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1.
DongHuiYANG ShaoQingCAI YuYingZHAO 《中国化学快报》2003,14(7):720-723
The absolute configuration of rohitukine, isolated from the stem-bark of Dysoxylum binectariferum, was determined to be 5,7-dihydroxy-2-methyl-8-[4-(3S, 4R-3-hydroxy-1-methyl)-piperidinyl]-4H-l-benzopyran-4-one by X-ray crystallographic analysis on the crystal of,4-bromobenzoyl derivatives of rohitukine. At the same time, the modified Mosher method was proved to be unsuitable for determining the absolute configuration of C-3‘ position in rohitukine. 相似文献
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Synthesis,Crystal Structure and Absolute Configuration of (+)-(a-Hydroxybenzyl)phenylphosphinic acid
1 INTRODUCTION a-Hydroxyphosphonic acids and their esters are known to possess broad-based physiological activities and there is close links between biological efficacy and stereochemistry[1~3]. Optical active a-hydroxyphosphonic esters can also serve as useful precursors in organic synthesis[4, 5]. Here we will report the synthesis of optical active a-hydroxyphosphinic acid, (+)-(a-hydroxybenzyl)- phenylphosphinic acid and its crystal structure and the absolute configuration of its a-ca… 相似文献
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Zhi Jie XUE Yuan Chao LI 《中国化学快报》2005,16(12):1569-1572
Polyhydroxy enyne compound (+)-(1'S, 2R, 3S, 5S, 6S)-5,6-dimethoxy-5, 6-dimethyl- 2-(1'-hydroxylpropyl-2-ne)-3-vinyl-l,4-dioxane has been synthesized from D-(-)-tartaric acid. A new chiral center was established by nucleophilic addition with 87% de. The modified Mosher's method was employed to confirm the absolute configuration of 17, which assigned the S-configuration at the new chiral center. 相似文献
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Dr. Keisuke Nishikawa Toshiki Niwa Kento Nishikibe Dr. Momochika Kumagai Prof. Dr. Yoshiki Morimoto 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(43):11045-11049
Feroniellin analogs isolated from Feroniella lucida possess a furanocoumarin skeleton connected to monoterpenic five- to seven-membered ethereal rings by an ether linkage and exhibit a broad spectrum of biological activities. In this contribution, we intended to establish a “ring-size-divergent” synthetic strategy for the monoterpenic five- to seven-membered ethereal rings through the chemical sythesis of feroniellins. The short and comprehensive synthesis of feroniellins was achieved in only two steps from easily available bergamottin based on the “ring-size-divergent” strategy. In addition, these syntheses resulted in revision of the proposed structures for feroniellins A and B and the determination of all the absolute configurations of feroniellins; their preliminary anti-inflammatory activities were investigated as well. 相似文献
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Giovannini PP Fantin G Massi A Venturi V Pedrini P 《Organic & biomolecular chemistry》2011,9(23):8038-8045
An enzymatic strategy for the preparation of optically pure α-alkyl-α,β-dihydroxyketones is reported. Homo- and cross-coupling reactions of α-diketones catalyzed by acetylacetoin synthase (AAS) produce a set of α-alkyl-α-hydroxy-β-diketones (30-60%, ee 67-90%), which in turn are reduced regio-, diastereo-, and enantioselectively to the corresponding chiral α-alkyl-α,β-dihydroxyketones (60-70%, ee >95%) using acetylacetoin reductase (AAR) as catalyst. Both enzymes are obtained from Bacillus licheniformis and used in a crude form. The relative syn stereochemistry of the enantiopure α,β-dihydroxy products is assigned by NOE experiments, whereas their absolute configuration is determined by conversion of the selected 3,4-dihydroxy-3-methyl-pentan-2-one to the natural product (+)-citreodiol. 相似文献
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《Tetrahedron: Asymmetry》2001,12(18):2551-2564
Enantiomerically pure (+)-(αR,α′R)-dimethylmesobilirubin-XIIIα 1 and its (αS,α′S) enantiomer ent-1 were synthesized in ten steps from simple precursors. Resolution was achieved at an early stage in the synthesis, with a racemic monopyrrole precursor rac-6 being converted to its amides 8 with (1S)-camphor-2,10-sultam. Resolution of 8 to 99% d.e. was accomplished in three crystallizations, and the absolute configuration of the acid 6 was deduced by X-ray crystallography of the more crystalline, diastereomerically pure amide 7. Circular dichroism spectroscopy of 1 showed intense bisignate Cotton effects: Δεmax435=+344, Δεmax391=−193 (CHCl3), as expected for a molecular exciton, and consistent with a P-helical intramolecularly hydrogen-bonded ridge-tile conformation. The Cotton effect magnitudes of 1 match almost exactly those found for (−)-(βS,β′S)-dimethylmesobilirubin-XIIIα 11 and (+)-(αR,β′R)-dimethylmesobilirubin-XIIIα. However, the Cotton effect of the pseudo-meso diastereomer (αR,β′S)-dimethylmesobilirubin-XIIIα 12 is not zero. Its large positive exciton couplet and 1H NMR NOE analysis confirm that an α-CH3 exerts a greater steric demand than a β-CH3—by a factor of ∼3. 相似文献
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《Tetrahedron: Asymmetry》1999,10(23):4619-4626
Racemates of cis- and trans-2-(Nβ-t-butoxycarbonyl-Nα-methylhydrazino)cyclopentanols and -cyclohexanols 1–4 were resolved through lipase PS- or Novozym 435-catalysed asymmetric acylation of the secondary OH group at the (R)-stereogenic centre. High enantioselectivity (E >200) was observed when vinyl acetate or vinyl butyrate was used in diisopropyl ether, resulting in the enantiopure hydrazino esters 1a–4a and hydrazino alcohols 1b–4b. Methanolysis of the esters 1a–4a afforded the corresponding 2-hydrazinocycloalkanols 1c–4c (ee usually >95%). 相似文献
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Abstract-Compound 1, the carbocyclic analogue of Ara-T, was synthesized by a four-step synthesis from (+)-(lα,2α,3β,5β)-3-amino-5-(hydroxymethyl)-l,2,-cyclopemane-diol (2), which was prepared from cyclopentadiene via a eight-step route as a potential antiviral agent. 相似文献
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《Tetrahedron: Asymmetry》2000,11(5):1047-1050
(±)-1-Ferrocenylethylamine was resolved by a highly enantioselective acetylation catalyzed by Candida antarctica B lipase. 相似文献
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G. D. Gamalevich A. L. Vlasyuk V. A. Voblikova E. P. Serebryakov 《Russian Chemical Bulletin》2000,49(7):1313-1315
The biologically inactive (+)-enantiomer of 4-(2,6-dimethylheptyl)benzoic acid was converted into the known (R)-3,7-dimethyloctanol withee≥96% by ozonolysis followed by a two-step reduction of the ozonide. This confirmed theR configuration of the starting acid, theS configuration of its biologically active levorotatory antipode, and the absolute configurations assigned to their synthetic
precursors.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1316–1318, July, 2000. 相似文献
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《中国化学快报》1997,(1)
Thesynthesisofopticallyactivecompoundsisanimportantissueinmodemorgan-icchendstry-7-Terpineol,anaturalproductisolatedfrompetitgrainoil,longleafpineoi1andcaeputoill'J,hasbeenasynthetictargetduringthecourseofourstudiesontheasymmetriccatalisedDiels-AlderreactionlvInthispaper,l-phenylsulfOnyl-3-buten-2-one(l)wasusedasthesulfOnyl-functionalizedche1atingenoneforthesynthesischiral2-Terpineol(5)byaasymmetriccata1isedDiels-Alderreaction.TherouteforthesynthesisofopticallyaCtivea-Terpineo1(5)isshownin… 相似文献
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Zusammenfassung Basenkatalysierte Kondensation von 4-Nitrobenzaldehyd mit Dichloracetonitril in Methanol lieferte ein als Methyliminoäther aufgefaßtes Kondensationsprodukt, dessen salzsaure Hydrolyse die im Titel genannte Säure ergab. Sie erwies sich als völlig ident mit einem Präparat, das in einer vorigen Arbeit durch Hydrolyse des 2-[-(4-Nitrophenyl)--oxy-,-dichlormethyl]-oxazolin erhalten wurde. 相似文献
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《Tetrahedron: Asymmetry》2001,12(8):1211-1217
Eight diastereomerically pure epoxides have been prepared from cholest-4-en-3β,6β; -3β,6α-; -3α,6β- and -3α,6α-diols via a combination of steric, protecting group and oxidant effects on stereocontrolled epoxidations of a bis-alicyclic alcohol system within the steroidal skeleton. 相似文献
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Francisc Potmischil Helmut Herzog Joachim Buddrus Mircea D. Gheorghiu 《Monatshefte für Chemie / Chemical Monthly》2000,131(4):345-352
Summary. The stereoselectivities of the quaternization reactions of (4aα,8aβ,9aβ,10aα)- and (4aα,8aα,9aβ,10aα)-tetradecahydro-10-methylacridine
with methyl- and ethyl iodide as well as those of (4aα,8aβ,9aβ,10aα)- and (4aα,8aα,9aβ,10aα)-10-ethyl-tetradecahydroacridine
with methyl iodide were investigated using 13C NMR spectroscopy including 13C-labelling where appropriate. The methylations of both N-methyl amines occur by predominant (60% and 75%, respectively) equatorial
approach, their ethylations occur sterospecifically by equatorial approach, and the methylations of the N-ethyl amines occur
by highly stereoselective (> 90%) axial approach of the quaternizing reagent.
Received October 27, 1999. Accepted November 22, 1999 相似文献
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