4-lactone ((+)-34) in a highly stereoselective fashion. Similarly, 2-acetamido-2,3-dideoxy-D-arabino-hexose and derivatives were derived from the “naked sugar” (−)-(1S,4S-7-oxabicyclo[2.2.1]-hept-5-en-2-one ((−)-2) via the double hydroxylation of the C=C double bond in (−)-N-benzyl-N-[(1R,2S,4S)-6-bromo-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl] amine ((−)-40). 相似文献
2.
Elisabetta Brenna Claudio Fuganti Daniela Fuganti Piero Grasselli Luciana Malpezzi Giuseppe Pedrocchi-Fantoni 《Tetrahedron》1997,53(52):5195-17780
(+)- and (−)-etodolac enantiomers were prepared both by classical resolution via crystallisation of diastereoisomeric salts with (+) and (−)--methylbenzylamine, and by suitable manipulation of derivatives (−)-3- and (+)-4, obtained by lipase-catalysed kinetic resolution of racemic 3 X-ray diffraction analysis of the 4-bromobenzoate derivative of (+)-3, obtained from enantiopure acetate (+)-4, allowed us to determine the absolute (R) configuration of (−)-etodolac. 相似文献
3.
(1S,4S)-7-Oxabicyclo[2.2.1]hept-5-en-2-one ((−)-5, a “naked sugar”) has been converted to (−)-(1R,4S,6S)-6-endo-benzyloxy-2-bromo-7-oxabicyclo[2.2.1]hept-2-ene ((−)-12) in a highly stereoselective fashion. Double hydroxylation of the C=C double bond of (−)-12, followed by acetylation and Baeyer-Villiger oxidation of the resulting -acetoxyketone (−)-14 afforded (−)-5-O-acetyl-2-O-benzyl-3-deoxy-β-D-arabino-hexofuranurono-6,1-lactone ((−)-15). This compound was converted readily into (+)-methyl 3-deoxy--D-arabino-hexofuranoside ((+)-6 and (+)-methyl 3-deoxy-β-L-xylo-hexofuranoside ((+)-7) and partially protected derivatives. (−)-15 was also converted into 4-deoxy-D-lyxo-hexopyranose (34) and several partially protected derivatives such as (+)-methyl 4-deoxy-2,3-O-isopropylidene--D-lyxo-hexopyranoside ((+)-8). 相似文献
4.
Katharina Fritzsche Barbara Dogan Hans-Dieter Beckhaus Christoph Rüchardt 《Thermochimica Acta》1990,160(2):147-159
The heats of combustion of 1-nitroadamantane (1), 2-nitroadamantane (2), 2,2-di-nitroadamantane (3) and 2-cyano-2-nitroadamantane (4) were measured by combustion calorimetry, and the heats of sublimation were derived from the temperature dependence of the vapour pressure measured in a flow system. The results for ΔHXXXc(c) and ΔHSub (in kJ mol−1, standard deviation in parentheses) are: 1, −5824.1 (±2.2) and 63.6 (±1.0); 2, −5841.0 (±2.2) and 58.0 (±2.3); 3, −5685.2 (±1.0) and 96.4 (±1.4); 4, −6238.4 (±1.5) and 70.0 (±1.9).
A comparison of the resulting heats of formation ΔHXXXf(g) (in kJ mol−1, standard deviation in parentheses) for 1 = −191.1 (± 2.4), 2 = −179.8 (±3.2), 3 = −154.3 (±1.7) and 4 = −21.0 (±2.5) reveals a destabilizing interaction of the geminal substituents in 3 and 4 amounting to 59 kJ mol−1 (nitro/nitro) and 33 kJ mol−1 (nitro/cyano) respectively. 相似文献
5.
The C-12˜C-17 segment
of (+)-aplasmomycin (
) was synthesized stereoselectively starting from (−)-malic acid based on the stereoselective ketone reduction. 相似文献
6.
Medium-resolution spectra of the N2 b1Πu-X1Σg+ band system were recorded by 1 + 1 multiphoton ionization. In the spectra we found different linewidths for transitions to different vibrational levels in the b 1Πu state: Δν0 = 0.50 ± 0.05 cm−1, Δν1 = 0.28 ± 0.02 cm−1, Δν2 = 0.65 ± 0.06 cm−1, Δν3 = 3.2 ± 0.5 cm−1, Δν4 = 0.60 ± 0.07 cm−1, and Δν5 = 0.28 ± 0.02 cm−1. From these linewidths, predissociation lifetimes τν were obtained: τ0 = 16 ± 3 ps, τ1 > 150 ps, τ2 = 10 ± 2 ps, τ3 = 1.6 ± 0.3 ps, τ4 = 9 ± 2 ps, and τ5 > 150 ps. Band origins and rotational constants for the b 1Πuν = 0 and 1 levels were determined for the 14N2 and 14N15N molecules. 相似文献
7.
Takahiro Hosokawa Takanori Kono Toru Shinohara Shun-Ichi Murahashi 《Journal of organometallic chemistry》1989,370(1-3):C13-C16
The oxidative cyclization of 2-(3-pentenyl)phenol catalyzed by [(η3-pinene)PdOAc]2 gives optically active (+)-2-vinylchroman (25% e.e.), while (−)-2-(1-hydroxyethyl)chroman (56% e.e.) is formed as a single diastereomer upon treatment with t-BuOOH in the presence of Ti(OiPr)4 and
-(+)-diethyl tartrate. 2-(2-Butenyl)phenol also undergoes the Ti-promoted asymmetric cyclization to give (2S,1′R)-(−)-2-(1-hydroxyethyl)-2,3-dihydrobenzofuran (29% e.e.). 相似文献
8.
A spectrofluorimetric method to determine levofloxacin is proposed and applied to determine the substance in tablets and spiked human urine and serum. The fluorimetric method allow the determination of 20–3000 ng ml−1 of levofloxacin in aqueous solution containing acetic acid–sodium acetate buffer (pH 4) with λexc=292 and λem=494 nm, respectively. Micelle enhanced fluorescence improves the sensibility and allows levofloxacin direct measurement in spiked Human serum (5 μg ml−1) and urine (420 μg ml−1), in 8 mM sodium dodecyl sulphate solutions at pH 5. 相似文献
9.
The “naked sugar” (+)-(1R,2R,4R)-2-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl acetate ((+)-3) was converted in ten synthetic steps into the new C-nucleoside (1R)-1-C-(6′-amino-7′H-purin-8′-yl)-1,4-anhydro-3-azido-2,3-dideoxy- D-erythro-pentitol ((+)-2) in 19% overall yield. 相似文献
10.
J zsef Kaizer R bert Csonka G bor Speier 《Journal of molecular catalysis. A, Chemical》2002,180(1-2):91-96
The oxidation reaction of 2-aminophenol (OAP) to 2-aminophenoxazin-3-one (APX) initiated by 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) has been investigated in methanol at ambient temperature. The oxidation of OAP was followed by electronic spectroscopy and the rate constants were determined according to the rate law −d[OAP]/dt=kobs[OAP][TEMPO]. The rate constant, activation enthalpy and entropy at 298 K are as follows: kobs (dm3 mol−1 s−1)=(1.49±0.02)×10−4, Ea=18±5 kJ mol−1, ΔH‡=15±4 kJ mol−1, ΔS‡=−82±17 J mol−1 K−1. The results of oxidation of OAP show that the formation of 2-aminophenoxyl radical is the key step in the activation process of the substrate. 相似文献
11.
Polarized absorption spectra of Ba(MnO4)2·3H2O/Ba(ClO4)2·3H2O mixed single crystals are reported at 4.2°K. Previous 1T2 → 1A1 assignments for the 5200 Å and 3000 Å absorption bands of MnO4− are substantiated; further support is provided for the 1T1 → 1A1 assignment of the 3600 Å absorption band of MnO4−. The site-splitting of the 5200 Å 1T2 state is E(1E)−E(1A) ≈ −150 cm−1; that of the 3000 Å 1T2 state is E(1E)−E(1A) ≈ 300 cm−1. A significant e vibronic intensity component is observed in the 5200 Å 1T2 state. 相似文献
12.
Flow injection (FI) and sequential injection (SI) systems with anodic stripping voltammetric detection have been exploited for simultaneous determination of some metals. A pre-plated mercury film on a glassy carbon disc electrode was used as a working electrode in both systems. The same film can be repeatedly applied for at least 50 analysis cycles, thus reducing the mercury consumption and waste. A single line FI voltammetric system using an acetate buffer as a carrier and an electrolyte solution was employed. An injected standard/sample zone was mixed with the buffer in a mixing coil before entering a flow cell. Metal ions were deposited on the working electrode by applying a potential of −1.1 V vs Ag/AgCl reference electrode. The stripping was performed by anodically scanning potential of working electrode to +0.25 V, resulting a voltammogram. Effects of acetate buffer concentration, flow rate and sample volume were investigated. Under the selected condition, detection limits of 1 μg l−1 for Cd(II), 18 μg l−1 for Cu(II), 2 μg l−1 for Pb(II) and 17 μg l−1 for Zn(II) with precisions of 2–5% (n=11) were obtained. The SI voltammetric system was similar to the FI system and using an acetate buffer as a carrier solution. The SI system was operated by a PC via in-house written software and employing an autotitrator as a syringe pump. Standard/sample was aspirated and the zone was then sent to a flow cell for measurement. Detection limits for Cd(II), Cu(II), Pb(II) and Zn(II) were 6, 3, 10 and 470 μg l−1, respectively. Applications to water samples were demonstrated. A homemade UV-digester was used for removing organic matters in the wastewater samples prior to analysis by the proposed voltammetric systems. 相似文献
13.
Johannes C. S. Malan Jacobus A. Steenkamp Desmond A. Young Daneel Ferreira 《Tetrahedron》1989,45(24):7859-7868
Acid-catalyzed condensation of (+)-mollisacacidin-[(2R, 3S, 4R)-2, 3-trans-3, 4-trans-flavan-3,3′,4,4′,7-pentaol] with an excess of (−)-robinetinidol[(2R,3S)-2,3-trans-flavan-3,3′,4′,5′,7-pentaol] afforded a novel series of bi-, tri-, and tetraflavanoid profisetinidins. They are accompanied by (−)-fisetinidol-(4,2′)-(−)-robinetinidol which results from the pyrogallol B-ring of (−)-robinetinidol serving as nucleophile competing with its resorcinol A-ring in coupling with a C-4 carbocationic intermediate. Similar condensation with (+)-epifisetinidol[(2S,3S)-2,3-cis-flavan-3,3′,4′,7-tetraol] led to the exclusive formation of [4,6]-interflavanyl bonds, these units being ‘linearly’ arranged in the tetraflavanoid analogue in contrast to the ‘branched’ nature of the (−)-robinetinidol homologue. 相似文献
14.
Pelayo Camps Diego Muoz-Torrero Jordi Rull Merc Font-Bardia Xavier Solans 《Tetrahedron: Asymmetry》2007,18(24):2947-2958
An enantiodivergent preparation of (+)-(R)- and (−)-(S)-3-amino-4,4-dimethyl-1-phenylpyrrolidin-2-one, (R)- and (S)-9, and several derivatives, from 4,4-dimethyl-1-phenylpyrrolidin-2,3-dione, 4, and (R)- or (S)-1-phenylethylamine, (R)- or (S)-5, as the chirality transfer agents, is described. Amine (S)-9 has also been used as a chiral auxiliary in a diastereoselective Michael reaction. 相似文献
15.
The spectrum of CD2HF was measured by high-resolution interferometric Fourier-transform IR (FTIR) spectroscopy (apodised instrumental band with:0.004 cm−1 fwhm) between 800 and 1200 cm−1 covering the four lowest fundamentals. A complete rotational analysis using a semi-automatic assignment procedure yields accurate band centres (ν9: 912.2028 cm−1, ν6:964.4994 cm−1, ν5: 1050.5104 cm−1, ν4: 1093.8632 cm−1) and a complete set of first-order Coriolis coupling constants. The most important couplings occur between ν9 and ν6 (ξa= 1.069 cm−1, ξc= −0.3535 cm−1) and between ν5 and ν4 (ξb= −0.80606 cm−1). The analysis was guided by and compared with results from our ab initio calculations for Coriolis constants and transition moments using CADPAC at TZP/MP2 level. 相似文献
16.
Mireille Attolini Gilles Iacazio Gilbert Peiffer Michel Maffei 《Tetrahedron: Asymmetry》2003,14(24):3857-3860
Enzymatic resolution of racemic 3-bromo-cyclohept-2-enol 2 with lipozyme affords enantiomerically pure (S)-(−)-2 whose absolute configuration was determined by chemical correlation, and further allowed an enantioselective synthesis of (S)-(+)-diethyl (3-hydroxy-cyclohept-1-enyl)phosphonate 1. 相似文献
17.
Total syntheses of (−)-plectrodorine [(−)-1] and (+)-oxerine [(+)-3] possessing the cyclopenta[c]pyridine ring system have been accomplished through a route starting from the chiral γ-butyrolactone 7 and exploiting the intramolecular oxazole–olefin Diels–Alder reaction. The sign of specific rotation for the synthetic (+)-3 was in disagreement with that reported for natural oxerine, leaving the absolute configuration of this monoterpene alkaloid incomplete. 相似文献
18.
The cycloheptano-isoxazoline 1, prepared from D-glucose, is converted to 6,7-dideoxy cycloheptitols which are suitable precursors for the synthesis of enantiomerically pure (+) and (−)-Calystegines B2. 相似文献
19.
Asymmetric hydroboration of [E]- and [Z]-2-methoxy-2-butene, using (−)-diisopinocampheylborane at −25°C in THF solvent, followed by oxidation using H2O2/NaOH, gave (−)-[2R,3R]- and (+)-[2R,3S]-3-methoxy-2-butanols in >97 and 90% ee, respectively. (−)-[2R,3R]-3-Methoxy-2-butanol was converted to (−)-[2R,3R]-butane-2,3-diol (>97% ee, in an overall yield of 65%). 相似文献
20.
Christopher Glidewell S. Zaka Ahmed Michael Gottfried Philip Lightfoot Brodyck J.L. Royles Jeremy P. Scott Jrg Wonnemann 《Journal of organometallic chemistry》1997,530(1-2):177-185
Ferrocenyl-1,2-diketones FcCOCOR, 3, [Fc = (C5H5)Fe(C5H4)] can be prepared by oxidation of acylferrocenes FcCOCH2R or, more efficiently, by oxidation of the isomeric ketones FcCH2COR, 2. The ketones 2 are in turn readily synthesized from the salt (FcCH2PPh3)+I− via the acylated salts [FcCH(COR)PPh3]+I−. The haloacylferocenes FcCOCClx H3−x (x = 1, 2, 3, of which the x = 2 example is synthetically equivalent to a diketone) are synthesized by Friedel—Crafts acylation of ferrocene using CClxH3−xCOCl/AlCl3, but the reaction proceeds via two parallel pathways, one giving the normal acyl derivatives FcCOCClxH3−x and the other giving the reduced products FcCOCClx−1H4−x. Two diketones FcCOCOFc 3b and FcCOCOC6H4Ph 3c have been structurally characterised by single-crystal X-ray diffraction. 相似文献