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1.
《Tetrahedron: Asymmetry》1999,10(22):4313-4319
3,7-Dimethyl-3(E)-octene-1,2,6,7-tetraol, a monoterpene recently isolated from Passiflora quadrangularis fruit pulp, has been established to be a 12:42:14:32 mixture of (2R,6R)-, (2R,6S)-, (2S,6R)- and (2S,6S)-stereoisomers, in that order, by HPLC analysis of the corresponding tri-(R)-MTPA ester in comparison with stereochemically defined synthetic samples. 相似文献
2.
《Tetrahedron: Asymmetry》2007,18(4):513-519
Total synthesis of (4R,5S,6E,14S)- and (4R,5S,6E,14R)-cystothiazoles F 3 was achieved from the chiral bithiazole-type primary alcohols [(S)- and (R)-4-ethoxycarbonyl-2′-(1-hydroxymethylethyl)-2,4′-bithiazoles 8], which were obtained based on the enzymatic resolution of racemic alcohol 8 and its acetate 9. From a direct comparison by means of chiral HPLC between natural cystothiazole F 3 and synthetic compounds [(4R,5S,6E,14S)- and (4R,5S,6E,14R)-cystothiazoles 3], natural cystothiazole F 3 was found to be a 33:67 diastereomeric mixture [(4R,5S,6E,14S)-3:(4R,5S,6E,14R)-3 = 33:67]. 相似文献
3.
Pravin L. Kotian 《Tetrahedron letters》2011,52(3):365-368
Imino sugar compound 3 was prepared by two alternative routes starting from ribose and d-serine. From d-serine (3R,4R,5R)-3,4-dihydroxy-5-(hydroxymethyl)-3-methylpyrrolidin-2-one was prepared in five steps in 50% overall yield, which was further converted into (2R,3R,4S)-2-(hydroxymethyl)-4-methylpyrrolidine-3,4-diol in three steps in 23% overall yield. 相似文献
4.
《Tetrahedron》1986,42(6):1763-1768
(-)-(1S,3S,5R,6S,8R,10R)-Trishomocubanethanoic acid (5) of known absolute configuration and absolute rotation was converted into (+)-(1S,3S,5S,6S,8R,10R)-2-bromoethynyl-D3-trishomocubane (27) of C3 symmetry. 1,3,5,7-Tetraethynyladamantane (22), with Td symmetry, was prepared from 1,3,5,7-tetrakis(hydroxymethyl)adamantane(13). Coupling of the C3-component 27 with the Td component 22 was successfully accomplished by Chodkiewicz and Cadiot's procedure providing (+)-1,3,5,7-tetrakis[2-(1S,3S,5R,6S,8R,10R)-D3-trishomocubanylbuta-1,3-diynyl]adamantane(4) whose highest attainable static and time-averaged dynamic symmetry are T and (C3)4 XXX T,respectively. 相似文献
5.
N. A. Ivanova Z. R. Valiullina O. V. Shitikova M. S. Miftakhov 《Russian Journal of Organic Chemistry》2006,42(11):1701-1705
Methyl (1S,2S,3R,4R)-2,3-isopropylidenedioxy-5-iodomethyl-2-tetrahydrofurylacetate prepared in two stages from D-ribose acetonide underwent a series of uncommon transformations under the treatment with bases providing the following different products depending on the base applied: methyl 3-(5-acetyl-2,2-dimethyl-1,3-dioxol-4-yl)propionate (DBU), methyl 2,3-isopropylidenedioxy-7-oxabicyclo[2.2.1]heptane-6-carboxylate (t-BuOK), methyl {(5R)-2,2-dimethyl-5-[(2R)-oxiranyl]-1,3-dioxolan-4-ylidene}propionate and methyl-(E)-3-{(4S,5R)-2,2-dimethyl-5-[(1R)-(2-oxiranyl)]-1,3-dioxolan-4-yl}-2-propenoate (t-BuOK and LDA). 相似文献
6.
Synthesis and Chirality of (5R, 6R)-5,6-Dihydro-β, ψ-carotene-5,6-diol, (5R, 6R, 6′R)-5,6-Dihydro-β, ε-carotene-5,6-diol, (5S, 6R)-5,6-Epoxy-5,6-dihydro-β,ψ-carotene and (5S, 6R, 6′R)-5,6-Epoxy-5,6-dihydro-β,ε-carotene Wittig-condensation of optically active azafrinal ( 1 ) with the phosphoranes 3 and 6 derived from all-(E)-ψ-ionol ( 2 ) and (+)-(R)-α-ionol ( 5 ) leads to the crystalline and optically active carotenoid diols 4 and 7 , respectively. The latter behave much more like carotene hydrocarbons despite the presence of two hydroxylfunctions. Conversion to the optically active epoxides 8 and 9 , respectively, is smoothly achieved by reaction with the sulfurane reagent of Martin [3]. These syntheses establish the absolute configurations of the title compounds since that of azafrin is known [2]. 相似文献
7.
Pravin L. Kotian 《Tetrahedron letters》2005,46(19):3327-3330
A concise stereoselective synthesis of an imino sugar, (3S,4R)-4-(hydroxymethyl)pyrrolidin-3-ol from (S)-diethylmalate has been developed in five steps and in overall yield of 28%. 相似文献
8.
Peddikotla Prabhakar Singanaboina Rajaram Yenamandra Venkateswarlu 《Tetrahedron: Asymmetry》2009,20(15):1806-1808
An Oppolzer anti-aldol approach for the synthesis of the sex pheromone (3S,5R,6S)-3,5-dimethyl-6-isopropyl-3,4,5,6-tetrahydropyran-2-one is reported. 相似文献
9.
《Tetrahedron: Asymmetry》2006,17(20):2876-2883
An efficient and a convenient enantioselective synthesis of (3R,4S)-3-methoxy-4-methylaminopyrrolidine has been carried out by a lipase-mediated resolution protocol. This method describes the preparation of (±)-1-Cbz-cis-3-azido-4-hydroxypyrrolidine starting from commercially available diallylamine followed by ring-closing metathesis (RCM) via SN2 displacement reactions. Pseudomonas cepacia lipase immobilized on diatomaceous earth (Amano PS-D) provides (3R,4S)-11 and (3S,4R)-12 in an excellent enantiomeric excess. 相似文献
10.
The synthesis of (1R,2S)- and (1S,2R)-1-amino-2-(hydroxymethyl)cyclopropanephosphonic acids was accomplished using different strategies. The (1R,2S)-stereoisomer could be efficiently obtained by the cyclopropanation of ethyl diethoxyphosphorylacetate with the cyclic sulfate derived from (S)-3-benzyloxy-1,2-propandiol as a key step. The (1S,2R)-stereoisomer was synthesized from a readily available (1S,5R)-3-oxabicyclo[3.1.0]hexan-2-on-1-phosphonate. 相似文献
11.
(+)-(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
12.
G. Yu. Ishmuratov A. V. Bannova E. R. Latypova R. R. Muslukhov A. A. Smol′nikov R. F. Talipov 《Chemistry of Natural Compounds》2012,48(5):789-790
A modified stereospecific synthesis of potentially biologically and pharmacologically active methyl (1R,2R,3E,5R)-3-(hydroxyimino)-5-methyl-2-(1-methylethyl)cyclohexanecarboxylate from (R)-4-menthen-3-one was developed using sequential 1,4-conjugate addition of Norman reagent catalyzed by CuI?CBF3?Et2O?CCuCl2 and ozonolysis?Creduction of the intermediate (R,R,R)-vinylmenthone by hydroxylamine hydrochloridein MeOH. 相似文献
13.
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
14.
(+)-(1S, 3S, 6S, 8S)- and (?)-(1R, 3R, 6R, 8R)-2,7-dioxa-twista-4,9-diene. A synthesis and the determination of the sense of chirality of (+)-(1S, 3S, 6S, 8S)- and (?)-(1R, 3R, 6R, 8R)-2,7-dioxa-twista-4,9-diene ((+)- 5 and (?)- 5 , respectively) is described. 相似文献
15.
《Tetrahedron: Asymmetry》1999,10(2):207-211
The reaction of 2-lithiophenyldiphenylphosphine with phosphorus trichloride afforded the new unsymmetric phosphine, dichloro(2-diphenylphosphinophenyl)phosphine (4). Condensation of 4 with (a) (2R,3R)-dimethyl tartrate or (b) (S)-binaphthol in the presence of triethylamine gave new chiral phosphine-phosphonite ligands, (2R,3R)-[2-(2′-(diphenylphosphino)phenyl)-4,5-bis(carbomethoxy)-1,3,2-dioxaphospholane] ((2R,3R)-5) and (S)-[2-(diphenylphosphino)benzene][1,1′-binaphthalen-2,2′-diyl]phosphonite] ((S)-6). The analogous reaction of 4 with (1R,2S)-ephedrine using N-methylmorpholine as the base, gave [2-(2′-(diphenylphosphino)phenyl)-3,4-dimethyl-5-phenyl-1,3,2-oxazaphospholidine] (7) as a 95:5 mixture of diastereoisomers. 相似文献
16.
Robert Glaser Itay Adin David Ovadia Ernestine Mendler Marc Drouin 《Structural chemistry》1995,6(3):145-156
Single-crystal X-ray diffraction analysis was used to determine the structure of a racemic diastereomer of the agricultural fungicide propiconazole [1-(2-(2,4-dichlorophenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole] and of two by-products (a symmetrical 1,3,4-triazole racemic-constitutional isomer and a propiconazole ditriazole analogue). All three crystalline racemic-diastereomers had (2R,4S)/(2S,4R)-stereochemistry in which then-propyl group was observed in atrans-to-phenyl disposition. Propiconazole (2R,4S)/(2S,4R)-diastereomer gives crystals belonging to the monoclinic space group P21,/a, and, at 293 K,a=8.1192(3),b=18.9769(6),c=10.7137(4) å,Β=99.765(3)?,V=1626.8(1) å3, Z=4,R(F)=0.060, andR w(F)=0.058. The constitutional isomer by-product (2R,4S)/(2S,4R)-1-(2-(2,4-dichlorophenyl)-4-n-pro-pyl-1,3-dioxolane-2-yl-methyl)-1-H-1,3,4-triazole gives crystals belonging to the monoclinic space group P21/n, and, at 293 K,a=11.1763(6),b=10.7716(4),c=14.5804(8) å,Β=107.445(4)?,V=1674.6(1) å3, Z=4,R(F)=0.043, andR w(F)=0.043. The ditriazole byproduct (2R,4S)/(2S,4R)-1-(2-(2-chloro-4-(1,2,4-triazole-1-yl)phenyl)-4-n-propyl-1,3-dioxolane-2-yl-methyl)-1-H-1,2,4-triazole gives crystals belonging to the triclinic space groupP¯ 1, and, at 193 K,a=5.3329(8),b=8.3738(7),c=20.240(2) å, α=84.213(6)?,Β=87.20(1)?,γ=86.23(1)?,V=896.5(2) å3, Z=2,R(F)=0.046, andR w(F)=0.051. The presence of both propiconazole (2R.4S)- and (2S,4R)-enantiomers enables the formation of a crystalline racemic modification, while the diastereomeric propiconazole (2R,4R)- and (2S,4S)-enantiomers are viscous oils. In the absence of its enantiomorphic partner, the propiconazole (2R,4S)- or (2S,4R)-enantiomers remain as viscous oils rather than form chiral crystals. 相似文献
17.
Epoxidation of (?)-(1R,2R,4R)-2-endo-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-exo-yl acetate ((?)-5) followed by saponification afforded (+)-(1R,4R,5R,6R)-5,6-exo-epoxy-7-oxabicyclo[2.2.1]heptan-2-one ((+)-7). Reduction of (+)-7 with diisobutylaluminium hydride (DIBAH) gave (+)-1,3:2,5-dianhydroviburnitol ( = (+)-(1R,2R,3S,4R,6S)-4,7-dioxatricyclo[3.2.1.03,6]octan-2-ol; (+)-3). Hydride reductions of (±)-7 were less exo-face selective than reductions of bicyclo[2.2.1]heptan-2-one and its derivatives with NaBH4, AlH3, and LiAlH4 probably because of smaller steric hindrance to endo-face hydride attack when C(5) and C(6) of the bicyclo-[2.2.1]heptan-2-one are part of an exo oxirane ring. 相似文献
18.
《Tetrahedron: Asymmetry》1998,9(8):1395-1407
Two different methods for preparing the thiazole analogue 3 of the biologically active compound (1R,2S,3R)-2-acetyl-4(5)-(1,2,3,4- tetrahydroxybutyl)imidazole 1 are reported. 相似文献
19.
《Tetrahedron: Asymmetry》2007,18(23):2787-2790
The enantioselective synthesis of (R)- and (S)-1-amino-3-hydroxypropylphosphonic acid, the phosphonate analogues of (S)- and (R)-homoserine, has been accomplished in four steps and good overall yield starting from diethyl (3R,5R)- or (3S,5S)-5-(hydroxymethyl)-2-[(S)-1-phenylethyl]isoxazolidinyl-3-phosphonate, respectively. 相似文献
20.
《Tetrahedron: Asymmetry》2005,16(16):2799-2809
Enantiopure 1,1′-ethylenedipyrrolidines possessing 3,4-disubstitution have been prepared from esters of l-(+)-tartaric acid. Although diacylation routes via the diacetoxypyrrolidin-2,5-diones were problematic, N,N-dialkylation protocols proved to be reliable and led to the synthesis of (3S,3S′,4S,4S′)-1,1′-ethylenedipyrrolidine-3,3′,4,4′-tetraol, (3R,3′S,4R,4′S)-3,4-diamino-1,1′-ethylenedipyrrolidine-3′,4′-diol and (3R,3′R,4S,4′S)-3,3′-diamino-1,1′-ethylenedipyrrolidine-4,4′-diol. The tetraol possesses a crystal structure that exhibits an unusual zig-zag intermolecular pattern comprising a network of hydrogen bonds involving the terminal hydroxyl groups and a nitrogen atom of one of the pyrrolidine rings. 相似文献