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1.
γ-Alkenyl-α,β,γ-trisubstituted-γ-butyrolactones (12-16) and γ-alkenyl-furofurandione derivatives (21-Z-24-Z; 21-E-24-E; 25-Z-28-Z; and 25-E-28-E) were successfully epimerized in high yield by a palladium catalyst. 相似文献
2.
An efficient and versatile synthesis of various congested pyridines 3a-h, 6a,b, 8a-n, 10a-g, and 16a,b, and (pyrimidin-4-yl)acetonitriles 13a-g has been delineated by base catalyzed ring transformation of suitably functionalized 2H-pyran-2-ones 1a-h, 5, 7, and 15 by formamidine acetate 2a, acetamidine hydrochloride 2b, S-methylisothiourea 9a, pyrazol-1-yl-carboxamidine 9b, and arylamidine hydrochloride 12 separately in the presence of powdered KOH in dry DMF. 相似文献
3.
Four new difluorinated tetra- and pentabromo BDE internal standards for GC-MS/GC-ECD analysis, 2F-BDE47, 2F-BDE85, 2F-BDE99 and 2F-BDE119, have been prepared in 98-99.0% purity, mainly by coupling of the new tribromodifluorophenols (19-21) and symmetrical bromodiphenyliodonium salts (8, 22). The four difluorinated BDEs showed promising properties as internal standards for quantitative BDE analysis. Tetra-, penta-, hexa- and hepta-brominated BDE reference standards, BDE75, BDE85, BDE138 and BDE183, were also prepared in 98.4-99.8% purity and characterised. 相似文献
4.
The reductive opening of substituted phthalans 6, 11, 12, 20, 21 and 28 with lithium and a catalytic amount of DTBB leads to the formation of corresponding functionalised organolithium intermediates 8, 15, 16, 23, 25 and 29+30 in a regioselective manner. The further reaction of these dianions with different electrophiles, mainly carbonyl compounds, gives the expected functionalised benzylic alcohols 9, 17, 18, 24, 26 and 31+32. The observed stereochemistry can be easily explained taking into account the values of the electron densities deduced by semiempirical PM3 calculations. 相似文献
5.
Saleh M. Al-Mousawi Moustafa Sherief Moustafa Mohamed Hilmy Elnagdi 《Tetrahedron letters》2009,50(46):6411-6413
Compounds 1a-d react with benzylidenemalononitrile 2 to yield dihydroaminopyridazines 3a-d and, in contrast, compounds 1e,f react with 2 under the same conditions to yield aminobenzenedicarbonitriles 8e,f compound 8e underwent intramolecular cyclization to phthalazine 9e. Compound 10e reacted with 2a to yield 11e. 相似文献
6.
Synthesis of methylenecyclopropane analogues of nucleoside phosphonates 6a, 6b, 7a and 7b is described. Cyclopropyl phosphonate 8 was transformed in four steps to methylenecyclopropane phosphonate 16. The latter intermediate was converted in seven steps to the key Z- and E-methylenecyclopropane alcohols 23 and 24 separated by chromatography. Selenoxide eliminations (15→16 and 22→23+24) were instrumental in the synthesis. The Z- and E-isomers 23 and 24 were transformed to bromides 25a and 25b, which were used for alkylation of adenine and 2-amino-6-chloropurine to give intermediates 26a, 26b, 26c and 26d. Acid hydrolysis provided the adenine and guanine analogues 6a, 6b, 7a and 7b. Phosphonates 6b and 7b are potent inhibitors of replication of Epstein-Barr virus (EBV). 相似文献
7.
Péter Csomós Lajos Fodor Gábor Bernáth Jari Sinkkonen Kirsti Wiinamäki 《Tetrahedron》2008,64(6):1002-1011
Quinoline analog 2-aryl-4H-3,1-benzothiazine derivatives 8-13, obtained by the condensation of o-aminobenzyl chloride 1 with substituted thiobenzamides 2-7, were transformed to azeto[2,1-a][3,1]benzothiazin-1-one derivatives 18-23a,b,c and 24d,e by reaction with the corresponding substituted acetyl chlorides 14-17 in the presence of triethylamine. The structures of the new molecules were determined by NMR spectroscopy and electron ionization (EI) mass spectrometry. The typical EI+ mass spectrometric fragmentations of 8-13 and 18-23a,b,c and 24d,e are discussed in detail. 相似文献
8.
Heat-sensitive thiophosphate protecting groups derived from the alcohol 4 or 10 have provided insights in the design of DNA oligonucleotide prodrugs. Indeed, functional groups stemming from the alcohol 9, 15, 16 or 22 may be applicable to thiophosphate protection of immunostimulatory CpG DNA motifs, whereas those originating from the alcohol 3, 5, 12, 13, 18, 20 or 22 offer adequate protection of terminal phosphodiester functions against ubiquitous exonucleases that may be found in biological environments. Functional groups derived from the alcohol 9, 15, 16, 19 or 23 are suitable for the protection of phosphodiester functions flanking the CpG motifs of immunomodulatory DNA sequences. 相似文献
9.
Takashi Kitayama Taketo YokoiYasushi Kawai Richard K HillMasanori Morita Tadashi OkamotoYukio Yamamoto Valery V FokinK.Barry Sharpless Seiji Sawada 《Tetrahedron》2003,59(26):4857-4866
Zerumbone (1) and its 6,7-epoxide (2) react with ammonia and dimethylamine regio- and stereospecifically, affording monoamines 3, 4, 7 and 8. All adducts have the same relative configuration at C2 and C3. The conjugate amination is thermodynamically controlled to arrive at a single diastereomer. At 15°C 7 reacts with cyanide to give aminonitrile 10 as the single product, while at 30°C, acyclic aminonitrile 11 is also formed. The reaction with 8 affords at 0°C bicyclic aminonitrile 12 of the asteriscane skeleton, while at 30°C or higher temperature, mixtures of 12 and tricyclic nitriles 13 and 13′ are obtained. Refluxing of 7, 8 and 10 in aqueous acetonitrile promotes scission of the zerumbone ring by retro-Mannich reaction to provide acyclic aldehydes 16-18, respectively. The dimethylamino group of 7, 8 and 10 is eliminated stereospecifically by Cope- and base-catalyzed eliminations to regenerate the zerumbone skeleton in the products 1, 2 and 21. Cope elimination of 12 results in a mixture of 13 and 13′ by deaminative transannular etherification. 相似文献
10.
4-Iodoanisoles 3a,b, 3d and 4-bromoanisoles 4a-d were readily obtained. An extreme steric hindrance precluded obtaining 3c. Catalytic borylation of 3a,b, 3d followed by hydrolysis of boronic ester 26a,b, 26d easily provided the boronic acids 5a,b, 5d. Compounds 5a and 5d were also synthesised, starting from 4a and 4d, by halogen/metal exchange. Because of a too important steric hindrance, this last reaction failed with 4c and 4b led to the unexpected but stable boronic ester 6. The final obtaining of 5b required a strongly basic hydrolysis with heating. 相似文献
11.
Tetsuro Ito Toshiyuki TanakaMunekazu Iinuma Ibrahim IliyaKen-ichi Nakaya Zulfiqar AliYoshikazu Takahashi Ryuichi SawaYoshiaki Shirataki Jin MurataDedy Darnaedi 《Tetrahedron》2003,59(28):5347-5363
Five new resveratrol oligomers; pauciflorols A-C (1-3), isovaticanols B (6) and C (8), and three new oligostilbene glucosides; pauciflorosides A (11), B (13), C (14), were isolated from the stem bark of Vatica pauciflora (Dipterocarpaceae) together with known 17 resveratrol oligomers (4, 5, 7, 9, 10, 12 and 15-25) and bergenin (26). The structures of isolates were established on the basis of detailed spectroscopic analysis. The typical and characteristic spectral properties of some resveratrol oligomers were also discussed. 相似文献
12.
Synthesis of methylene-2-ethynylcyclopropane analogues of nucleosides 12a, 12b, 13a, and 13b is described. Ethyl methylenecyclopropane carboxylate 14 was hydroxymethylated to give alcohol 15, which was reduced to diol 16. Selective protection with tert-butyldimethylsilyl group gave derivative 17, which was oxidized to aldehyde 18. Wittig reaction with CBr4 gave dibromoalkene 19. Elimination of both bromine atoms afforded methylene-2-ethynylcyclopropane 20. Bromoselenenylation using N-bromosuccinimide and diphenyldiselenide gave intermediate 21. Alkylation of adenine and 2-amino-6-chloropurine with 21 provided the Z,E-isomeric mixtures 22a and 22c. Oxidation afforded selenoxides 23a and 23c. Mild thermolysis furnished methylenecyclopropanes Z-24a, E-24a, and 24c. Deprotection and separation of Z,E-isomers gave adenine analogues 12a and 13a, and 2-amino-6-chloropurine intermediates 12c and 13c. Hydrolytic dechlorination of 12c and 13c afforded guanine analogues 12b and 13b. Adenine Z-isomer 12a inhibits replication of Epstein-Barr virus through its cytotoxicity. The E-isomer 13a is a substrate for adenosine deaminase. 相似文献
13.
Ashraf A Abbas 《Tetrahedron》2004,60(7):1541-1548
The 13-hydroxy macrocycles 7a-d were prepared in 40-50% yields by the condensation of 1,ω-bis(4-amino-1,2,4-triazol-3-ylsulfany)alkanes 2a-d with 1,3-bis(2-formyphenoxy)-2-propanol (9). Acylation of 7a-d with 2-chloroacetylchloride gave the corresponding esters 11a,b. Amination of 11a,b with different amines in acetone furnished exclusively the target lariat macrocycles 12a,b and 13 in 60-70% yields. Reaction of 2 equiv. of the macrocycles 11a,b with 1 equiv. of piperazine afforded the novel bis macrocyles 14a,b in 50-60% yields. Reduction of 7a-d with NaBH4 afforded the corresponding 13-hydroxyazathia crown ethers 15a-d in 65-70% yields. 相似文献
14.
Seven new alkaloids, named as 1,9-epoxy-9a-hydroxystenine (1), tuberostemoline A (2), tuberostemoline B (3), tuberostemoninol C (4), oxotuberostemonine A (5), the mixture of bisdehydrotuberostemonine D (6), and bisdehydrotuberostemonine E (7), together with four known alkaloids neotuberostemonine (8), sessilifoline B (9), stemoxazolidinone F (10), and tuberostemoninol A (11), were isolated from the roots of Stemona tuberosa. The structures of 1–7 were elucidated through extensive spectroscopic analysis, and the relative configurations of 1–6 and 8 were further confirmed by X-ray crystallographic data. Compounds 8, 9 and the mixture of 6 & 7 exhibited potential acetylcholinesterase (AChE) inhibitory activities. 相似文献
15.
Martin G. Banwell Matthew T. Jones David W. Lupton Jayanta K. Ray 《Tetrahedron》2010,66(47):9252-9262
The Pd[0]-catalyzed Ullmann cross-coupling of o-nitrohaloarenes 1a-e with the brominated heterocycles 2a-f delivers the expected products 3a-j in good to excellent yields. The reductive cyclization of such products, as well as N-acyl derivatives 3k, l, and m, has been investigated and provided the C-3 mono-substituted oxindoles 5a-d, f, g, k, and m, the direct reduction products 4i and j or indole 5l. 相似文献
16.
tert-Butyldimethylsililoxy-2-aza-1,3-butadienes react with 2H-azirine 3 leading to Diels-Alder cycloadducts in moderate yields. The reactions are endo- and regioselective with the azirine being added by its less hindered face. There is only one product in the case of 1b, 4b. There are two isomers (4 and 5) from 1a, 1c and 1d. A different result was obtained with the diene 1e. Diene 1e formed products 4e and 8. Some of compounds 4 and 5 have been hydrolysed leading to functionalised aziridines 7. Compound 8 gave aziridine 9. 相似文献
17.
Shigeki Sano 《Tetrahedron letters》2005,46(16):2883-2886
α-Alkynyl-α-ethoxycarbonyl cyclopentanones 1a-c and cyclohexanones 2a-c were readily synthesized by the reaction of ethyl 2-oxocyclopentanonecarboxylate 6 and ethyl 2-oxocyclohexanonecarboxylate 7 with alkynyllead triacetates 5a-c obtained from lithium acetylides 4a-c and lead tetraacetate. Treatment of 1a-c and 2a-c with 1 N KOH in THF or with n-Bu4N+OEt− in EtOH and THF gave the corresponding conjugated allenyl esters 8a-c, 9a-c, 10a-c, and 11a-c in good to excellent yields, respectively. 相似文献
18.
Pheromonal triacylglycerols and their analogs, 1A, 1B, 2A, 2B, 3A, 3B, and 3C, of male Drosophila fruit flies were synthesized and analyzed by GC–MS. Their GC retention times were found to be a reliable measure to analyze and identify these triacylglycerols with acetyl, oleoyl and tigloyl groups, although the stereo- and regioisomers of 1 (1A and 1B), 2 (2A and 2B), and 3 (3A, 3B, and 3C) could not be distinguished from each other by MS alone. 相似文献
19.
Phytochemical investigations on the organic extracts of the leaves of Suregada multiflora have led to the isolation of ten tetracyclic diterpene lactones 1-10, members of a rare class of abiatene diterpene lactones. Compounds 1-5 were found to be new. The structures of gelomulides F (11), D (12) and E (13) were revised on the basis of 2D NMR and X-ray diffraction evidences. Compounds 1 and 2 contain an epoxy linkage between C-8 and C-14, whereas compounds 3-5 were identified as 8,14-dihydroxy analogues of diterpene lactones. The stereochemical assignments in new compound 1 are based on X-ray diffraction analysis. Compounds 6 and 7 were identified as the known gelomulides A, G. The structures of compounds 7-9 were unambiguously confirmed by X-ray diffraction analyses. 相似文献
20.
I-Tzu WuPei-Yi Chaing Wen-Jung ChangHwo-Shuenn Sheu Gene-Hsiang LeeChung K. Lai 《Tetrahedron》2011,67(38):7358-7369
The synthesis, mesomorphic behavior, and optical properties of two new series of metal complexes 1a,b-M (M=Pd, Cu, Zn) derived from benzoxazoles 2a,b are reported. The crystal and molecular structures of mesogenic 5-decyloxy-2-(6-decyloxybenzooxazol-2-yl)phenol and nonmesogenic bis[5-octyloxy-2-(6-octyloxybenzooxazol-2-yl) phenol]Pd(II) were determined by means of X-ray structural analysis. Two benzoxazoles 2a exhibited monotropic SmA phases, and all benzoxazoles 2b were nonmesogenic. On the other hand, metal complexes 1a-M exhibited distinctly different mesomorphism from complexes 1b-M. Complexes 1a-Pd formed SmC phases; complexes 1a-Cu and 1a-Zn formed crystal phases. In contrast, complexes 1b-Zn exhibited columnar phases, and complexes 1b-Cu and 1b-Pd were nonmesogenic. The difference of the mesomorphism in 1a-M and 1b-M was probably attributed to the geometry and/or the overall molecular shape created by 2a and 2b. The electronic configuration of metal ion might play an important role in forming the mesophases. The fluorescent properties of these compounds were also examined. 相似文献