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1.
Reaction of mucochloric and mucobromic acid with (ethoxycarbonylmethylene) triphenyl-phosphorane affords the ethyl ester of (2, 4 -4,5-dichloro- and (2, 4) -4, 5-dibromo-2,4-pentadienoic acid respectively; in the latter case ethyl (2 -5-bromo-2-penten-4-ynoate is formed concomittantly. 相似文献
2.
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
3.
Masaru Inage Haruyuki Chaki Shoichi Kusumoto Tetsuo Shiba 《Tetrahedron letters》1981,22(24):2281-2284
1-α-Monophosphate (), 4′-monophosphate (), and 1-α, 4′-diphosphate () of 6-0-(2-deoxy-2-tetradecanoylamino-6-0-tetradecanoyl-β-D-glucopyranosyl) -2-deoxy-2-tetradecanoylamino-3, 4-di -0-tetradecanoyl-D-glucopyranose were prepared in order to elucidate the role of phosphate moieties in endotoxic activity of lipid A. 相似文献
4.
Tetsuji Kametani Hiroo Matsumoto Toshio Honda Mitsuo Nagai Keiichiro Fukumoto 《Tetrahedron》1981,37(15):2555-2560
A stereoselective synthesis of des-A-ring steroids and has been achieved by an intramolecular cycloaddition of 3-isopropenyl-5-(4-methoxybenzocyclobutenyl) pentan-2-one-2-ethylene ketal and 1-(4-methoxy-benzocyclobutenyl)-4-methylpent-4-en-3-ol , respectively. 相似文献
5.
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
6.
2-Hydroxybenzoic acid heated with 2,4 - bis(4 - methoxyphenyl) - 1,3,2,4 - dithiadiphosphetane - 2,4 -disulfide, 1, gave 2 - (p - methoxyphenyl) - 4 - 1,3,2 - benzoxathiaphosphorin - 4 - one 2 - sulfide, 3, and its thio-analogue, 4, while its ethyl or phenyl esters gave 4 as the sole product. 2 - Mercaptobenzoic acid and its ethyl ester when heated with 1 produced 3 - 1,2 - benzodithiole - 3 - one, 8, 3 -1,2 - benzodithiole - 3 - thione, 9, and 2- (p - methoxyphenyl) - 4 - 1,3,2 - benzodithia - phosphorin - 4 - one 2 - sulfide, 10. The reaction of 2 -aminobenzoic acid with 1 gave 1,2 - dihydro - 2 - (p - methoxyphenyl) - 4 - 3,1,2 - benzoxaphosphorin - 4 - one 2 - sulfide, 12. Reactions of 1 with methyl 2 - aminobenzoate and 2 - aminobenzamides are described. Mechanistic considerations for the formation of the heterocyclic phosphorus compounds are presented. 相似文献
7.
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
8.
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
9.
T. Tanaka N. Okamura K. Bannai A. Hazato S. Sugiura K. Manabe S. Kurozumi 《Tetrahedron letters》1985,26(45):5575-5578
(5)-Prostaglandin E2 methyl ester was synthesized from ()-4--butyldimethylsiloxy-2-cyclopentenone by 2-alkenyloxycarbonylation of the organocopper conjugate-addition adduct followed by intramolecular palladium-catalyzed decarboxylative 2-alkenylation. A ()-2-butenylated cyclopentanone derivative was obtained from either 2-[()- or ()-2-butenyloxy-carbonyl]cyclopentanone derivative under the similar reaction condition. 相似文献
10.
Solid potassium hydroxide dehydrofluorinates 2,2-bis-(trifluoromethyl)-3,4-difluoro-oxetan to 3-fluoro-4,4-bis-(trifluoromethyl)-2-oxete (59%), 2-pentafluoroethyl-3,4-difluoro-oxetan to 2-tetrafluoroethylidene-3,4-difluoro-oxetan, and -2-heptafluoro-n-propyl--3,-4-difluoro-oxetan to ()-2-hexafluoro-n-propylidene- -3,4-difluoro-oxetan. Factors which affect these reactions are discussed. 相似文献
11.
Three fungal metabolites with a common structural feature as prenylated phenols were synthesized in their naturally occurring and optically active forms: ascochlorin [(2',4',1',2',6')-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[5'-(1',2',6'-trimethyl-3'-oxo-cyclohexyl)-3'-methyl-2', 4'-pentadienyl] benzaldehyde], ascofuranone [(2',6',1')-(-)-5-chloro-2, 4-dihydroxy-6-methyl-3-[7'-(3',3'-dimethyl-4'-oxo-2'-oxacyclopentyl)-3',7'-dimethyl -2', 6'-heptadienyl] benzaldehyde] and ascofuranol [(2',6',1',4')-(-)-5-chloro-2,4-dihydroxy-6-methyl-3-[7'-(3', 3'-dimethyl-4'-hydroxy-2'-oxacyclopentyl)-3', 7'-dimethyl-2',6'-hepta-dienyl]benzaldehyde ]. (+)-Ascofuranone and (+)-ascofuranol were also synthesized. By the present synthesis the absolute configuration of the natural (-)-ascofuranol was established as (1',4'). 相似文献
12.
E.G. Frandsen 《Tetrahedron》1977,33(8):869-873
The reaction of 4- and 5-aryl-3-methylthio-1,2-dithiolylium iodides with 4-hydroxy-6-methyl-2-pyran-2-one and 4-hydroxycoumarin has been studied. 4-Substituted salts yielded 3-aryl-7-methyl-2-thioxo-2,5-pyrano [3,2-c]pyran-5-ones and 3-aryl-2-thioxo-2H,5H-pyrano[3,2-c]benzo[e]pyran-5-ones, respectively, whereas 5-substituted salts gave rise to 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-6-methyl-2-pyran-2,4-diones and 3-(5′-aryl-1′,2′-dithiol-3′-ylidene)-2-benzo [b]-pyran-2,4-diones. 相似文献
13.
Condensation of 3-fluoro-2-butanone () with alkyl diethylphosphonoacetates () gave alkyl 4-fluoro-3-methyl-2-pentenoates (). Addition of bromine yielded alkyl-2,3-dibromo-4-fluoro-3-methylpentanoates () which were dehydrobrominated to alkyl 2-bromo-4-fluoro-3-methyl-2- pentenoates (). Since these compounds could not be hydrogenated to the desired alkyl 2-bromo-4-fluoro-3-methylpentanoates (), another route was taken. The esters were hydrogenated to alkyl 4-fluoro-3- methylpentanoates () which were converted to their carbanions. Treatment with bromine gave esters , and iodine gave alkyl 4-fluoro-2-iodo- 3-methylpentanoates (). Esters and were converted to alkyl 2-azido-4-fluoro-3-methylpentanoates () whose hydrogenation gave alkyl 2-amino-4-fluoro-3-methylpentanoates (). Hydrolysis afforded γ-fluoroisoleucine (). 相似文献
14.
-() 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
15.
Géza Stájer LászlÓ Mód Angela E. Szabó Ferenc Folöp Gábor Bernáth Pál Sohár 《Tetrahedron》1984,40(12):2385-2393
The -- amino acid with norbornene skeleton was converted into 2-aryvl---1,3-oxazin-4-ones -. These compounds, similarly to the isomers - studied by us earlier, undergo retrodiene decomposition under mild conditions to give 2-aryl-6-l,3-oxazin-6-ones (-) in 50-60% yield. The ratio of the decomposition rate constants of the tricyclic and -1,3-oxazin-4-ones, measured in toluene solution, is about 2. 相似文献
16.
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
17.
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
18.
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
19.
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
20.
The photoreactions of 4 and 2-pyridinecarbonitrile with cyclopentene carried out in acetone or in acetonitrile solutions lead, respectively, to 4-(2 cyclopentenyl)-pyridine and 2-(2 cyclopentenyl)pyridine . From 2-pyridinecarbonitrile a little amount of ketone is obtained. 相似文献