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1.
《Tetrahedron: Asymmetry》2001,12(3):357-360
A new and efficient methodology for the enantiopure synthesis of (3R,2aR)-(−)-3-phenyl-hexahydro-oxazolo[3,2-a]pyridin-5-one 3 starting from (1′R)-(−)-1-(2′-hydroxy-1′-phenyl-ethyl)-(1H)-pyridin-2-one 1 is described. In addition, the enantiospecific synthesis of (S)-(+)-coniine hydrochloride 6 in good yield from 3 is reported. 相似文献
2.
Jacqueline Jiménez Mildred López Vladimir Carranza Angel Mendoza Jenaro Varela Estibaliz Sansinenea Aurelio Ortiz 《Tetrahedron letters》2017,58(3):235-239
An alternative methodology for the synthesis of chiral 3-(p-tolyl) butanoic acids is presented. This was accomplished through the diastereoselective hydrogenation reaction of different chiral N-3-(p-tolyl) but-2-enamides, using Pd/C in EtOH, to produce the corresponding chiral N-3-(p-tolyl) butanamides with high chemical yields and moderate diastereomeric ratios. Removal of the chiral auxiliary from N-3-(p-tolyl) butanamides gave the respective enantiomerically pure acids. 相似文献
3.
Manuel Velasco Ulises Hernández Joel L. Terán Dino Gnecco María L. Orea David M. Aparicio Víctor Gómez-Calvario Sylvain Bernès Jorge R. Juárez 《Tetrahedron letters》2019,60(12):820-824
The stereoconvergent synthesis of N-Boc-(2R,3S)-3-hydroxy-2-phenylpiperidine from (R)-1-(2-((tert-butyldimethylsilyl)oxy)-1-phenylethyl)piperidin-2-one is described. The key steps involved are α-hydroxylation of quiral lactam with O2, stereoconvergent reduction of (R)- or (S)-3-(benzyloxy)-piperidin-2-one with Red-Al® which afforded in both cases the trans-bicyclic oxazolidine in high stereoselectivity after chromatographic purification and a stereospecific Grignard addition to chiral bicyclic oxazolidine. 相似文献
4.
Y. S. Salim A. Sharon S. Vigneswari M. N. Mohamad Ibrahim A. A. Amirul 《Applied biochemistry and biotechnology》2012,167(2):314-326
This paper investigates the degradation of polyhydroxyalkanoates and its biofiber composites in both soil and lake environment. Time-dependent changes in the weight loss of films were monitored. The rate of degradation of poly(3-hydroxybutyrate) [P(3HB)], poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-23?mol% 4HB)] and poly(3-hydroxybutyrate-co-3-hydroxyvalerate-co-4-hydroxybutyrate) [P(3HB-co-9?mol% 3HV-co-19?mol% 4HB)] were investigated. The rate of degradation in the lake is higher compared to that in the soil. The highest rate of degradation in lake environment (15.6?% w/w week?1) was observed with P(3HB-co-3HV-co-4HB) terpolymer. Additionally, the rate of degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-38?mol% 3HV)] was compared to PHBV biofiber composites containing compatibilizers and empty fruit bunch (EFB). Here, composites with 30?% EFB displayed the highest rate of degradation both in the lake (25.6?% w/w week?1) and soil (15.6?% w/w week?1) environment. 相似文献
5.
Reaction of 1,5-diphenyl-3-(2-pyridyl)pentane-1,5-dione (5a) with 2.5 moles of benzylpentacarbonylmanganese in petroleum spirit under reflux gives a small amount of the symmetric di-aryl-manganated product [1,5-diphenyl-κC2-3-(2-pyridyl)pentane-1,5-dione-κO1κO5]bis-(tetracarbonylmanganese) (7a), but mostly [1,5-diphenyl-κC2-3-(2-pyridyl-κN)pentan-2-yl- κC2-1,5-dione-κO1κO5]tetracarbonylmanganesetricarbonylmanganese (6a) which is manganated at only one aryl carbon [by Mn(CO)4] but also [by Mn(CO)3 with N and O coordination] at the methylene carbon adjacent to the Mn(CO)4-coordinated ketone carbonyl. The latter is a rare example of direct cyclomanganation at a saturated carbon and the only known case adjacent to a carbonyl group; the X-ray crystal structure of 6a is reported. With 3 moles of benzylpentacarbonylmanganese the yield of 6a remains unchanged but some trimanganation product [1,5-diphenyl-κC2′κC2?-3-(2-pyridyl-κN)pentan-2-yl-κC2-1,5-dione-κO1κO5]tris-(tetracarbonylmanganese) (8a) is formed, presumably from 7a. Routes to products are proposed and activating factors considered. 1,5-Di-(2-thienyl)-3-(2-pyridyl)pentane-1,5-dione (5b) and its 3-thienyl isomer (5c) similarly give 6a analogues [1,5-di-(2-thienyl-κC3)-3-(2-pyridyl-κN)pentan-2-yl-κC2-1,5-dione-κO1κO5]tetracarbonylmanganesetricarbonylmanganese (6b) and [1,5-di-(3-thienyl-κC2)-3-(2-pyridyl-κN)pentan-2-yl-κC2-1,5-dione-κO1κO5]tetracarbonylmanganesetricarbonylmanganese (6c).Also reported are the mono-cyclomanganation product [1-(2,6-dimethoxyphenyl)-3-(2-pyridyl-κN)prop-2-en-2-yl-κC2-1-one]tetracarbonylmanganese (16) and dicyclomanganation product [1-(2,5-dimethyl-3-thienyl-κC4)-3-(2-pyridyl-κN)prop-2-en-2-yl- κC2-1-one-κO ]bis-(tetracarbonylmanganese) (17) from reaction of the respective (E)-1-aryl-3-(2-pyridyl)prop-2-en-1-ones (3-(2-pyridyl)chalcones), the first reported examples of enone metallation at the α-carbon via N-coordination by a β-2-pyridyl group. 相似文献
6.
Shin-ichi Takekuma Kazutaka Mizutani Masaru Nakamura Toshie Minematsu Hideko Takekuma 《Tetrahedron》2007,63(18):3882-3893
Reaction of azulene (1) with all-trans-retinal in diethyl ether in the presence of hexafluorophosphoric acid at −10 °C for 1 h in a dark room gives the corresponding monocarbenium-ion compound, (2E,4E,6E,8E)-1-azulenyl-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ylium hexafluorophosphate (3), in 74% isolated yield. The spectroscopic, chemical, and electrochemical properties of 3 compared with those of the previously-documented (2E,4E,6E,8E)-1-(3-guaiazulenyl)-3,7-dimethyl-9-(2,6,6-trimethyl-1-cyclohexen-1-yl)-2,4,6,8-nonatetraen-1-ylium hexafluorophosphate (4) are reported. Along with the above delocalized monocarbenium-ion compounds 3 and 4, stabilized by the expanded π-electron systems possessing an azulenyl (or 3-guaiazulenyl) group, an efficient preparation as well as the spectroscopic, chemical, and electrochemical properties of (2E)-1-azulenyl-3-phenyl-2-propen-1-ylium and (2E)-1-(3-guaiazulenyl)-3-phenyl-2-propen-1-ylium hexafluorophosphates (5 and 6) (90 and 96% isolated yields), having a similar partial structure [i.e., the (2E)-1-azulenyl-2-propen-1-ylium-ion or (2E)-1-(3-guaiazulenyl)-2-propen-1-ylium-ion part] to those of 3 and 4, is documented. Moreover, the crystal structure of 6, whose carbenium-ion framework is planar, is shown. 相似文献
7.
Sonogashira coupling of (E)-α-iodovinylstannanes 1 with (trimethylsilyl)acetylene gave (Z)-1-(trimethylsilyl)-3-(tributylstannyl)alk-3-en-1-ynes 2, which underwent a desilylation reaction to afford (Z)-3-(tributylstannyl)alk-3-en-1-ynes 3 in high yields. (1E,3Z)-1-Halo-3-(tributylstannyl)-substituted 1,3-dienes 5 could be synthesized stereoselectively via hydrozirconation of (Z)-3-(tributylstannyl)alk-3-en-1-ynes 3, followed by trapping with iodine or NBS. 相似文献
8.
《Tetrahedron: Asymmetry》2000,11(20):4171-4178
For the synthesis of the potentially antipsoriatic vitamin D derivative 3 (Ro 65-2299) an efficient and multiselective enzymatic step had been developed in which the easily accessible trans-1,3,5-triacetoxy-cyclohexane 5 was selectively monohydrolyzed in the presence of the cis-isomer 8 to give (1R,3R)-1,3-diacetoxy-5-hydroxy-cyclohexane 6 in high enantiomeric excess (>99%) and yield (84%). Furthermore, for the synthesis of the enantiomer of 3, a simple and efficient enzymatic procedure for the asymmetric acetylation of cis-1,5-dihydroxy-3-(tert-butyldimethylsilanoxy)-cyclohexane 10 in an anhydrous organic solvent providing (1R,3S,5S)-1-acetoxy-3-hydroxy-5-(tert-butyldimethylsilanoxy)-cyclohexane 11 in >99% ee and quantitative yield is described. 相似文献
9.
《Tetrahedron: Asymmetry》2006,17(19):2775-2780
Enantiopure (−)-(1S,3S)-2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropanecarboxamide 2 and (+)-(1R,3R)-2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropanecarboxylic acid 3 were easily obtained from a multigram scale biotransformation of racemic amide or nitrile in the presence of Rhodococcus erythropolis AJ270 whole cell catalyst under very mild conditions. Coupled with efficient and convenient chemical manipulations, comprising mainly of the Curtius rearrangement, oxidation, and reduction reactions, chiral C2-symmetric (1S,2S)-3,3-dimethylcyclopropane-1,2-diamine 6 and ((1R,3R)-3-(aminomethyl)-2,2-dimethylcyclopropyl)methanamine 8 and pseudo-C2-symmetric (1S,3S)-3-(aminomethyl)-2,2-dimethylcyclopropanamine 11 were prepared. These were also transformed into the corresponding chiral salen derivatives 12, 13, and 14, respectively, in almost quantitative yields. 相似文献
10.
The Pd(PPh3)4-catalyzed isomerization of (Z)-1,4-diacetoxy-2-butene, (Z)-1-(t-butyldimethylsilyloxy)-4-acetoxy-2-butene and (Z)-1-(t-butyldiphenylsilyloxy)-4-acetoxy-2-butene affords the corresponding (E)-isomers and 1,2-difunctionalized-3-butenes. In THF, the formation of the (E)-isomers is mainly due to reaction from an η1-allylpalladium intermediate while an η3-allylpalladium is the main key intermediate in DMF. The time to reach equilibrium between the products and their respective concentrations depend on the nature of the substituents and the solvent. 相似文献
11.
《Tetrahedron: Asymmetry》2006,17(11):1705-1714
A stereoselective synthesis of a versatile chiral synthon possessing two stereogenic centers, (2S,3S)-3-[2-(5-benzyloxypyridyl)]-2-methyl-1,3-propane diol 12 (>99% ee), was achieved by using a chemo-enzymatic method. The conversion of (2S,3S)-12 to the homochiral intermediate (2S,3S,4S)-2-benzyloxycarbonylamino-4-[2-(5-benzyloxypyridyl)]-4-tert-butyldimethylsilyloxy-3-methylbutanoic acid 2 corresponding to the N-terminal amino acid congener of nikkomycin Z 1 is described. 相似文献
12.
Jianjun Xu 《Journal of fluorine chemistry》2007,128(1):71-77
A straightforward method to prepare symmetrical (1Z, 3Z)- and (1E, 3E)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes is described. High E/Z ratio 1-bromo-1-fluoroalkenes, prepared by isomerization from the E/Z ≈ 1:1 isomeric mixtures, reacted with Bu3SnSnBu3 and Pd(PPh3)4 to afford (1Z, 3Z)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes in good yield. (Z)-1-Bromo-1-fluoroalkenes, which were prepared by kinetic reduction from 1-bromo-1-fluoroalkenes (E/Z ≈ 1:1), can undergo similar reaction with Bu3SnSnBu3 and Pd(PPh3)4/CuI to prepare (1E, 3E)-2,3-difluoro-1,4-disubstituted-buta-1,3-dienes. 相似文献
13.
Stereoselective synthesis of cruciferous indole phytoalexin (R)-(+)-1-methoxyspirobrassinin and its unnatural (S)-(−)-enantiomer was achieved by spirocyclization of 1-methoxybrassinin in the presence of (+)- and (−)-menthol and subsequent oxidation of the obtained menthyl ethers. Methanolysis of menthyl ethers in the presence of TFA afforded (2R,3R)-(−)-1-methoxyspirobrassinol methyl ether as well its unnatural (2S,3S)-, (2R,3S)-, and (2S,3R)-isomers. 相似文献
14.
(Ra)-(R)2-2,2′-Bis(1-hydroxy-1H-perfluorooctyl)biphenyl ((Ra)-(R)2-1c), which is an axially dissymmetric ligand with two chiral centers, works as a good chiral auxiliary for asymmetric aldol reaction. Thus, the reaction of monopropanoyl ester of 1c (2) with benzaldehyde in the presence of triethylamine and titanium(IV) chloride gave (2R),(3S)- and (2R),(3R)-3-hydroxy-2-methyl-3-phenylpropanoic acid esters (3a) in an approximate ratio of 4:1 in a total high yield. This result shows that stereoselectivity at 2-position is quite high, while that at 3-position is moderate. Both isomers were easily separated by column chromatography. Methanolysis of the separated isomers gave nearly quantitative recovery of 1c by extraction with a fluorous solvent without any loss of ee, while methyl (2R),(3S)- or (2R),(3R)-3-hydroxy-2-methyl-3-phenylpropanoates were obtained by CH2Cl2 extraction quantitatively in >99% ee. Aldol reaction of 2 with various aldehydes gave similar results. 相似文献
15.
K. V. Shcherbakov Ya. V. Burgart V. I. Saloutin 《Russian Journal of Organic Chemistry》2006,42(12):1838-1844
5,6,7,8-Tetrafluoro-4-hydroxy-2H-chromen-2-one reacts with methylamine to give methylammonium 5,6,7,8-tetrafluoro-2-oxo-2H-chromen-4-olate, regardless of the solvent. The reaction of 3-acetyl-5,6,7,8-tetrafluoro-4-hydroxy-2H-chromen-2-one with the same amine in ethanol or acetonitrile leads to the formation of methylammonium 3-acetyl-5,6,7,8-tetrafluoro-2-oxo-2H-chromen-4-olate, while in dimethyl sulfoxide 5,6,8-trifluoro-7-methylamino-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione is formed. The latter is also formed in the reaction of 5,6,7,8-tetrafluoro-4-hydroxy-3-(1-iminoethyl)-2H-chromen-2-one with methylamine in DMSO, whereas in ethanol and acetonitrile 5,6,7,8-tetrafluoro-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione is obtained. 5,6,7,8-Tetrafluoro-3-(1-methylaminoethylidene)-3,4-dihydro-2H-chromene-2,4-dione reacts with methylamine, yielding 7-mono-or 5,7-bis(methylamino)-substituted derivatives. 相似文献
16.
I. V. Mineeva 《Russian Journal of Organic Chemistry》2013,49(6):838-842
A simple and efficient asymmetric synthesis of (5S,7R)-7-hydroxydodecano-5-lactone, a component of the giant danaine butterfly Idea leuconoe pheromone, and formal syntheses of (+)-(3R,5R)-3-hydroxydecano-5-lactone, verbalactone, and Tolypothrix pentaether have been accomplished starting from methyl (3R,5R)-3,5-dihydroxydecanoate. The latter is obtained from methyl 3-[(tributylstannyl)methyl]but-3-enoate using Keck allylation in the key step of the construction of its carbon skeleton. 相似文献
17.
Florian Blasberg 《Journal of organometallic chemistry》2011,696(23):3593-3600
The synthesis, structural characterization, and coordination behavior of ditopic ortho-hydroquinone-based bis(pyrazol-1-yl)methane ligands (ortho-(OH)2C6H3-4-CHpz2, ortho-(OH)2C6H3-4-CH(3-Phpz)2, and ortho-(OH)2C6H3-4-CH(3-tBupz)2) with pyrazole, 3-phenylpyrazole, and 3-tert-butylpyrazole as donors are described. The reaction of a soluble PdCl2-source with ortho-(OH)2C6H3-4-CHpz2 in acetonitrile yielded the related square-planar N,N-coordinated Pd(II) dichloride complex, whereas treatment of ortho-(OH)2C6H3-4-CH(3-Phpz)2 or ortho-(OH)2C6H3-4-CH(3-tBupz)2 with PdCl2 in acetonitrile resulted in degradation of these ligands. The Pd(II) complexes trans-(3-PhpzH)2PdCl2 and trans-(3-tBupzH)2PdCl2 were isolated and fully characterized including X-ray diffraction analyses. 相似文献
18.
E. A. Dikusar V. I. Potkin S. K. Pyatkevich 《Russian Journal of General Chemistry》2014,84(9):1701-1705
Preparative method for the synthesis of lithium, sodium, cesium, and calcium salts of (E)-4-(5-arylisoxazol-3-yl)methyleneaminobutanoic, (E)-6-(5-arylisoxazol-3-yl)methyleneaminohexanoic, (E,S)-3-methyl-2-(5-arylisoxazol-3-yl)methyleneaminobutanoic, (E,S)-4-methyl-2-(5-arylisoxazol-3-yl)methyleneaminopentanoic and (E,2S,3S)-3-methyl-2-(5-arylisoxazol-3-yl)methyleneaminopentanoic acids was developed by reacting 5-phenyl(4-tolyl)isoxazole-3-carbaldehydes with amino acids like 4-aminobutyric and 6-aminocaproic acids, L-valine, L-leucine or L-isoleucine in the presence of lithium hydride, sodium methoxide, cesium carbonate or calcium hydride in boiling methanol. 相似文献
19.
The β-galactosidase from bovine testes (EC 3.2.1.23) promotes the transfer of a galactose unit to glucose or galactose-containing residues in manifold derivatives, establishing β1→3 linkages.The synthesis of several potentially biologically important oligosaccharides β-d-Galp-(1→3)-α-d-Glcp-(1→2)-β-d-Fruf2, β-d-Galp-(1→3)-β-d-Galp-(1→4)-α,β-d-Glcp4, β-d-Galp-(1→3)-α-d-Glcp-(1→4)-d-Glcp-ol/Manp-ol 6, β-d-Galp-(1→3)-α-d-Glcp-(1→6)-β-d-Fruf8, β-d-Galp-(1→3)-α-d-Glcp-(1→6)-[α-d-Glcp-(1↔2)]-β-d-Fruf10, α-d-Galp-(1→6)-[β-d-Galp-(1→3)]-α-d-Glcp-(1↔2)-β-d-Fruf12, β-d-Galp-(1→3)-α-d-Glcp-(1↔2)-β-d-Fruf-(1↔2)-β-d-Fruf14 has been reached in yields between 7 and 44% by implementation of this specific enzyme. In addition, we found that it is feasible to gain high yields without an enzyme-specific buffer and even making upscaled preparation on a gram scale. 相似文献
20.
《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