| 1. |
- Bergman, Jan, et al.
(författare)
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Studies of the reactions between indole-2,3-diones (isatins) and 2-aminobenzylamine
- 2003
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Ingår i: Tetrahedron. - 0040-4020 .- 1464-5416. ; 59:7, s. 1033-1048
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Tidskriftsartikel (refereegranskat)abstract
- Reflux of equimolecular amounts 2-aminobenzylamine and isatins in acetic acid produced indolo[3,2-c]quinolin-6-ones in good yields. A proposed mechanism involving initial formation of a spiro compound is given. This isolable intermediate subsequently rearranges via a sequential isocyanate ring opening and a cyclisation process to a urea derivative which finally cyclized to the indolo[3,2-c]quinolin-6-ones. The urea derivative could be prepared separately and cyclized selectively to indolo[3,2-c]quinolin-6-one. Reaction of N-acetylisatin with 2-aminobenzylamine at room temperature yielded the 1,4-benzodiazepinone 3-(2-acetamidophenyl)-1,5-dihydro-1,4-benzodiazepin-2one whereas its isomer 2(2-acetamidophenyl)-4,5-dihydro-1,4-benzodiazepin-3-one was obtained from 2-(2-acetylaminophenyl)-N-(2-aminobenzyl)-2-oxoacetamide in acetic acid at room temperature. The previously unknown linear isomer of indolo[3,2-c]quinolin-6-one, i.e. indolo[2,3-blquinolin-11-one, has been prepared by thermal (260degreesC) cyclization of methyl 2-phenylamino indole-3-carboxylate, which in turn was prepared in two steps from methyl indole-3-carboxyl ate. (C) 2003 Elsevier Science Ltd. All rights reserved.
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| 2. |
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| 3. |
- Ek, Fredrik, et al.
(författare)
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Synthesis of Fused Tertazole- and Imidazole Derivatives via Iodocyclization.
- 2003
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Ingår i: Tetrahedron. - 0040-4020. ; 59:35, s. 6759-6769
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Tidskriftsartikel (refereegranskat)abstract
- The possibility to prepare fused tetrazole- and imidazole derivatives by iodocyclization in moderate to excellent yields is demonstrated. In some examples the cyclizations were not following Baldwin's rules entirely, i.e. exo-selectivity. Nucleophilic substitution of the formed iodides gave different results depending on the hardness of the nucleophile. Thus, elimination of the iodide could be a problem but a substitution reaction with ethyl potassium xanthate and a radical reaction using acrylonitrile were tolerated. In addition, we showed that it is possible to selectively use three iodo substituents individually in one of the fused imidazole derivatives.
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| 4. |
- Hedenström, Erik, et al.
(författare)
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Sex Pheromone of pine sawflies. Chiral syntheses of some active minor components isolated from neodiprion sertifer and of some chiral analogues of diprionyl acetate.
- 1992
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Ingår i: Tetrahedron. - 0040-4020. ; 48:15, s. 3139-3146
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Tidskriftsartikel (refereegranskat)abstract
- The chiral syntheses of some analogues, 2 - 7, of 3,7-dimethyl-2-pentadecanol, 1 (diprionol), and of the corresponding acetates are described. The acetate of 1 is the main attractant in the sex pheromone of the Neodiprion genus (Diprionidae). Compounds 2 /2- 4 were identified as minor components isolated from females of Neodiprion sertifer. Synthetic intermediates were prepared either from chiral starting materials, via asymmetric syntheses, or by baker's yeast reductions.
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| 5. |
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| 6. |
- Kahnberg, Pia, et al.
(författare)
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Alternative routes to pterulone
- 2002
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Ingår i: Tetrahedron. - 0040-4020. ; 58:26, s. 5203-5208
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Tidskriftsartikel (refereegranskat)abstract
- Two new synthetic routes to pterulone, a fungal metabolite possessing potent antifungal activity as an inhibitor of NADH/ubiquinone oxidoreductase, are reported. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 7. |
- Leclercq, Sabine, et al.
(författare)
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Furanocembranoid Diterpenes as Defensive Compounds in the Dufour Gland of the Ant Crematogaster brevispinosa rochai
- 2000
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Ingår i: Tetrahedron. - 0040-4020. ; 56:14, s. 2037-2042
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Tidskriftsartikel (refereegranskat)abstract
- Two new furanocembranoid diterpenes, crematofuran [(1R∗,11R∗,12R∗)-6,19:11,12-bisepoxycembra-3,6,8(19),15-tetraene] (1) and isocrematofuran [(1R∗,3S∗,4S∗)-3,4:6,19-bisepoxycembra-6,8(19),11,15-tetraene] (2), have been isolated from the Dufour gland secretion of the Brazilian ant Crematogaster brevispinosa rochai. Their structures, including the relative configuration, have been determined by a combination of NMR and molecular mechanics methods. The toxicity of 1 towards other ants is on the same level as that of nicotine. This is the first report of cembranoid diterpenes as defensive compounds in an ant.
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| 8. |
- Maricic, Suzana, et al.
(författare)
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Synthesis and conformational studies of a Leu-enkephalin amide analogue containing a ferrocene substructure
- 2002
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Ingår i: Tetrahedron. - 0040-4020. ; 58:15, s. 3085-3093
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Tidskriftsartikel (refereegranskat)abstract
- Solution phase synthesis of a constrained Leu(5)-enkephalin amide analogue 10 is reported, in which the cyclic ferrocenyl containing subunit 7 was introduced as a mimetic of the tetrapeptide Tyr-Gly-Gly-Phe unit. Temperature dependence of the chemical shift of the amide protons of 10 indicated a hydrogen bond between the same amino acid residues as observed for the natural Leu-enkepalin in the single-bend conformation. The rotational barrier (DeltaG(c)(not equal)=16.8 kcal/mol) of the C-terminal amide group, which was determined by DNMR spectroscopy, and NOESY experiments indicated that the two termini were more distant as compared to the single-bend conformation of natural Leu-enkephalin amide. (C) 2002 Elsevier Science Ltd. All rights reserved.
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| 9. |
- Olsson, Roger, et al.
(författare)
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Endocyclic cleavage of glycosides. VI. Substituent effects of the alkylative endocyclic cleavage of glycosides
- 1998
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Ingår i: Tetrahedron. - 0040-4020. ; 54:15, s. 3935-3954
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Tidskriftsartikel (refereegranskat)abstract
- A number of pentopyranoside derivatives were treated with Me 3 Al in order to investigate the influence of structural parameters on the methyl group transfer in the endocyclic alkylative cleavage reaction of these substrates. A cyclic CH ··· O hydrogen bonded model is suggested as an intermediate, which is used to explain the stereoselectivities for different substrates. In several, cases the diastereoselectivities were better than 9:1.
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| 10. |
- Rasser, F, et al.
(författare)
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Terpenoids from Bovista sp 96042
- 2002
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Ingår i: Tetrahedron. - 0040-4020. ; 58:39, s. 7785-7789
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Tidskriftsartikel (refereegranskat)abstract
- The novel cytotoxic hexacyclic illudane-illudalane bis-sesquiterpene bovistol (la) was obtained from the basidiomycete Bovista sp. 96042, together with several new sesquiterpenes. la is formed in the fungus by a heteroatom Diels-Alder dimerisation of psathyrellon B (2). (C) 2002 Elsevier Science Ltd. All rights reserved.
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