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1.
Jack E. Baldwin Robert M. Adlington Bernard J. Rawlings Richard H. Jones 《Tetrahedron letters》1985,26(4):485-488
Practical procedures for the resolution of racemic modification of (1, 2)-and (1, 2)-1-amino-2-ethylcyclopropane-1-carboxylic acid ,,(1, 2)- and (1, 2)-1-amino-2-methylcyclopropane-1-carboxylic acid ,, and (1, 2)- and (1, 2)-1-amino-2-methylcyclopropane-1-carboxylic acid , are described; the structures as ,, and were confirmed by X-ray-crystallographic methods. 相似文献
2.
Julian Tirado-Rives Richard David Gandour Frank Rolf Fronczek 《Tetrahedron letters》1982,23(16):1639-1642
Syntheses of - and -[a,e]-dibenzo-7,10,13-trioxacyclotrideca-1,3,5-triene, (n=1) and - and -[e,a]-dibenzo-7,10,13,16-tetraoxacyclohexadeca-1,3,5-triene, (n=2) are described and the X-ray structure of E- (n=1) is reported. 相似文献
3.
-() and -1,3-Butadienylcyclobutane (), all--1-(1 ,3-butadieny1 )-2- vinylcyclobutane (), and all--1,2-bis(1,3-butadienyl)cyclobutane () have been prepared from readily available starting materials, and pyrolyzed to various cyclohexenes. 相似文献
4.
Lithiation of both ()- and ()-3-trimethylsilyl-2-propenyl ,-diisopropyl carbamate 2 affords the (2) -lithium compound 3. Aluminium- or titanium-mediated addition to aldehydes, 4 gives (1)-(3*4*)-enol carbamates 7. A stereospecific Peterson elimination (borontriflouride- or base-mediated) introduces the second double bond either with (3)- or with (3)-configuration. So just by reagent selection for each of the two steps, (1,3)-, (1,3)-, (1,3)-, or (1,3)- dienes 8 - 11, respectively, are prepared with stereoselectivities up to > 99.7% 相似文献
5.
The reaction of both - and -2-amino-1-(1-phenylvinyl)- cyclopentanols with aldehydes affords -2-alkyl--3a-aryl-4-oxo-octahydro indoles stereoselectively. 相似文献
6.
The stereoselective synthesis of 3-O-methyl-7α--toluenesulphonyl-8α, 9α, 14β-estradiol () and its 11-oxo derivative () thermolysis of 1β--butoxy-2α-[2-(4-methoxybenzocyclobutenyl)ethyl]-2β-methy1-3α-[2-(-toluenesulphonyl)ethenyl] cyclopentane () and its oxo derivative (), which were derived from condensation product () of optically active aldehyde () and 1-cyano-4-methoxybenzocyclobutene through and to selenides and , is described. 相似文献
7.
Isao Kitagawa Hirotaka Shibuya Hiromichi Fujioka Yoshio Yamamoto Akiharu Kajiwara Kunihiro Kitamura Ayako Miyao Toshio Hakoshima Ken-ichi Tomita 《Tetrahedron letters》1980,21(20):1963-1966
Acid treatment of (IR, 3S,1′S)-1-(1′,2′-Epoxyethyl)-1,2,2-trimethyl-3-acetoxymethyl-cyclopentane ) has been shown to yield three products (, , ), among which and are 1-oxa-bicyclo[3.3.0]octane derivatives formed successive methyl migrations followed by an oxorane ring closure. 相似文献
8.
Iodine-mediated cyclization of (Z)- and (E)-{=D}-ribohept-2-enonates and gave exclusively the β-ribofuranose and α-ribofuranose derivatives and , respectively. Cyclization of the (Z)- and (E)-2-heptene-1-ol derivatives and gave ribofuranose products ( and ) and a ribopyranose (), respectively. 相似文献
9.
- The corresponding - and -methyl- and -benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines were synthesized from - and -methyl and-benzyl-2- aminomethyl-1-cyclohexanols , from - and -methyl- and benzyl -2-hydroxymethyl-1-cyclohexylamines by reaction with formaldehyde. The aminoalcohols and were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of -benzyl--4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate . determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy. 相似文献
10.
Direct chlorination of 2-(2H-hexafluoropropyl)-tetra- hydrofuran gave high yield of 2-(2-chlorohexafluoropropyl)- pentachloro-2,5-dihydrofuran . Bromination of gave very complex mixture of products, from which three compounds, . 2-bromo-5-(2H-hexafluoropropyl)-furan , 3-bromo-5-(2H-hexafluoropropyl)-furan , and 2,4-dibromo-5-(2H-hexafluoropropyl)furan were isolated. Exchange fluorination of with dry KF at 240 – 300° led to a stepwise substitution of fluorines for chlorines to give mixtures of chloro-fluoro-2-(2-chlorohexafluoropropyl)-dihydrofurans ,, and , together with small amounts of 2-(2-chlorohexafluoropropyl)-3,4,5-trichlorofuran .Exchange fluorination of 3,4-dihalo-2,2,5,5-tetrafluoro- 2,5-dihydrofurans and led to a substitution of fluorine for one vinylic halogen to give 3-halo-2,2,4,5,5-pentafluoro-2,5-dihydrofurans and in good yields.Compounds – were characterised by n.m.r., m.s., and i.r. spectroscopy and elemental analysis. 相似文献
11.
Treatment of -alkylacetylenes, generated from 1--1- alkenephosphonates, with silyl enol ethers in the presence of a catalytic amount of tetrabutylammonium fluoride gives good yields of -alkyl-substituted propargyl alcohols or 4-(1--alkylidene)-1,3-dioxolane derivatives, the latter being converted to tie corresponding α-hydroxy ketones. 相似文献
12.
Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′, 2, 2″, 5, 6)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′, 2, 5, 6)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran. 相似文献
13.
The cycloaddition of α,β-epoxyaldehydes or ketones () with the ketene acetal MeHC=C(OMe)2 () gives epoxyoxetanes () in high yields. Without isolation they can be transformed into 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones () via the epoxy esters and trihydroxy esters (). The lactones appear to be valuable precursors for the synthesis of 5-(1-hydroxyalkyl)-3-methyl-2-5H-furanones () and 3-methyl-5-ylidene-2-5H-furanones () 相似文献
14.
3,4-Tetramethylene- and -3,4-diethyl-1,2-dioxetane ( and ) were prepared and characterized (for - Ea = 22.5 kcal/mole, log A = 12.8; for - Ea = 24.5 kcal/mole, log A = 13.1). 相似文献
15.
G.B. Marini-Bettolo M. Nicoletti I. Messana C. Galeffi J.D. Msonthi W.A. Chapya 《Tetrahedron》1985,41(4):665-670
From rhizome of two diglucosides were isolated: hypoxoside, (1), and a new one, the 0,0-β,β-di-D-glu- copyranoside of 1-(4hydroxyphenyl)-3-(4hydroxyphenyl)-1,4-pen- tadiene, (2), named nyasoside. 相似文献
16.
On the basis of their 1H n.m.r. spectra it is concluded that vinyl alcohol and -1-propenol exist mainly in the -conformation and that -1-propenol and 2-methyl-1-propenyl exist mainly in the conformation. 相似文献
17.
The - and -2-amino-4-cyclohexene-1-carboxylic acids and react with imidates to give the condensed-skeleton, bicyclic - and -pyrimidin-4-ones and . The amino acids and were reduced to the -and -1, 3-aminoalcohoIs and , which were cyclized by means of imidates to the bicyclic tetrahydro-4-3,1-benzoxazines and , or were converted, the corresponding carbamates and into the tetrahydro-4-3,1-benzoxazin-2(1)-ones and . The 2-thioxo analogues and were prepared by cyclization of the dithiocarbamates obtained from the aminoalcohols and by treatment with carbon disulphide. The -aminoalcohol and its saturated analogue reacted with -chlorobenzaldehyde to furnish the hexahydro and octahydro-4-3,1-benzoxazine , respectively. 1H and 13C NMR studies showed that, similarly to the earlier-investigated analogues containing oxygen or unsubstituted nitrogen at position 1, the synthesized isomrs , , and occurred as the preferred conformer in the heterocyclic twist inverse form of -inside type ( C6-N bond) (B). In the isomers containing a saturated C-2 atom ( and ), H-2 and H-6 are in relative positions. 相似文献
18.
A stereospecific synthesis of acetyl--valyl-detoxininolactone has been performed and the absolute stereochemistry of detoxinine has been revised to (2, 3, 1′)-2-(2′-carboxy-1′-hydroxyethyl)-3-hydroxypyrrolidine. 相似文献
19.
A 4′-ene derivative of kanamycin B () was derived from the epoxide () by oxidative elimination of the 4′-phenylseleno group into the allylic alcohol (). The title compound, 0-(2,6-diamino-2,4,6-trideoxy-β-L-arabino-hexopyranosyl)-(1→4)-0-[3-amino-3-deoxy-α-D-glucopyranosyl-(1→6)]-2-deoxystreptamine () was obtained from by stereospecific hydrogenation followed by removal of the masking groups, changing the D-sugar moiety of the 4-0-glycoside portion into an L-sugar. 相似文献
20.
Felix H. Cano Concha Foces-Foces Manuel Bernabe Jesus Jimenez-Barbero Manuel Martin-Lomas Soledad Penades-Ullate 《Tetrahedron》1985,41(18):3875-3886
X-Ray and 1H N.M.R. studies on pyranoid rings 1,2--fused to dioxolane rings in acetylated -gluco- and --galactopyranose derivatives demonstrate that the configuration of the dioxolane ring influences the conformation of the pyranoid ring in the -gluco but not in the -galactopyranose series. The crystal structure of 3,4,6-tri--acetyl-1,2--(R)--(l-cyano-ethylidene)-α--glucopyranose () and 3,4,6-tri--acetyl-1,2--()-(1-cyano-ethylidene)-α--galactopyranose ()have been determined by X-ray analysis. Lattice parameters for are a=20.6021 (11), b=8.0438 (2), c=5.5541 (1) Å and β= 95.588 (3)° for a cell with P21 symmetry. These parameters for are a=20.3361 (7), b=10.0907 (2), c=18.9115 (5) Å, β =112.399 (2)°, C2, with two crystallographycally independent molecules. The conformation of the pyranoid ring in both compounds can be described as flattened 4C1 and that of the dioxolane ring as distorted E1. The importance of the torsion angles for describing problems of configuration is remarked and the use of relative configurational angles is stressed. The 1H N.M.R. spectra of and and 3,4,6-tri--acetyl-1,2-O-(S)- and (R)-ethylidene-α--glucopyranose ( and ), 3,4,6-tri-O-acetyl--1,2-O-(S)- and ()-ethylidene-α--galactopyranose ( and ), and 3,4,6-tri--acetyl-1,2--()-and ()-benzylidene-α--glucopyranose ( and ) have been analyzed by using iterative computer methods and N.O.E. measurements. The results indicate that the major solution conformation of the pyranoid ring of the derivatives in the -gluco series , and may be described as flattened 4C1 and that of and as 25. The major solution conformation of the pyranoid ring in all compounds in the -galacto series (,,,) may be described as flattened 41. 相似文献