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1.
The 6 R configuration of (+)-cis-γ-irone [(+)- 4 ] was established by chemical correlation with (—)-camphor. (+)-cis-γ-irone [(+)- 4 ] was converted into (+)-cis-α-irone [(+)- 1 ], (?)-trans-α-irone [(minus;;)- 2 ], and (+)-β-irone [(+)- 3 ], which therefore also have the 6 R configuration. The 2 S configurations of (+)-cis-α-irone [(+)- 1 ] and (+)-trans-α-irone [(+)- 2 ] were determined by comparison of their circular dichroism with that of R-α-ionone [(+)- 5 ]. The 2 S configuration of (+)-cis-γ-irone [(+)- 4 ] was established by chemical correlation with (+)-cis-α-irone [(+)- 1 ]. 相似文献
2.
Hiroyuki Terashima Yui Mutoh Sen-ichi Aizawa Atsushi Taga Ikko Mikami Yutaka Itabashi Kaname Tsutsumiuchi Atsushi Yamamoto Shuji Kodama 《Journal of separation science》2023,46(6):2200827
Abscisic acid (2-cis,4-trans-abscisic acid) is a plant hormone that has an asymmetric carbon atom. We tried to separate the enantiomers of native abscisic acid by HPLC using a phenyl column and a chiral mobile phase containing γ-cyclodextrin. The optimum mobile phase conditions were found to be 0.8% (w/v) γ-cyclodextrin, 4% (v/v) acetonitrile, and 20 mM phosphate buffer (pH 6.0). It was found that (R)-abscisic acid was earlier detected than (S)-abscisic acid. Since γ-cyclodextrin is hardly retained on a phenyl column, it was suggested that (R)-abscisic acid formed a more stable complex with γ-cyclodextrin than the (S)-abscisic acid. Abscisic acid in an acacia honey sample was successfully enantioseparated with the proposed method and only (S)-abscisic acid was detected. A biologically inactive 2-trans,4-trans-abscisic acid, which was prepared by irradiation of abscisic acid with a light-emitting diode lamp at 365 nm, was partially enantioseparated by the proposed method. Since the irradiation of (S)-abscisic acid-induced cis-to-trans isomerization to produce one 2-trans,4-trans-abscisic acid enantiomer, it is reasonable that racemization did not proceed during the cis-to-trans isomerization. (S)-Abscisic acid and probably (S)-2-trans,4-trans-abscisic acid were detected in a honey sample, where the peak area of (S)-abscisic acid was 7 times larger than that of (S)-2-trans,4-trans-abscisic acid. 相似文献
3.
Elisabetta Brenna Claudio Fuganti Giovanni Fronza Luciana Malpezzi Annalisa Righetti Stefano Serra 《Helvetica chimica acta》1999,82(12):2246-2259
The preparation of (−)- and (+)-trans-α-irone ( 1a and 1b , resp.) and of (+)- and (−)-cis-α-irone ( 1c and 1d , resp.) from commercially available Irone alpha ® is reported. The relevant step in the synthetic sequence is the initial chromatographic separation of crystalline (±)-4,5-epoxy-4,5-dihydro-cis-α-irone ((±)- 5 ) from oily (±)-4,5-epoxy-4,5-dihydro-trans-α-irone ((±)- 4 ). The latter was subsequently converted, after NaBH4 reduction, into the crystalline 3,5-dinitrobenzoate ester (±)- 8 , thus allowing a complete separation of the two corresponding diastereoisomeric alcohol derivatives. Suitable enantiomerically pure precursors of the desired products 1a – d were obtained by kinetic resolution of the racemic allylic alcohols derived from (±)- 5 and (±)- 8 , mediated by lipase PS (Amano). The last steps consisted of MnO2 oxidation and removal of the epoxy moiety with Me3SiCl/NaI in MeCN. External panel olfactory evaluation showed that (−)-cis-α-irone ( 1d ) has the finest and most distinct `orris butter' character. 相似文献
4.
A 3:1 mixture of (+)-(2S, 6S)-trans-α-irone ((+)-1) and (?)-(2S, 6S)-trans-γ-irone (?)-2) has been synthesized with ca. 70% e. e. by the ene reaction of (?)-(S)-3 and but-3-yn-2-one. 相似文献
5.
The β-dienoate (+)-(5S)- 13a (86% ee; meaning of α and β as in α- and β-irone, resp.) was obtained from (?)-(5S)- 9a via acid-catalyzed dehydration of the diastereoisomer mixture of allylic tertiary alcohols (+)-(1S,5S)- 15 /(+)-(1R,5S)- 15 (Scheme 3). Prolonged treatment gave clean isomerization via a [1,5]-H shift to the α-isomer (?)-(R)- 16a with only slight racemization (76% ee; Scheme 4). In contrast, the SnCl4-catalyzed stereospecific cyclization of (+)-(Z)- 6 to (?)-trans- 8a (Scheme 2), followed by a diastereoselective epoxidation to (+)- 11 gave, via acid-catalyzed dehydration of the intermediate allylic secondary alcohol (?)- 12 , the same ester (+)- 13a (Scheme 3), but with poor optical purity (13% ee), due to an initial rapid [1,2]-H shift. The absolute configuration of (?)- 16a–c was confirmed by chemical correlation with (?)-trans- 19 (Scheme 4). 13C-NMR Assignments and absolute configurations of the intermediate esters, acids, aldehydes, and alcohols are presented. 相似文献
6.
Optically active prostaglandin intermediates, 4(R)-(+)- and 4(S)-(?)-hydroxycyclopent-2-en-1-one derivatives, were synthesized from 3(R),5(R)-diacetoxycyclopent-1-ene, 3(R)-acetoxy-5(R)-hydroxycyclopent-1-ene and 3(S),5(S)-dihydroxycyclopent-1-ene obtained by microbiological hydrolysis of 3,5-diacetoxycyclopent-1-ene. The absolute configurations of all these compounds were determined by the exciton chirality method and the induced CD method. The optical purities were determined by NMR measurements of the diastereomeric esters of a versatile optically pure acid, (+)-α-methoxy-α-trifluoromethylphenylacetic acid. 相似文献
7.
Natural (+)-dactyloxene-B (12) and -C (13) have been synthesized starting from (+)-trans-2, 5, 6-trimethyl-l-cyclohexene-l-carbaldehyde (1) which is shown to have the (5S, 6R)-configuration by chemical correlation with (+)-(2R, 3S, 6S)-2, 3, 6-trimethylcyclohexanone. The absolute configurations are therefore (2R, 5R, 9S, 10R) for (+)-dactyloxene-B and (2R, 5S, 9S, 10R) for (+)-dactyloxene-C. 相似文献
8.
100 Mc/s proton NMR. spectra of the two diastereoisomeric thujanes obtained by reduction natural thujone have been measured and are given a detailed analysis. The relative configurations of the two hydrocarbons are deduced. Together with the known R-configuration at C(1) the absolute configurations can be derived, (?)-cis-thujane having the (1R:4S:5R)- and (+)-trans-thujane the (1R:4R:5R)-configuration. It can be shown that the trans-isomer adopts a boat-like conformation of the bicyclohexane ring system whereas cis-thujane prefers a half-chair conformation with a flattened cyclopentane ring. 相似文献
9.
(+)-cis-Khellactone methyl ether ( 4 ) and (?)-trans-khellactone methyl ether ( 6 ) had earlier been assigned the absolute configurations 3′-S; 4′-S and 3′-S; 4′-R, respectively, on the basis of the FREUDENBERG , rule. Both compounds together with their defunctionalised derivatives (?)- 7 and (+)- 8 (=(+)-lomatin), obtained from a mixture of (+)-visnadin ( 1 ) and (+)-samidin ( 2 ), were investigated by the HOREAU method. A conformational analytical study showed that the optical yield should rise in the order 4 < 6 < 7 , 8. This order was found and the α-phenylbutyric acid liberated was always dextrorotatory. The centre 3′ of the khellactones and their derivatives must be R-chiral and not S. Treatment of (?)- 6 with pyridinium perbromide gave (?)-trans-3-bromokhellactone methyl ether ( 11 ) as orthorhombic crystals. The X-ray crystal structure determination was made using the anomalous scattering of the Mo-K α radiation by Br. The result, — centre 3′ R-chiral (fig. g) — showed that the HOREAU method was correct. 相似文献
10.
Herbert Cadosch Ulrich Vgeli Peter Rüedi Conrad Hans Eugster 《Helvetica chimica acta》1978,61(5):1511-1519
Structure and properties of 5-epi-flavoxanthin and 5-epi-chrysanthemaxanthin The absolute configurations of 5-epi-flavoxanthin ( 6 ) and 5-epi-chrysanthemaxanthin ( 7 ) prepared by acid catalysed rearrangement of semi-synthetic lutein epoxide 5 are shown to be (3S, 5S, 8R, 3′R, 6′R) and (3S, 5S, 8S, 3′R, 6′R), respectively. Contrary to published data [5] the relationship of the polyene chain and H3(18) on the dihydrofurane ring is cis for the pair of stereoisomers having a Δδ = δ (H? C(7)) ? δ (H? C(8)) = 0,22 ppm and 3J ≡ 0. These conclusions are in full accord with the chiroptical data. 相似文献
11.
Karl H. Schulte-Elte Herv Pamingle Arnold P. Uijttewaal Roger L. Snowden 《Helvetica chimica acta》1992,75(3):759-765
Acid-mediated cyclisation of trienone 8 , readily available from 2,3-dimethylbutanal ( 1 ; five steps: 47% yield), using fluorosulfonic acid (6.8 mol-equiv.) in 2-nitropropane at ?70°, afforded a 14:9:1 mixture (70% yield) of (±)-cis-α-irone ( 9 ), (±)-trans-α-irone ( 10 ), and (±)-β-irone ( 11 ). Other acidic conditions examined, using 95% aq. H2SO4 solution, 85% aq. H3PO4 solution, or SnCl4, gave inferior results. 相似文献
12.
Doz. Dr. H. Falk Prof. Dr. W. Fröstl Dr. K. Schlögl 《Monatshefte für Chemie / Chemical Monthly》1974,105(3):574-597
The absolute configuration of 2.2-spirobiindane-1.1-dione (2) was established as (+)-(2S) by correlation with a centrochiral key intermediate, namely by cyclization of (+)-(2R)-2-benzyl-2-methoxycarbonyl-1-indanone (9) withPPA.9 was obtained by oxidation of either methyl (+)-cis- ortrans-1-hydroxy-2-benzyl-indane-2-carboxylate (8 a, 8 b), whose absolute configurations were determined as (+)-(1S, 2R) and (1R, 2R), resp., byHoreau's method and whose optical purities by the NMR-method employing the esters with -methoxy--trifluoromethylphenyl-acetic acid. The active methyl esters8 were prepared starting from the corresponding racemic ethyl ketocarboxylate4, which on reduction afforded the stereoisomeric ethylcis- andtrans-1-hydroxyindane-2-benzyl-2-carboxylates (5 a, 5 b); their relative configurations were determined by NMR. The corresponding acids7 were resolvedvia the cinchonidine salts and obtained in high optical purity (100% fortrans, 80% forcis).Levorotatory2 was also prepared by resolution of the bis-aminoxyacetic acid derivative (via its bis-cinchonidine salt) and subsequent cleavage. [a]
D
max
of2 was determined as ±240° (benzene) by means of a chiral shift reagent. The racemization of2 withPPA under the conditions of the asymmetric synthesis was studied.
Mit 4 Abbildungen 相似文献
Mit 4 Abbildungen 相似文献
13.
M. Hudlický 《Journal of fluorine chemistry》1993,60(2-3):193-210
(+)-
-threo-4-Fluoroglutamic acid [(+)-(2S, 4S)-fluoroglutamic acid] has been synthesizedstarting with the natural (−)-4-trans-hydroxy-
-proline. Its acetylation at nitrogen followedby esterification with diazomethane afforded methyl 1-acetyl-trans-4-hydroxy-
-prolinatewhich was converted to methyl 1-acetyl-cis-4-fluoro-
-prolinate by means of diethylaminosulfurtrifluoride (DAST) or 2-chloro-1,1,2-trifluorotriethylamine. The mixture wasoxidized by ruthenium tetroxide to methyl 1-acetyl-cis-4-fluoro-
-pyrrolidin-5-one-2-carboxylate,whose acid hydrolysis yielded the title compound. A similar sequence of reactionsconverted cis-4-hydroxy-
-proline to (−)-
-erythro-4-fluoroglutamic acid [(−)(2R, 4S)-fluoroglutamic acid]. (−)-
-threo-4-Fluoroglutamic acid [(−)-(2R, 4R)-floroglutamicacid] was prepared analogously from trans-4-hydroxy-
-proline, obtained from its diastereomerby inversion of configuration at carbon 4 of the pyrrolidine ring using thediethyl azodicarboxylate-triphenylphosphine procedure. cis-4-Hydroxy-
-proline, necessaryfor the synthesis of (+)-
-erythro-4-fluoroglutamic acid [(+)-(2S, 4R)-fluoroglutamicacid], was prepared from trans-4-hydroxy-
-proline by benzyloxycarbonylation at thenitrogen, oxidation of the 1-benzyloxycarbonyl-trans-4-hydroxy-
-proline to 1-benzyloxy-carbonyl-4-oxo-
-proline, its reduction to 1-benzyloxycarbonyl-cis-4-hydroxy-
-proline anddeprotection of the latter at the nitrogen. (−)-cis-4-Fluoro-
-proline and (+)-trans-4-fluoro-
-proline were isolated after the hydrolysis of incompletely oxidized methyl 1-acetyl-cis-4-fluoro-
-prolinate and methyl 1-acetyl-trans-4-fluoro-
-prolinate, respectively. 相似文献
14.
Xiaoli Ma Erwei Li Fenghua Gao Liangdong Guo Yunfei Pei 《Natural product research》2016,30(3):276-280
A new sesquiterpene, (+)-S-1-methyl-abscisic-6-acid (1), together with five known compounds, (+)-S-abscisic acid (2), fusicoccin J (3), 3α-hydroxyfusicoccin J (4), (R)-5-hydroxymethylmellein (5) and 4-hydroxyphenethyl acetate (6) was isolated from the fermentation extract of Phomopsis amygdali, an entomogenous fungus isolated from Call midge. Their structures were determined mainly by analysis of MS and NMR spectroscopic data. Compounds 1–6 were tested for antimicrobial activity against three plant pathogenic fungi: Gibberella zeae, Verticillium albo-atrum, and Fusarium nivale, and two bacteria: Escherichia coli and Pseudomonas aeruginosa 2033E. As a result, compounds 1–4 displayed antibacterial activity against Gram-negative P. aeruginosa 2033E, and the minimum inhibition concentration (MIC value) of 1–4 is 30 μg/mL, 58 μg/mL, 26 μg/mL, and 26 μg/mL, respectively. 相似文献
15.
The chirality of all stereoisomeric muscarines has been determined. (–)-Muscarine chloride was converted to (+)-normuscarine, which in turn was oxidized to (+)-normuscarone. Epimerisation by acid catalysis of the latter gave a mixture of the C(2)-epimers, namely (+)-normuscarone and (–)-allo-normuscarone. From these were prepared by reduction with LiAlH4 optically active stereoisomeric noralcohols. The natural stereoisomeric muscarines so far isolated are: (+)-(2S, 3R, 5S)-muscarine, (–)-(2S, 3R, 5R)-allo-muscarine and (+)-(2S, 3S, 5S)-epi-muscarine. Identical chirality appears only at C(2). This fact has to be taken into consideration for further speculations about the biogenesis of muscarines. Optically active muscarone and normuscarone exhibit a strong Cotton effect at 300 nm, which is interpreted in terms of absolute configuration by analogy to optically active substituted cyclopentanones. Optically active allo-normuscarone exhibits a very weak Cotton effect only, presumably because of predominant pseudo-rotation. The relative stability of the stereoisomeric norketones has been determined. Normuscarone (cis-2,5) is by 0,39 kcal/mol more stable than allo-normuscarone (trans-2,5). 相似文献
16.
(+)-(1S, 3S, 6S, 8S)-and (?)-(1R, 3R, 6R, 8R)-4, 9-Twistadiene: Synthesis and Absolute Configuration A synthesis and the determination of the absolute configuration of (+)-(1S, 3S, 6S, 8S)- and (?)-(1R, 3R, 6R, 8R)-4, 9-twistadiene ((+)- and (?)- 4 , respectively) is described. Their chiroptical properties are compared with those of saturated twistane ((+)- and (?)- 5 ) as well as with those of the unsaturated and saturated 2, 7-dioxatwistane analogs (+)- and (?)- 9 , and (+)- and (?)- 10 , respectively, which also are compounds of known absolute configurations. 相似文献
17.
Enantiomerically pure methyl 5-bromo-5-deoxy-2,3-O- isopropylidene-β-D - (D - 5b ) and -β-l-ribofuranoside (l- 5b ) have been derived from (?)-(1R,2S,4R)-2-exo-cyano-7-oxabicylo[2.2.1]hept-5-en-endo,-yl (1′S)-camphanate ( 1 ) and (+)-(1S,2R,4S)-2-exo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-endo-yl(1′R)-camphanate ( 2 ), respectively, in 5 synthetic steps and 28% overall yield. Hydrolysis of D-5b and L - 5b afforded methyl 2,3-O isopropylidene-β-D -ribofuranoside (D -5a) and methyl 2,3-O-isopropylidene β-L-ribofuranoside (L-5a), respectively. The intermediate (+)-(1R,4R,5R,6R) 5-exo,6-exo-(isopropylidenedioxy)- 7 -oxabicyclo[2.2.1]heptan-2-one ((+)- 7 ) and its enantiomer(–)-7 were also obtained enantiomerically pure by resolution of (=)- 7 by the Johnson-Zeller method. In bothe approaches, the chiral auxiliaries ((–)- and (+)-camphanic acids, or (+)-(S)-N,S-dimethyl-S-phenylsulfoximide) were recovered at an early stage of the synthesis. 相似文献
18.
A concise enantiospecific synthesis of (S)-6,8-bis(methylsulfonyloxy)-octanoic acid (2), a ready precursor of (R)-(+)-α-lipoic acid (1), is reported. The key step of the synthesis is the coupling of the tosylate derived from (R)-malic acid with phenylpropyl magnesium bromide. A recently reported green procedure was used for the oxidative unmasking of the phenyl group, used as a latent carboxyl group. 相似文献
19.
The synthesis of the novel (3R,4R)-4-acetoxy-3-[(1S)-1-t- butyldimethylsilyloxymethyl-1-((1S)-1- phenylethylaminocarbonyl)]azetidin-2-one ( 1a ), a valuable key intermediate for penems and carbapenems bearing a 6-hydroxyacetamide side chain, and its diastereomer 1b , from dimethyl cis-2,3-oxirane dicarboxylate, is described. The allocation of absolute configurations to the diastereomers 1a and 1b ensued via single-crystal X-ray analysis of the isomer 1b. 相似文献
20.
Two new C12-ketones, (+)-(1S, 10R)-1,10-dimethylbicyclo[4.4.0]dec-6-en-3-one ( 5 ) and (+)-(6S, 10S)-6,10-dimethylbicyclo[4.4.0]dec-1-en-3-one ( 6 ), have been isolated from Reunion vetiver oil (Vetiveria zizanioides (L.) Nash). Structure and absolute configuration of 5 were established by a four-step synthesis from (+)-isonootkatone ((+)-α-vetivone) ( 1 ). The structure of 6 followed from its spectroscopic properties and was confirmed by direct comparison with an authentic racemic sample. The absolute configuration of 6 was established by chemical correlation with (+)-α-eudesmol ( 13 ). 相似文献