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1.
《Tetrahedron: Asymmetry》1999,10(6):1033-1039
The synthesis of four new derivatives of cis-hydroxy-cis-dihydropinol with allyl-, epoxyalkyl-, hydroxyalkyl- and ketoalkyl-groups substituted on the cyclohexane ring is presented. The cis-orientation of hydroxyl group at C-2 and the configuration of all stereogenic centers is confirmed by X-ray crystallography. 相似文献
2.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1993,49(8):1109-1119
The reaction of ethyl mercaptoacetate with some 3-aryliden-4-chromanones yields the corresponding ethyl 3-aryl-9b-hydroxy-1,3,3a,9b-tetrahydro-4H-thieno[3,4-c]benzo[e]pyrane-1-carboxylates. In spite of the presence of four chirality centers, the reaction is diastereospecific and gives a single diastereoisomer whose configuration and conformation were specified by its PMR data.The cis-fused tetrahydrothiophenic and dihydropyranic cycles lie in half-chair conformation. The 9b-hydroxyl and the 3-aryl groups are in a cis equatorial and pseudoequatorial disposition. The ester group, also cis with the hydroxyl group, presents a hydrogen bond with the hydroxyl. In the presence of an ortho-substituent at the phenyl group (particularly a chlorine atom), this phenyl group undergoes a notable rotation as is pointed out by a radiocristallographic study. A comparative study between the NMR and radiocristallographic data allows the confirmation of the maintenance of the same conformation in solid and dissolved states. 相似文献
3.
2,3-Dialkyl-1,4-cyclopentanediols are obtained by lithium-liquidammonia-alcohol reduction of 2,3-dialkyl-4-hydroxy-2-cyclopentenones. The configuration of the diastereoisomers formed was proved by 1H-NMR spectroscopy and by chemical evidence. In the most abundant isomer the alkyl groups are trans and each is in trans position to the vicinal hydroxyl function. In another diastereoisomer formed in substantial amount the alkyl groups have a cis orientation and are trans to the vicinal hydroxyl function. The 1H-NMR parameters found are more useful generally for configurational assignments to synthetic and modified prostaglandins. 相似文献
4.
Magalie ColletMichel Baltas Alexandre MartinezCécile Dehoux-Baudoin Liliane Gorrichon 《Tetrahedron letters》2003,44(9):1891-1894
The aldolisation reaction of lithium ethyl fluoroacetate with cis and trans α,β-epoxyaldehydes in their racemic forms proceeds with good C3-OH diastereoselectivity and much less at the C2-F carbon atom. A two-step reaction on the major aldol compounds (iodination, lactonisation) led to racemic functionalised C2 fluorinated lactones, possessing a C2/C3cis relationship between the fluorine and hydroxyl groups. 相似文献
5.
Hongbin Sun 《Tetrahedron》2005,61(44):10462-10469
Compounds that simultaneously combine charge and conformational features of glycosyltransfer transition states are of interest as transition state analog inhibitors. The synthesis of a central intermediate, cis-3a,6-dihydroxy-hexahydro-cyclopenta[b]pyrrol-2-one, which yielded a family of substituted cis-3a,6-dihydroxy-hexahydro-cyclopenta[b]pyrroles that combine conformational biasing and transition state charge mimicry, is described. The key steps in this synthesis involve synthesis of (2-azido-1,3-dihydroxy-cyclopentyl)-acetic acid ethyl ester in four steps from cyclopentenone, followed by an efficient reductive cyclization of the azide to the bicyclic lactam. The lactam was subsequently converted into the corresponding bicyclic pyrrolidine, and analogs having phenyl, hydroxyl, and phosphate substituents. 相似文献
6.
13C Fourier transform NMR spectra of cis and trans 5-t-butyl-2-cyclohexenols, 2-cyclohexenol and their acetates have been examined indicating that the pseudo-axial orientation of the hydroxyl and the acetoxyl group at the allylic position is favoured in 2-cyclohexenol and its acetate. 相似文献
7.
Emine Salamci 《Tetrahedron》2010,66(23):4010-2897
A concise and efficient synthesis of cyclooctane-1,2,3,4-tetraoles, new polyhydroxylated eight-membered carbocycles, is described starting from cis,cis-1,3-cyclooctadiene. Cyclooctene endoperoxide obtained by photooxygenation of cis,cis-1,3-cyclooctadiene was the key compound in the synthesis. Reduction of the endoperoxide with zinc or thiourea followed by acetylation of the hydroxyl group and OsO4/NMO oxidation of the double bond gave (1R(S),2S(R),3R(S),4S(R))-cyclooctane-1,2,3,4-tetraol. Interestingly, epoxidation of cyclooctene-1,4-diol with m-CPBA also afforded trans-epoxy-diol 17. (1R(S),2R(S),3R(S),4S(R))-cyclooctane-1,2,3,4-tetraol was easily obtained by hydrolysis of epoxy-diol 17. 相似文献
8.
He Seung Lee Seung-Sock Choi Kyung-Youl Baek Soon Man Hong Eung Chan Lee Jong-Chan Lee Seung Sang Hwang 《European Polymer Journal》2012,48(6):1073-1081
The stereo cyclic siloxane compounds having tetra hydroxyl and tetra methyl group were synthesized by hydrolysis of tetrahydrido tetramethyl cyclosiloxane consisting of four stereoisomers. Among the stereo cyclic isomers, cis-trans-cis tetrahydroxyl tetramethyl cyclosiloxane (2) was separated by recrystallization and was used as a monomer species for preparation of ladder-like polymethylsilsesquioxane (PMSQ). The isolated isomer was directly polymerized in THF with potassium carbonate (K2CO3) by systematic ring condensation. The hydrolyzed stereoisomers were characterized by 1H and 29Si NMR, and HPLC. The structure of the synthesized PMSQs were characterized by size exclusion chromatography (SEC), MALDI-TOF mass, 29Si NMR, and small angle X-ray scattering (SAXS). 相似文献
9.
Marisa Mena 《Tetrahedron》2006,62(39):9166-9173
Birch reduction of homotyramines with a syn-β-amino alcohol unit followed by acid treatment of formed dihydroanisole derivatives gives polysubstituted enantiopure cis-decahydroquinolines. The stereoselectivity of the process differs if the hydroxyl group is free or protected. The procedure allows the synthesis of 7-oxodecahydroquinolines embodying four stereogenic centres with the same relative configuration as that of lepadins F and G. 相似文献
10.
《Tetrahedron: Asymmetry》2005,16(5):935-939
We have achieved a short, efficient stereoselective synthesis of 7-membered oxepane derivatives with potential against asthma. Highlights of our synthetic strategy are regioselective oxidation of a hydroxyl group and efficient ring closure of an open chain aldehyde to a 2-benzenesulfonyl oxepane derivative with PhSO2H. Surprisingly the cis-isomer showed better activity than the trans-isomer. 相似文献
11.
1H NMR conformational studies of cis-3(4) epoxy bicyclo (4.1.0) heptanes endo and exo, and of related alcohols (3-norcaranols) has been carried out using Eu(dpm)3 as shift reagent. Comparatively the conformational analysis of cis and trans-1(2), -4(5) diepoxy cyclohexanes has been performed. The experimental data agree with a predominant planar conformation of the two -3(4) epoxy bicyclo (4.1.0) heptanes and of the cis diépoxy cyclohexane, but do not distinguish between the planar conformation and the equilibrium of the two equivalent boat conformations of the trans diepoxyde. For the two alcohols, they adopt the same semi chair form in which the hydroxyl group is axial for the exo isomer and equatorial for the endo. 相似文献
12.
Two new kinds of docetaxel compound, with a mercapto group instead of the hydroxyl on the C13 side chain (both syn and anti), via the 7,10-di-(2,2,2-trichloroethyloxycarbonyl)-10-deacetylbaccatin III route, were synthesized. The uses of trans and cis oxazoline compounds, and their stereoselective ring-opening reactions with thiolacetic acid, were proved to be key steps. 相似文献
13.
Kenta IinoShogo Iwamoto Yuta KasaharaKana Matsuda Takashi TonozukaAtsushi Nishikawa Yukishige Ito Ichiro Matsuo 《Tetrahedron letters》2012,53(33):4452-4456
The fluorescence-labeled hexasaccharide (Glcα1-2Glcα1-3Glcα1-3Manα1-2Manα1-2Manα) was synthesized as a substrate for the processing enzyme α-glucosidase I. To construct the 1,2-cis glucosidic linkages, we employed an α stereoselective coupling using the mannosyl donor by assisted neighboring-group participation, followed by conversion of the stereochemistry of the C-2 hydroxyl group in the mannose residue using sequential oxidation of C-2 hydroxyl group to a 2-keto group and stereoselective reduction of the hydroxyl group to the gluco-configuration to provide the corresponding α-glucoside derivative. Using this strategy, the three consecutive α-glucosidic linkages were easily obtained in a stereoselective manner. Finally, the Dansyl labeled hexasaccharide derivative was used to measure the activity of processing α-glucosidase I. 相似文献
14.
13C Fourier transform NMR of cis and trans 5 - t - butyl - 2 - methyl - 2 - cyclohexenol, 2 -methyl - 2 - cyclohexenol and their acetates has been examined indicating that the pseudo-axial orientation of the hydroxyl and the acetoxyl group at the allylic position is favoured in 2 - methyl - 2 -cyclohexenol and its acetate. 相似文献
15.
A series of nucleophiles was reacted with 1,1,2,4,4,5,7,7,8,8,9,9,9-tridecafluoro-5-trifluoromethyl-3,6-dioxanon-1-ene (1) as a representative of perfluoro(alkyl vinyl ethers). All reactions were completely regioselective with the nucleophilic attack at the terminal carbon atom. Reactions of hydroxy compounds, thiols and sec-amines afforded addition products, but butyllithium, tributylphosphane or complex hydrides caused displacement of vinylic fluorine: butyllithium afforded cis-derivative, while reactions with hydrides and the phosphane led to mixtures of cis- and trans-derivatives. Diethylamine and piperidine adducts displayed the property to substitute hydroxyl for fluorine in hexadecan-1-ol. Molecular properties of hexafluoropropene and perfluoro(methyl vinyl ether) were calculated by ab initio method at the MP2/6-311G(d,p) level of theory and their impact on relative reactivity was estimated. 相似文献
16.
Comfort M. Nkambule Nomfundo W. KweziHenok H. Kinfe Mbulelo G. NokwequDavid W. Gammon Stefan Oscarson Erik Karlsson 《Tetrahedron》2011,67(3):618-623
A cis-1,2-cyclohexanediol, 1,4,5,6-tetra-O-benzyl-myo-inositol, was selectively protected at the axial C2-hydroxyl via acid-mediated rearrangement of the corresponding 1,2-orthoacetate, or via the base-induced migration of a protecting group that had previously been easily installed with complete regioselectivity at the adjacent equatorial hydroxyl. Esters 4a-6a were synthesized in high yields (75-82%) while sulfonate 7a and silyl ether 8a were obtained in 85 and 31% yields, respectively. The migration of the esters induced by DBU results in equilibrium between regioisomers favouring the C2 protected isomer, but NaH induced migration of sulfonyl and silyl groups results in complete migration from equatorial to axial hydroxyl groups. 相似文献
17.
《Tetrahedron: Asymmetry》1998,9(21):3745-3749
A surprisingly high level of cis-stereoselectivity in the Payne epoxidation has been identified with the homoallylic alcohol, terpinen-4-ol. Very high efficiencies for hydrogen peroxide are realized under mild conditions. The necessity for peroxyimidic acid stabilization by solvent is replaced by coordination to the directing hydroxyl function, resulting in dramatically improved space yields at up to the one kilogram scale. 相似文献
18.
《Mendeleev Communications》2022,32(5):680-682
New effective antioxidants of cis-2,4,5-tris(hydroxyaryl)imidazoline type were assembled from aromatic aldehydes and ammonia. Their antioxidant activity was measured against hydroxyl radical and superoxide radical anion in physiological media, and oxidation potentials were measured by cyclic voltammetry. The lead compound bearing 3,4,5-hydroxyphenyl moieties showed activity 3.5 times higher compared to Trolox. 相似文献
19.
The first syntheses of four stereoisomeric diaminocyclooctane diols, as well as a chlorocyclooctane aminodiol, are reported. In the first part, photooxygenation of cis,cis-1,3-cyclooctadiene gave a bicyclic endoperoxide, which was reduced with zinc followed by mesylation of the hydroxyl groups. Treatment with sodium azide afforded 1,4- and 1,2-cyclooctene diazides. Oxidation of the double bonds in the isomeric diazides with OsO4, followed by hydrogenation of the azide groups, led to 3,8-diaminocyclooctane-1,2-diol and 3,4-diaminocyclooctane-1,2-diols. In the second part, cis-3,8-diazidocyclooctene was converted into the corresponding epoxide. Stereospecific hydrolysis of the epoxide ring with HCl(g) in methanol, and hydrogenation of the azide groups gave 3,8-diamino-2-chloro-cyclooctan-1-ol. Bromination of the double bond in cyclooctene diacetate, followed by acetate deprotection, azidolysis of the bromides, and hydrogenation of the azide groups resulted in the formation of 2,3-diaminocyclooctane-1,4-diol. 相似文献
20.
All-cis cyclitols derived from cyclopentane have been prepared in two ways: (i) by LiAlH4 reduction of all-cis epoxypolyos; (ii) by dimethyl sulfoxide treatment, in the presence of sodium hydrogencarbonate, of brominated derivatives containing a neighbouring benzoyloxy group; under these conditions, the halogen is replaced by a cis-oriented hydroxyl group. Thus all-cis cyclopentane-tetrol and -pentol have been prepared; their configuration has been confirmed by NMR. spectroscopy. 相似文献