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1.
A number of ,β-unsaturated sulfinyl chlorides 1 has been separately prepared and treated with (−)-cholesterol under various conditions some of which incorporated chiral amines quinine or quinidine. Some (RS) vinylic sulfinates could be isolated in enantiopure form following one or two recrystallizations of the resulting diastereomeric mixtures of (−)-cholesteryl 1-alkenesulfinates 2. Access to diastereomerically enriched (SS) vinylic sulfinates (66–75% de) was achieved in three instances. Absolute stereochemical assignments were made with the assistance of the chiral solvating agent (R)-2,2,2-trifluoro-1-(9-anthryl)ethanol. 相似文献
2.
An intramolecular dehydrogenative homo-and hetero-coupling of phenols has been successfully developed for quick preparation of enantiopure axial diphenols under mild Cu(Ⅱ)-mediated conditions,using((4 S,5 S)-2,2-dimethyl-1,3-dioxolane-4,5-diyl)dimethanol as the chiral auxiliary.The commercially available(R)-α-met hylbenzy la mine was identified as the best amine ligand for Cu(Ⅱ) in the reactions.A variety of homo/hetero bis-dihydroxylbenzoate substrates were examined,affording the corresponding axially chiral diphenols with satis factory to excellent diastereomeric ratios,and a representative scalable preparation was also attempted.A formal synthesis of natural product(+)-deoxyschizandrin has been achieved in this work using one axially chiral diphenol as the synthetic intermediate. 相似文献
3.
Simonetta Orlandi Marinella Caporale Maurizio Benaglia Rita Annunziata 《Tetrahedron: Asymmetry》2003,14(24):3827-3830
Starting from the commercially available enantiopure (1S,2S)-2-amino-1-phenyl-1,3-propanediol novel enantiomerically pure benzimidazoles were prepared; N-alkylation gave chiral benzimidazolium salts, which were tested in asymmetric benzoin condensations. The synthesis of conceptually new, enantiomerically pure, C2 symmetric bis-thiazolium and bis-benzimidazolium salts was also developed. These new chiral heterocycles were employed as catalysts in the asymmetric dimerisation of benzaldehyde to give benzoin with moderate enantioselectivity. 相似文献
4.
[structure: see text] The chiral recognition ability of enantiopure O-methyl, O-ethyl, O-propyl, and O-phenyl phenylphosphonothioic acids (1a-d) for various kinds of racemic amines during salt crystallization and the chiral recognition mechanism were thoroughly investigated. The chiral recognition abilities of enantiopure 1a-d for a wide variety of racemic amines varied in a range of 6 to >99% enantiomeric selectivity. Deposited less-soluble diastereomeric salts were classified into two categories, prism- and needle-type crystals; the prism-type crystals were composed of a globular molecular cluster, while there existed a 2(1) column in the needle-type crystals. In contrast to a general observation of a similar 2(1) column in the less-soluble diastereomeric salt crystals of chiral primary amines with chiral carboxylic acids, the globular molecular cluster is a very unique hydrogen-bonding motif that has never been constructed in diastereomeric salt crystals. Excellent chiral recognition was always achieved when the less-soluble diastereomeric salts were prism-type crystals. Significant correlations were found between the degree of the chiral recognition with 1a-d, the crystal shape of the less-soluble diastereomeric salts, and the hydrogen-bonding motif (molecular cluster/2(1) column). The chiral recognition mechanisms via the molecular cluster and the 2(1) column formations are discussed in detail on the basis of X-ray crystallographic analyses. 相似文献
5.
Reaction of CpCoI2(P(OMe)3) 8 with the chiral aminophosphine (S)-(−)-diphenyl-phenylethylaminophosphine affords the diastereomeric phosphonate complexes (R,S)Co,SC-CpCoI(P(0)(OMe)2)(PPh2NHCH(Me)Ph) (10a,10b) via Arbuzov dealkylation. 10a,10b are separable and configurationally stable in solution for extended periods. The structure and absolute configuration of the lower Rf diastereomer (−)-436-10b were determined via single-crystal X-ray diffraction. It crystallizes as a toluene solvate in space group P21 with a 13.194(6), b 9.062(4), c 17.023(5) Å, β 108.78(3)°, Z = 2, and was refined to R = 0.067 for 6318 reflections. Spectroscopic and structural evidence demonstrate a strong 1,6 intramolecular NH O=P hydrogen bond between the aminophosphine NH and the basic phosphoryl oxygen, which establishes a quasi-boat conformation. Proton nuclear Overhauser difference spectra show that the conformation in solution is the same as that observed in the solid state. 相似文献
6.
《Tetrahedron: Asymmetry》2006,17(6):967-974
Enantiopure O-phenyl ethylphosphonothioic acid 1 was easily obtained by the enantioseparation of racemic 1, which was prepared from commercially available phosphorothioic trichloride in four steps. Enantiopure 1 was found to show an excellent chiral recognition ability for various 1-arylethylamine derivatives during the diastereomeric salt formation. In particular, enantiopure 1 was able to recognize the chirality of o- and m-substituted 1-arylethylamine derivatives, of which the chirality is generally difficult to establish by conventional resolving agents. X-ray crystallographic analyses of the less-soluble diastereomeric salts revealed that the conformation of the phenoxy group in enantiopure 1 could change in the diastereomeric salt crystals and that the excellent chiral recognition ability of enantiopure 1 resulted from the effective CH/π interaction of the phenoxy phenyl group. 相似文献
7.
Masato Matsugi Kinji Hashimoto Masatoshi Inai Norio Fukuda Takuya Furuta Jun-ichi Minamikawa Sei Otsuka 《Tetrahedron: Asymmetry》1995,6(12):2991-3000
A practical synthetic method for a xanthine dehydrogenase inhibitor, (S)-(−)-BOF-4272, was established utilizing an asymmetric oxidation of diaryl sulfide BOF-4269. The oxidation of the sulfide with 1-chlorobenzotriazole carried out in the presence of 4-cyanopyridine and chiral 2-phenylcyclohexanol gave a high enantiomeric excess (73%ee). The sulfoxides in each enantiomerically pure form could be obtained by treating with alkaline hydrolysis or thermolysis of one the diastereomeric intermediate sulfonium salts (>99%de). Thus the transformation into the sulfoxides occur with virtually perfect inversion (alkaline hydrolysis) or retention (thermolysis). It is therefore possible to obtain the target sulfoxide, (S)-(−)-BOF-4272, from both the two diastereomeric sulfonium intermediates. 相似文献
8.
《Liquid crystals》2000,27(10):1389-1392
Two diastereomeric carboxylic acids, 2(S)-[2(R)-methylhexyloxy]propionic acid and 2(S)[2(S)-methylhexyloxy]propionic acid, were prepared from ethyl (S)-lactate and (R)-1-iodo2-methylhexane or (S)-1-iodo-2-methylhexane in the presence of Ag2O. From these acids two liquid crystals, 2 and 3 , whose configurations are (S , R ) and (S, S) were synthesized and their liquid crystal properties investigated. Although both LCs have the same phase sequence Cr-SmC*-N*-I as well as a wide SmC* phase range, the influence of the relative stereochemistry on their physical properties is clear. The liquid crystal with (S, S)-configuration possesses better properties: lower SmC* phase transition temperature, wider SmC* phase range and higher Ps value. The Ps value difference between the ferroelectric LCs 2 and 3 (97 and 131nCcm-2, respectively, at Tc - T = 10°C) is unexpectedly large. The consideration, alone, of a zigzag conformation at the chiral molecular part of 2 and 3 is insufficient to explain such a difference. 相似文献
9.
Hassan Pajouhesh Mahmonir Hosseini-Meresht Seyed Hossein Pajouhesh Ken Curry 《Tetrahedron: Asymmetry》2000,11(24):4955-4958
The preparation of both enantiomers of 2-amino-3-(3-hydroxy-5-tert-butylisoxazol-4-yl) propanoic acid (ATPA), 1, an analogue of the neuroexcitant 2-amino-3-(3-hydroxy-5-methyl-4-yl) propanoic acid (AMPA) is described. The enantiomerically pure glycine derivative tert-butoxycarbonyl-2-(tert-butyl)-3-methyl-4-oxo-1-imidazolidinecarboxylate (BOC-BMI) was coupled with 4-bromomethyl-2-methoxymethyl-5-tert-butylisoxazolin-3-one 6 to give the intermediates (2R,5R)-8 and (2S,5S)-8. These alkylated products were hydrolyzed under mild conditions to give enantiopure (R)-1 and (S)-1 with e.e.'s in excess of 99% in 33% overall yield. 相似文献
10.
The resolution of racemic α-hydroxy-H-phosphinic acid with enantiopure 1-phenylethylamines via diastereomeric salt formation was investigated. X-Ray crystallographic analysis of the salt revealed that (R)-1-phenylethylamine to be efficient resolving agent for obtaining a single enantiomer of [α-hydroxy-(o-chlorophenyl)methyl]phosphinic acid. Resolving racemic α-hydroxy-H-phosphinic acid with (S)-2-phenylethylamine also gave access to (S)-α-hydroxyalkylphosphinic acid in good yield. 相似文献
11.
Yilun Yan Xinle Li Gui Chen Kai Zhang Xihao Tang Shuyuan Zhang Shengrun Zheng Jun Fan Weiguang Zhang Songliang Cai 《中国化学快报》2021,32(1):107-112
The designed synthesis of chiral covalent organic frameworks(COFs) featuring intriguing properties is fairly scant and remains a daunting synthetic challenge.Here we develop a de novo synthesis of an enantiomeric pair of 2 D hydroxyl-functionalized hydrazone-linked chiral COFs,(S)-and(R)-HthBta-OH COFs,using enantiopure 2,5-bis(2-hydroxypropoxy)terephthalohydrazide(Hth) as monomers.The fo rmation process of hydroxyl-functionalized chiral COFs was monitored using rigorous time-dependent PXRD,vibrational circular dichroism(VCD),and electronic circular dichroism(ECD) studies.Remarkably,VCD spectra indicated a unique chiral signal inversion from the positive Cotton effect of(S)-Hth monomer to the negative Cotton effect of(S)-HthBta-OH COF,which has never been reported in chiral COFs.Moreover,two unprecedented carboxyl-functionalized chiral COFs,(S)-and(R)-HthBta-COOH,were constructed by a post-synthetic modification of the corresponding hydroxyl chiral COFs with succinic anhydride.Notably,carboxyl-functionalized COFs retained homochirality and crystallinity without linker racemization and structural collapse after the chemical modification due to the chemically robust nature of pristine hydrazone-linked chiral COFs. 相似文献
12.
Tamio Hayashi Akihiro Yamamoto Masahiro Hojo Kohei Kishi Yoshihiko Ito
Eriko Nishioka
Hitoshi Miura Kazunori Yanagi 《Journal of organometallic chemistry》1989,370(1-3):129-139A new chiral ferrocenylphosphine ligand, 2,2′-bis[1-N,N-dimethylamino)ethyl]-1,1′-bis(diphenylphosphino)ferrocene (2), which has C2 symmetry and a functional group on the side chain, was prepared by ortho-lithiation and phosphination of 1,1′-bis[1-N,N-dimethylamino)ethyl]ferrocene followed by optical resolution; recrystallization of the diammonium salt with tartaric acid. An X-ray diffraction study of PdCl2[(+)-2] showed that the complex has square-planar geometry with two cis chlorine and two phosphorus atoms and ligand (+)-2 has an (S) configuration on the 1-dimethylaminoethyl side chain and (R) ferrocene planar chirality. 相似文献
13.
Miho Kusakari Yurie OhtaHideaki Nakagawa Hiroshi KatagiriTatsuro Kijima Satoshi MurakamiShigeru Matsuba Bunpei Hatano 《Tetrahedron letters》2014
An enantioresolution of 2-methoxy-2-(1-naphtyl)propionic acid (MαNP acid) using the diastereomeric salt with chiral (R)-phenylethylamine was achieved to give enantiopure (R)-MαNP acid in 29% yield with >99% ee based on rac-MαNP acid. X-ray crystallographic analysis of diastereomeric salt revealed that (R)-MαNP acid was tightly arranged by four independent hydrogen bonds and one CH–π interaction with (R)-phenylethylamine. 相似文献
14.
Chiral C2-symmetric 2,3-disubstituted aziridines and 2,6-disubstituted piperidines having a β-amino alcohol moiety have been successfully synthesized and their catalytic chiral induction properties have been examined in the asymmetric addition reactions of diethylzinc with arylaldehydes in hexane. When N-(2,2-diphenyl-2-hydroxyethyl)-(S,S)-2,3-bis(methoxymethyl)aziridine 11 was used as a catalytic chiral ligand, sec-alcohols having (S)-configuration formed in high yields of 86–92% but low enantiomeric excesses (ee's) of 11–13%. However, when N-(2,2-diphenyl-2-hydroxyethyl)-(R,R)-2,6-disubstituted piperidine derivatives 16 and 20 were used as the chiral ligands under the same reaction conditions, the ee's of the corresponding sec-alcohols were 20–30 and 5–6%, respectively, along with the inversion of absolute configuration. A plausible mechanism for this inversion is proposed. 相似文献
15.
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
16.
Vinyl substituted (1R,2S)-amino alcohols 5 were obtained by addition of vinyl magnesium bromide to the corresponding cyanohydrin O-trimethylsilyl ethers (R)-2. The O- and N-protected vinyl amino alcohols 6 were ozonized at −78°C in methanol yielding (1R,2S)-2-amino-1,3-diols7 in high enantiomeric and diastereomeric excesses. For purification, compounds 7 in some cases were acetylated to give the derivatives (1R,2S)-8. Racemic 6a was converted by oxidative ozonolysis at −78°C in methanolic NaOH solution to the corresponding methyl N-acetyl-β-hydroxy propanoate 9a. The configuration of (1R,2S)-8a was confirmed by x-ray crystallographic analysis. 相似文献
17.
Yutaka Aoyagi Naoki Agata Noriko Shibata Mai Horiguchi Robert M. Williams 《Tetrahedron letters》2000,41(52):4221-10162
The lipase TL®-mediated kinetic resolution of (±)-benzoin (1) proceeded to give the corresponding optically pure benzoin (R)-1. On the other hand, (S)-benzoin-O-acetate (5) could be hydrolyzed without epimerization to give (S)-benzoin (S)-1, under alkaline conditions. Further, (R)-1 was converted to (1R,2S)-2-amino-1,2-diphenylethanol (99:1 er) according to the procedure reported previously. 相似文献
18.
The use of a mono-pivalate mono-acrylate bis-ester of (+)-1S,5S,6S-spiro[4.4]nonane-1,6-diol in an asymmetric Diels-Alder reaction with cyclopentadiene (2 equiv. BCl3, −85°C, CH2Cl2) provided the expected endo bicyclo adduct in >97% de. Iodolactonization of the bicyclo adduct provided the (+)-lactone (5) with a 1S,4S,6S,8R,9S configuration (97% ee). The de's obtained from using various types and amounts of Lewis acids, and both chiral and racemic bis-esters in the Diels-Alder reaction with cyclopentadiene are also reported. 相似文献
19.
Moderate facial selectivities are observed in additions of alkyl radicals to the chiral (c,d) olefin (2S)-2-tert-butyl-5-ethoxycarbonylmethylene-1,3-dioxolane-4-one 1. The following hydrogen abstraction from tributylstannane proceeds with excellent asymmetric stereocontrol, leading to two of four possible diastereoisomers with high diastereomeric excesses. Additions of chiral radicals obtained from (2R,5R)-5-alkyl-5-bromo-1,3-dioxolane-4-ones to ethyl acrylate show high asymmetric 1,3-induction. 相似文献
20.
《Tetrahedron: Asymmetry》2006,17(10):1541-1543
The resolution of 1-cyclohexylethylamine 1 with enantiopure 2-phenylacetic acids via diastereomeric salt formation was investigated. (R)-2-Methoxy-2-phenylacetic acid 3 and the (S)-2-phenylpropionic acid 5 were found to be efficient resolving agents for obtaining the single enantiomer (S)-1 as the correspondingly less-soluble diastereomeric salt (resolution efficiency = 48% and 52%, respectively). 相似文献