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1.
Racemic 1,1′-methylene[(1RS,1′RS,3RS,3′RS,5RS,5′RS)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] ((±)-6) derived from 2,2′-methylenedifuran has been resolved kinetically with Candida cyclindracea lipase-catalysed transesterification giving 1,1′-methylenedi[(1R,1′R,3R,3′R,5R,5′R)-8-oxabicyclo[3.2.1]oct-6-en-3-ol] (−)-6 (30% yield, 98% ee) and 1,1′-methylenedi[(1S,1′S,3S,3′S,5S,5′S)-8-oxabicyclo[3.2.1]oct-6-en-3-yl] diacetate (+)-8, (40% yield, 98% ee). These compounds have been converted into 1,1′-methylenedi[(4S,4′S,6S,6′S)- and (4R,4′R,6R,6′R)-cyclohept-1-en-4,6-diyl] derivatives. 相似文献
2.
(1R,2R,3R,7aR)-1,2-Dihydroxy-3-hydroxymethylpyrrolizidine (+)-Hyacinthacine A2 1 has been synthesized by Wittig's methodology using [(2′S,3′R,4′R,5′R)-3′,4′-dibenzyloxy-N-tert-butyloxycarbonyl-5′-tert-butyldiphenylsilyloxymethylpyrrolidin-2′-yl]carbaldehyde 3, prepared from a partially protected DMDP 2, and the appropriated ylide, followed by cyclization by an internal reductive amination process of the resulting unsaturated aldehyde 4 and total deprotection. 相似文献
3.
The “naked sugar” (+)-(1R,2R,4R)-2-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl acetate ((+)-3) was converted in ten synthetic steps into the new C-nucleoside (1R)-1-C-(6′-amino-7′H-purin-8′-yl)-1,4-anhydro-3-azido-2,3-dideoxy- D-erythro-pentitol ((+)-2) in 19% overall yield. 相似文献
4.
Takahiro Hosokawa Takanori Kono Toru Shinohara Shun-Ichi Murahashi 《Journal of organometallic chemistry》1989,370(1-3):C13-C16
The oxidative cyclization of 2-(3-pentenyl)phenol catalyzed by [(η3-pinene)PdOAc]2 gives optically active (+)-2-vinylchroman (25% e.e.), while (−)-2-(1-hydroxyethyl)chroman (56% e.e.) is formed as a single diastereomer upon treatment with t-BuOOH in the presence of Ti(OiPr)4 and
-(+)-diethyl tartrate. 2-(2-Butenyl)phenol also undergoes the Ti-promoted asymmetric cyclization to give (2S,1′R)-(−)-2-(1-hydroxyethyl)-2,3-dihydrobenzofuran (29% e.e.). 相似文献
5.
Jacqueline Collin Fabien Carre Nicolas Giuseppone Isabel Santos 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):185-189
[(R)-1,1′bi-2,2′-Naphthoxy]LnI(THF)2 (Ln: Yb, Sm, La) 5 have been prepared by reaction of the bispotassium salt of (R)-binaphthol with lanthanide triiodides, and characterized. They are active catalysts for Diels–Alder reactions although with low asymmetric inductions. The lanthanum iodo bisbinaphthoxide gives a slightly higher enantiomeric excess than the two other complexes. 相似文献
6.
Tibor Novk Viktria Ujj Jzsef Schindler Mtys Czugler Mikls Kubinyi Zsuzsa A. Mayer Elemr Fogassy Gyrgy Keglevich 《Tetrahedron: Asymmetry》2007,18(24):2965-2972
The antipodes of 1-aryl-, 1-alkyl- and 1-alkoxy-3-methyl-3-phospholene 1-oxides 1a–h and 1-phenyl-3-methyl-3-phospholene 1-sulfide 1i were separated in good yields and high enantiomeric excesses (up to >99% ee) by resolution via formation of diastereomeric complexes with either (−)-(4R,5R)-4,5-bis(diphenylhydroxymethyl)-2,2-dimethyldioxolane 2 (TADDOL) or (−)-(2R,3R)-,,′,′-tetraphenyl-1,4-dioxaspiro[4.5]decan-2,3-dimethanol 3. The stereostructure of the supramolecular formations and the absolute configurations of the 3-phospholene oxides 1a, 1e and 1f were elucidated by single crystal X-ray crystallography. CD spectroscopy was also useful in determining the absolute configurations of some phospholene oxides 1b, 1c, 1g and 1h. 相似文献
7.
Gyrgy Keglevich Helga Szelke Andrea Kernyi Veronika Kudar Mikls Hanusz Klmn Simon Tímea Imre Krisztina Ludnyi 《Tetrahedron: Asymmetry》2005,16(24):4015-4021
The reaction of racemic chloro-dibenzo[c.e][1,2]oxaphosphorine with (S)-(−)--methyl-benzylamine and (1R,2S,5R)-(−)-menthol led to a mixture of optically active diastereomers of the corresponding phosphonous derivatives. The isomers were separated in a diastereomeric excess of 71–93% at the phosphonic oxide and/or at the phosphonous borane stage. The P(III) boranes are suitable precursors of the P-ligands. The absolute P-configuration in one of the menthyl phosphonates isolated was determined by single crystal X-ray analysis. 相似文献
8.
Edwin C. Constable Catherine E. Housecroft Valrie Jullien Markus Neuburger Ingo Poleschak Sbastien Reymann Sina Saxer Silvia Schaffner 《Polyhedron》2007,26(18):5519-5526
The chiral ligands, 4,4′-bis{(1S,2R,4S)-(−)-bornyloxy}-2,2′-bipyridine, (1S,2R,4S)-1, and 4,4′-bis{(1R,2S,4R)-(+)-bornyloxy}-2,2′-bipyridine, (1R,2S,4R)-1, have been prepared and characterized by spectroscopic techniques and, for (1S,2R,4S)-1, by single crystal X-ray diffraction. Despite the use of enantiomerically pure ligands, the formation of the complexes [Fe((1S,2R,4S)-1)3]2+, [Ru((1S,2R,4S)-1)3]2+, [Ru((1S,2R,4S)-1)(bpy)2]2+ and [Ru((1R,2S,4R)-1)(bpy)2]2+ proceeds without preference for either the Δ or Λ-diastereoisomers. 相似文献
9.
Werner Schroth Ekkehard Hintzsche Roland Spitzner Dieter Str hl Katrin Schmei Joachim Sieler 《Tetrahedron》1995,51(48):13261-13270
3-exo,3′-exo-(1R,1′R)-bicamphor (12) is obtained from 3-exo,3′-exo-(1R,1′R)-bithtiocamphor (3) by condensation with hydrazine hydrate followed by hydrolysis of the resulting dihydropyridazine 11. Deprotonation of 12 with NaH and subsequent treatment with potassium hexacyanoferrate (III) furnishes the 2,2′-dioxo-3,3′-bibornanylidene 13, whilst reduction of 12 with L1AlH4 affords the 3,3′-biisoborneol 16. Further related transformations to various 2,2′-difunctional 3,3′-bibornane derivatives are described, which are could be of interest as chiral ligands 相似文献
10.
On the basis of the chiral syntheses of (1′R)-I and (1′S)-I and of their 9-ribosides (1″R)-III and (1″S)-III from D- and L-alanines, the structures of the cytokinins 1′-methylzeatin and its 9-riboside have been established to be (1′R)-I and (1″R)-III. 相似文献
11.
C2-Symmetric (4S,4′S)-2,2′-bis(o-diphenylphosphinophenyl)-4,4′,5,5′-tetrahydro-4,4′-bi(1,3-oxazole) (1, Phos-Biox) has been designed and synthesized as a chiral ligand for metal-catalyzed reactions. The Phos-Biox 1 was found to be an efficient ligand for rhodium(I)-catalyzed asymmetric reduction of prochiral acetophenones with diphenylsilane to give optically active secondary alcohols of up to 97% ee. 相似文献
12.
Optically active, cage-functionalized crown ether (R)-3 which contains a 1,1′-bi-2-naphthol moiety has been prepared. Subsequently, the ability of (R)-3 to selectively recognize the enantiomers of guest ammonium salts, i.e., 4 and 5 in transport experiments was studied. Host (R)-3 displays significantly enhanced enantiomeric selectivity toward complex formation with 4 vis-à-vis complex formation with 5. The relative energetics of various relevant host–guest complexes have been investigated computationally. 相似文献
13.
Reaction of optically active ketone complexes (+)-(R)-[(η5-C5H5)Re(NO)-(PPh3)(η1-O=C(R)(CH3)]+ BF4− (R = CH2CH3, CH(CH3)2m C(CH3)3, C6H5) with K(s-C4H9)3BH gives alkoxide complexes (+)-(RS)-(η5-C5H5)Re(NO)(PPh3)-(OCH(R)CH3) (73–90%) in 80–98% de. The alkoxide ligand is then converted to Mosher esters (93–99%) of 79–98% de. 相似文献
14.
(+)-Carpamic acid [(2′R,5′S,6′S)-8-(5′-hydroxy-6′-methylpiperidin-2′-yl)octanoic acid, 1] was synthesized from (S)-alanine, employing intramolecular and reductive amination of acyclic amino ketone 8 as the key step to generate the piperidine ring. 相似文献
15.
Mariappan Periasamy Muthu Seenivasaperumal Vutukuri Dharma Rao 《Tetrahedron: Asymmetry》2004,15(24):3847-3852
Methods of synthesis of new chiral amino ether derivatives through the opening of aziridinium ions, prepared in situ using trans-(±)-2-(1-N,N-dialkylamino)cyclohexyl mesylate with (R)-(+)-1,1′-bi-2-naphthol, are described. The (R,R,R)-diastereomer was obtained as the major product and isolated as an enantiopure salt, and characterized by single crystal X-ray analysis. The C2-chiral (R,R,R,R,R)-diamino ether was obtained as the major product by opening of the aziridinium ion, prepared using trans-(±)-2-(1-pyrrolidino)cyclohexyl mesylate and (R)-(+)-1,1′-bi-2-naphthol in the presence of aq NaOH. This was also characterized by single crystal X-ray analysis. 相似文献
16.
Yi Yang Chenglu Zhang Guoren Yue Pingyan Bie Xinfu Pan 《Tetrahedron: Asymmetry》2002,13(24):2689-2692
Two erythro-isomers of 2,2′-dimethoxy-4-(3-hydroxy-1-propenyl)-4′-(1,2,3-trihydroxypropyl)diphenyl ether, (7′S, 8′S)-9 and (7′R, 8′R)-9, were synthesized in seven steps, in which an improved method for the synthesis of the key intermediate 3 was developed. The absolute configuration of the target molecules was also confirmed. 相似文献
17.
Nicolas Giuseppone Jacqueline Collin Angela Domingos Isabel Santos 《Journal of organometallic chemistry》1999,590(2):593-252
The synthesis and characterization of novel enantiopure binaphthoxy-diiodo lanthanides [(R)-2-(1-naphthol)-1′-naphthoxide)LnI2(THF)3] (Ln=Sm (4a), Yb (4b), La (4c)) are described. These complexes have been prepared by reacting the mono potassium salt of (R)-binaphthol with the corresponding lanthanide triiodides and were characterized by elemental analysis, IR and NMR spectroscopies. Recrystallization of 4c from THF–hexane led to monocrystals of [(R)-2-(1-naphthol)-1′-naphthoxide)]-diiodolanthane-tetrakistetrahydrofurane] (4c*). Complex 4c* crystallizes in the orthorhombic space group, P212121 with cell parameters a=13.086(1) Å, b=15.496(1) Å, c=18.854(1) Å, V=3823.2(6) Å3, and Z=4. 相似文献
18.
Johannes C. S. Malan Jacobus A. Steenkamp Desmond A. Young Daneel Ferreira 《Tetrahedron》1989,45(24):7859-7868
Acid-catalyzed condensation of (+)-mollisacacidin-[(2R, 3S, 4R)-2, 3-trans-3, 4-trans-flavan-3,3′,4,4′,7-pentaol] with an excess of (−)-robinetinidol[(2R,3S)-2,3-trans-flavan-3,3′,4′,5′,7-pentaol] afforded a novel series of bi-, tri-, and tetraflavanoid profisetinidins. They are accompanied by (−)-fisetinidol-(4,2′)-(−)-robinetinidol which results from the pyrogallol B-ring of (−)-robinetinidol serving as nucleophile competing with its resorcinol A-ring in coupling with a C-4 carbocationic intermediate. Similar condensation with (+)-epifisetinidol[(2S,3S)-2,3-cis-flavan-3,3′,4′,7-tetraol] led to the exclusive formation of [4,6]-interflavanyl bonds, these units being ‘linearly’ arranged in the tetraflavanoid analogue in contrast to the ‘branched’ nature of the (−)-robinetinidol homologue. 相似文献
19.
The Schiff base compound, N-N′-bis(4-methoxybenzylidene)ethylenediamine (C18H20N2O2) has been synthesized and its crystal structure has been investigated by X-ray analysis and PM3 method. The compound crystallizes in monoclinic space group P21/n with a=10.190(1), b=7.954(1), c=10.636(1) Å, β=111.68(1)°, V=801.1(1) Å3, Z=2 and Dcal=1.229 Mgm−3. The title structure was solved by direct methods and refined to R=0.056 for 2414 reflections [I>3.0σ(I)] by full-matrix anisotropic least-squares methods. The energy profile of the compound was calculated by PM3 method as a function of θ[N1′–C9′–C9–N1]. The most stable molecular structure of the title compound is the anti conformation, which is different in energy by 5.0 and 1.0 kcal mol−1 from the eclipsed conformation I and gauche conformations, (III and V), respectively. 相似文献
20.
Toshiyuki Furutani Masanori Hatsuda Ritsuo Imashiro Masahiko Seki 《Tetrahedron: Asymmetry》1999,10(24):1317-4768
Enantiopure 1,1′-binaphthyl-2,2′-dicarboxylic acids (R)-1 and (S)-1 have been synthesized through the lipase-catalyzed kinetic resolution of the racemic 2,2-bis(hydroxymethyl)-1,1′-binaphthyl (±)-2 and subsequent oxidation of the hydroxymethyl groups. 相似文献