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This paper reports efficient procedures for the preparation of optically active dibromide, diazide, diamine, and unsaturated diesters derived from a chiral bicyclic diol with C2 symmetry namely (11R,12R)-9,10-dihydro-9,10-ethaneanthracene-11,12-dimethanol 3. Esterification of 3 with saturated and unsaturated carboxylic acids and acids chlorides leads to the corresponding normal-, olefinic- and acetylenic diesters in average yields of 81%. Also more efficient techniques for the preparation of starting diol 3 in higher yields as well as for a very simple separation of DCU (N,N′-dicyclohexylurea) from reactions carried out following the DCC/DMAP method are described. 相似文献
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Recently, Nicolaou and Baran independently synthesized optically active 4-substituted 2-cyclohexenones via an efficient LiOH-mediated intramolecular aldol condensation. Thus far, application of their cyclization approach has been limited to ketoaldehydes where the R-group is branched. It is demonstrated that the LiOH-mediated cyclization, when applied to substrates containing unbranched R-groups, results in significant erosion of optical purity. A mechanistic justification is provided, and a set of neutral, organocatalyzed conditions is identified that enables cyclization with little loss in optical purity. 相似文献
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Daisuke NakanoRie Hirano Masahiko Yamaguchi Chizuko Kabuto 《Tetrahedron letters》2003,44(18):3683-3686
All six stereoisomers of dimethyl 5,5′-dihydroxy-1,1′,12,12′-tetramethyl-[6,6′]bi(benzo[c]phenanthrenyl)-8,8′-dicarboxylate (bihelicenol) were synthesized by the oxidative coupling of methyl 8-hydroxy-1,12-dimethylbenzo[c]phenanthrene-5-carboxylate (helicenol), and their structures were determined by X-ray analysis. 相似文献
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Conclusions S--(Distearoyl-L-phosphatidyl)--L-alanylglycerol and its R-isomer have been synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1098–1100, June, 1966. 相似文献
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Takashi Kitayama Sayo Ohta Yasushi Kawai Tomoyasu Nakayama Masataka Awata 《Tetrahedron: Asymmetry》2010,21(1):11-15
Tetrahydrozerumbone 2, which has a powerful balmy fragrance, has a stereogenic carbon at C2 and can be easily prepared from zerumbone 1, which is one of the most important materials that displays an NMRDOS character. Reduction of 2 gave two diastereomers 3 and 4; their optically active (>99% ee) alcohols were obtained by lipase-catalyzed stereoselective transesterification of each racemic alcohol. The enantioselectivity of tetrahydrozerumbol does not entirely depend on the hydroxyl position but on the 2-methyl position. Compounds (R)-2 and (S)-2 were obtained by Dess–Martin oxidation of the corresponding alcohols. Interestingly, (R)-2 showed a strong balmy fragrance while (S)-2 had hardly any fragrance. 相似文献
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Irina Guliaiko Vitaly Nesterov Sergei Sheiko Oleg I. Kolodiazhnyi Matthias Freytag Peter G. Jones Reinhard Schmutzler 《Heteroatom Chemistry》2008,19(2):133-139
The reduction of dimenthyl ketophosphonates with sodium borohydride involves asymmetric induction at the α‐carbon atom, resulting in a small excess of the (R)‐enantiomer of the α‐hydroxyphosphonate formed. A higher ee purity was achieved if the reduction of chiral dimenthyl ketophosphonates was carried out by the chiral complex of NaBH4‐L ‐proline, owing to the double asymmetric induction at the α‐carbon atom. The hydroxyphosphonates obtained were isolated in a diastereomerically pure state and were transformed to the optically active, free hydroxyalkylphosphonic acids. The (R)‐configuration of one of them was proved by X‐ray crystal structure analysis. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:133–139, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20391 相似文献
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V.M. Girijavallabhan A.K. Ganguly S.W. McCombie P. Pinto R. Rizvi 《Tetrahedron letters》1981,22(36):3485-3488
A general synthesis for optically active penems is described. Penems undergo a novel thermal isomerisation reaction. 相似文献
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John M. Ndungu 《Tetrahedron letters》2004,45(21):4139-4142
The cholecystokinin C-terminal octapeptide analogue H-Asp-Tyr-D-Phe-Gly-Trp-(N-Me)-Nle-Asp-Phe-NH2 (SNF 9007) is a potent and selective ligand for both the CCK-B and δ-opioid receptors. To constrain the peptide into the biologically active conformation(s), bicyclic dipeptide mimetics for Nle-Gly and homoPhe-Gly were designed and synthesized from β-substituted aspartic acids. Alkylation of L-aspartic acid using lithium bis(trimethylsilyl)amide (LHMDS) in the presence of hexamethylphosphoramide (HMPA) gave β-substituted aspartic acids, with the major product being the (2S,3R) isomer. Additional isomers of Nle-Gly bicyclic dipeptide mimetic were obtained via the Kazmaier-Claisen rearrangement reaction. The stereochemistries of the bicyclic dipeptide mimetics were assigned by X-ray and NMR. 相似文献
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John M. Ndungu 《Tetrahedron letters》2004,45(16):3245-3247
Alkylation of Nα-Boc protected aspartic acid with allyl bromide in the presence of lithium bis(trimethylsilyl)amide (LHMDS) and hexamethylphosphoramide (HMPA) afforded chiral β-allyl substituted aspartic acid in good yields. After deprotection of the Nα-Boc group and reprotection as a trifluoroacetamide, the terminal alkene was oxidized to an aldehyde. The aldehyde was then coupled with l-cysteine through a cascade three-bond formation process to afford aspartic acid-glycine bicyclic dipeptide mimetics. 相似文献
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Synthesis of an optically active unsaturated silicohydrocarbon containing an asymmetric silicon atom
S. L. Davydova Yu. A. Purinson B. D. Lavrukhin N. A. Platé 《Russian Chemical Bulletin》1965,14(2):373-375
Summary Starting with vinyltriethoxysilane, we were the first to obtain optically active dextrorotatory and levorotatory isomers of an unsaturated silicohydrocarbon, namely, of vinylphenyl--naphthylsilane.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 387–389, February, 1965 相似文献
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(+)-(R)-5-Methyl- and (+)-(R)-2,5-dimethyl-8-isopropylidene-5,6-dihydro-7H-quinoline, 7 and 11 , were synthesized by reaction of (R)-pulegon morpholino-enamine with acrolein or methyl vinyl ketone. The Michael adducts thus formed were reacted with hydroxylammonium hydrochloride in polar media. Compound 7 was also obtained by thermal rearrangement of the O-allyl ether of pulegone oxime. The selectivity of both synthetic methods were rather poor (30–49%). Isolation of 7 and 11 in the pure state was accomplished by preparative glc. 相似文献
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具有光学活性的炔丙醇是有机合成的重要中间体,其合成方法较多,通常使用 不对称还原、不对称1,2-加成、动力学拆分、2,3σ-重排、消除、还原裂解等 方法合成,其ee值和化学产率均达到了良好的水平,作者将对这类化合物的不对称 合成方法作一总结。 相似文献
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The synthesis of two selectively deuterium-labelled 4-(((S)-1-((S)-1-((S)-2-methylbutoxy)-1-oxopropan-2-yloxy)-1-oxopropan-2-yloxy)carbonyl)phenyl 4′-(heptyloxy)biphenyl-4-carboxylate derivatives is reported. A new preparation strategy was developed in order to optimise the yields as well as the optical purity, this property being of fundamental importance for the optical applications of this ferroelectric liquid crystal. 相似文献