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《Tetrahedron letters》1986,27(19):2139-2142
The title compounds of (1R*,3S*) configuration were prepared from 3-formyl-2,2-dimethyl-cyclopropanecarboxylate by addition of CF3CCl2ZnCl, acetylation, and reductive β-elimination with zinc, whereas the (1R*,3R*) isomer was derived from Me2C=CHCH(OH)CCl2CF3 by diazoacetylatlon. Cu(II) catalyzed intramolecular cyclization, and the zinc reduction. 相似文献
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Harding WW Hodge M Wang Z Woolverton WL Parrish D Deschamps JR Prisinzano TE 《Tetrahedron: Asymmetry》2005,16(13):2249-2256
The enantioselective synthesis of the (R,R)- and (S,S)-enantiomers of 1 from commercially available 3-chlorocinnamic acid is reported. The Sharpless asymmetric epoxidation was used to establish the stereocenters in the synthesis of both enantiomers of 1. 相似文献
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Coupled cluster and density functional models of specific rotation and vacuum UV (VUV) absorption and circular dichroism spectra are reported for the conformationally flexible molecules (R)-3-chloro-1-butene and (R)-2-chlorobutane. Coupled cluster length- and modified-velocity-gauge representations of the Rosenfeld optical activity tensor yield significantly different specific rotations for (R)-3-chloro-1-butene, with the latter providing much closer comparison (within 3%) to the available gas-phase experimental data at 355 and 633 nm. Density functional theory overestimates the experimental rotations for (R)-3-chloro-1-butene by approximately 80%. For (R)-2-chlorobutane, on the other hand, all three models give reasonable comparison to experiment. The theoretical specific rotations of the individual conformers of (R)-3-chloro-1-butene are much larger than those of (R)-2-chlorobutane, in disagreement with previous studies of the temperature dependence of the experimental rotations in solution. Simulations of VUV absorption and circular dichroism spectra reveal large differences between the coupled cluster and density functional excitation energies and the rotational strengths. However, while these differences lead to very different specific rotations for (R)-3-chloro-1-butene, they have much less impact on the computed specific rotations for (R)-2-chlorobutane. In addition, the coupled cluster VUV absorption spectrum of (R)-2-chlorobutane compares well to experiment. 相似文献
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Introduction Asarelativelynewmemberofnaturalalkaloidswith2 ,6 disubstituted 3 piperidinolskeleton ,irnigaine 1wasisolatedfromthetubersofArisarumVulgare (Araceae)in1995byMelhaouiandBode .1Itsstructureandrelativeconfigurationswereelucidatedby1HNMRstudiesandtheabsoluteconfigurationwasproposedonthebasisofitsopti calrotation .1Soonafterthen ,Meyerandhisco workersreportedthefirstsynthesisof (- ) (2R ,3R ,6S) irni gaineandtheconfigurationconfirmation .Althoughtheirsynthesisroutewasshortan… 相似文献
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《Tetrahedron: Asymmetry》1998,9(13):2317-2327
Preparation of various heteroaryl propanols 2a–g and of the corresponding propanones 3a–g as starting materials for microbial redox is described. The kinetic resolution of the racemic propanols 2a–g is obtained via oxidation with Pseudomonas paucimobilis and Bacillus stearothermophilus [(R)-alcohols, ee 74–100%]. Similar results are achieved with 3-(2-hydroxypropyl)trifluoromethylbenzene 7 (44%, ee 100% of the (R)-alcohol 6). The reduction of the propanones 3a–d and 3g with baker's yeast and other fungi gives the (S)-alcohols (ee 100%). The pure (S)-alcohols are also obtained by reduction of 1-[3-(trifluoromethyl)phenyl]-2-propanone 7. 1-[(4,4-Dimethyl)-2-(Δ2)oxazolinyl]-2-propanone 3e and 1[2-(Δ2)-thiazolinyl)-2-propanone 3f are not reduced. The heterocyclic rings of (S)-5-(2-hydroxypropyl)-3-methylisoxazole 2d and of (S)-2-(2-hydroxypropyl)-4-methylthiazole 2g are deblocked to the homochiral enamino ketone 8 (78%) and to the protected β-hydroxy aldehyde 9 (73%), respectively. The (R)-3-(2-hydroxypropyl)trifluoromethylbenzene 6 is transfomed into the homochiral precursor of (S)-fenfluramine 10 (overall yield 65%). 相似文献
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Bunnage ME Chippindale AM Davies SG Parkin RM Smith AD Withey JM 《Organic & biomolecular chemistry》2003,1(21):3698-3707
Conjugate addition of lithium dibenzylamide to tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate occurs with high levels of stereocontrol, with preferential addition of lithium dibenzylamide to the face of the cyclic alpha,beta-unsaturated acceptor anti- to the 3-methyl substituent. High levels of enantiorecognition are observed between tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate and an excess of lithium (+/-)-N-benzyl-N-alpha-methylbenzylamide (10 eq.) (E > 140) in their mutual kinetic resolution, while the kinetic resolution of tert-butyl (+/-)-3-methylcyclopentene-1-carboxylate with lithium (S)-N-benzyl-N-alpha-methylbenzylamide proceeds to give, at 51% conversion, tert-butyl (1R,2S,3R,alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-carboxylate consistent with E > 130, and in 39% yield and 99 +/- 0.5% de after purification. Subsequent deprotection by hydrogenolysis and ester hydrolysis gives (1R,2S,3R)-3-methylcispentacin in > 98% de and 98 +/- 1% ee. Selective epimerisation of tert-butyl (1R,2S,3R,alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-carboxylate by treatment with KO'Bu in 'BuOH gives tert-butyl (1S,2S,3R,alphaS)-3-methyl-2-N-benzyl-N-alpha-methylbenzylaminocyclopentane-1-carboxylate in quantitative yield and in > 98% de, with subsequent deprotection by hydrogenolysis and ester hydrolysis giving (1S,2S,3R)-3-methyltranspentacin hydrochloride in > 98% de and 97 +/- 1% ee. 相似文献
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《Tetrahedron: Asymmetry》2001,12(3):369-373
A new preparation of optically active 4-chloro-3-acetoxybutyronitrile (AcBN) was developed using the resting cells of bacteria. The resolution was based on enantioselective hydrolysis of the ester function of the substrate. (R)-AcBN was prepared using Pseudomonas sp. DS-K-717, and the resulting (R)-AcBN was obtained with high enantiomeric excess of >98% with a yield of 36% during the microbial resolution step. (S)-AcBN was prepared in the same manner using the resting cells of Pseudomonas sp. DS-K-19 and showed a high enantiomeric excess of >98% with a yield of 32%. The enzyme activity was enhanced and induced by the addition of AcBN, particularly the (R)-ester hydrolysis, which was enhanced 20-fold. 相似文献
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Wen Xin GU Xiao Bi JING Xiao Chuan CHEN Xin Fu PAN* Department of Chemistry National Laboratory of Applied Organic Chemistry Lanzhou University Lanzhou 《中国化学快报》2001,(3)
Numerous lignans containing 1,4-benzodioxane nucleus represent a class of natural products with cytotoxic and hepatoprotective activities1,2. Recently we have reported the racemic total synthesis of sinaiticin, a flavonolignan of the 1,4-benzodioxane type which was isolated from sinaiticum leaves found in sinai region of Egypt, using 2-(4-hydroxyphenyl)-3-hydroxymethyl-1,4-benzodioxan-6-carbaldehyde as the key interme-diate3,4. This species exhibits significant inhibitory activity against the … 相似文献