摘要:

AbstractA new method for the synthesis of naphtho[2,3‐b]pyrandiones from sulfonyllactones and 1‐nitroglycals is presented. Thus, the sulfonyllactone6reacted with the 1‐nitroglycal7in the presence of LDA at room temperature to give the naphthopyrandione9in high yields (Scheme 1). Reaction at a lower temperature led to the (intermediate)Michael‐addition products8. The sulfonyllactone4and the 1‐nitroglycal5were prepared for the synthesis of the naphthopyrandione18(Scheme 2). The base‐promoted condensation of4and5gave17, which was deprotected to give18, the enantiomer of the fungal metabolite (+)‐

ISSN:0018-019X    

DOI:10.1002/hlca.19890720802

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe synthesis of 36 [Fe(CO)2L1(η4‐diene)], three [Fe(CO)2L1(η4‐encne)], and five [Ru(CO)2L1(η4‐diene)] complexes (L1= Ph3P, Et3P, (EtO)3P, (MeO)3p, C6H11NC) by thermal, selective CO ligand displacement in the corresponding tricarbonyl precursor complexes is described. In a second step, photochemical CO displacement by another phosphorus ligand L2leads to a new type of η4‐diene complexes with a centre of chirality at the metal atom (Fe, Ru). 23 Fe and three Ru complexes of this type have been prepared and characterized. In the case of complexes with unsymmetrical dienes, racemic diastereoisomers are formed which can be separated by chromatographic methods. The molecular structures of [Fe(CO)(Ph3P)((MeO)3P)(buta‐1,3‐diene)] (52), [Fe(CO)(Ph3P)((MeO)3P)(isoprene)] (58) and [Fe(CO)(Et3P)(EtO)3P(hexa‐2,4‐dienal)] (62a) were determined by X‐ray diffraction. All complexes were investigated by13C‐,31P‐ and, in part,1H‐NMR spectroscopy. At low temperatures, conformational isomers (rotamers) can be differentiated which probably arise from ψ rotation at

ISSN:0018-019X    

DOI:10.1002/hlca.19890720803

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractReaction of (η3‐allyl)(cyclopentadienyl)zirconium(4+) chloride with (2,3‐dimethylbutadiene)magnesium or (2‐phenylbutadiene)magnesium gave the (η3‐allyl)(η4‐conjugated diene)(cyclopcntadienyl)zirconium complexes3cand3d, respectively. The analogous reaction between (η/3‐allyl)(cyclopentadienyl)hafnium(4+) chloride with (buta‐diene)magnesium afforded (η3‐allyl)(η4‐butadiene)(η5‐cyclopentadienyl)hafnium3e. Photolysis of the complexes3produced their stereoisomers4. The open‐chain π ligands in3open themselves towards the apical Cp ligand, in4they both are turned around by 180°. TheGibbsactivation energy of the4→3rearrangement of the Hf complex does not deviate significantly from those of the Zr‐containing systems (4c→3e: ΔG≠rearr. (−10°) = 81.3 ± 1.3 kJ/mol;4d→3d: ΔG≠(‐10°) = 85.7 ± 1.3 kJ/mol;4e→3e: ΔG≠(‐5°) = 84.4 ± 1.3 kJ/mol). A modified ex‐tended‐Hückeltheory (MEHT) was used in order to simulate the thermally induced rearrangement of the diene ligand in3/4. The calculations indicate that there should be a combinational interconversion of both the diene and allyl ligand. A diene inversion becomes energetically favoured, if a simultanous allyl rotation occurs. The transition state9liesca.90 kJ/mol above the optimized geometry of4aand 115kJ/mol above3a. Orbital considerations show that a spatially different ‘valence’ orbital of the [Zr(allyl)Cp] fragment6in comparison with [ZrCp2]7causes the conformational

ISSN:0018-019X    

DOI:10.1002/hlca.19890720804

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractSynthesis of deaminocolchinyl methyl ether9was achieved from tetramethoxy‐substituted biphenyl‐2‐carb‐aldehyde12viatricyclic ketone20and 5,6‐didehydro congener11. Compound9was identical in every respect with material prepared from colchicinevia6,7‐didehydro congener10. Measuring inhibition of tubulin polymerizationin vitroshowed compounds4,5, and9–11of the alloseries of colchicinoids to be particularly pote

ISSN:0018-019X    

DOI:10.1002/hlca.19890720805

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

Substituent Effects on NMR Spectra of Pentafulvenes.13C,13C‐NMR Coupling Constants (1J(C, C))1H‐ and13C‐NMR spectra of 6‐monosubstituted pentafulvenes1–8have been analysed, and1J(C, C) coupling constants have been determined from ID‐inadequate spectra of13C satellites. It turns out that13C,13C coupling constants of the ring C‐atoms, and especiallyJ(1,2)/J(3,4) andJ(2,3), reflect the extent of π delocalisation in the fulvene ring. With increasing electron‐donating capacity of the substituent R,J(1,2)/J(3,4) values are decreasing, whileJ(2,3) (andJ(1,5)/J(4,5) as well) are increasing, and linear correlations ofHammettsubstituent constants σ+and1J(C,C) va

ISSN:0018-019X    

DOI:10.1002/hlca.19890720806

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe temperature and concentration dependence of the previously reported formation of oligolides from (R)‐ or (S)‐3‐hydroxybutanoic acid underYamaguchi'smacrolactonization conditions (2,4,6‐trichlorobenzoyl chloride/base) was studied. While the content of hexolide2in the product mixture is almost invariablyca.35%, the amounts of pentolide1and of the larger rings strongly depend upon the temperature employed (Fig.1). Cyclic oligomers (5,6) are also obtained from 3‐hydroxypentanoic acid. Enantiomerically pure β‐butyrolactone can be used for the preparation of pento‐, hexo‐, and heptolide underShanzer'smacrolactonization conditions (tetra‐oxadistannacyclodecane ‘template’). The X‐ray crystal structures of the pentolide1and of two modifications (space groupsC2 andP21) of the hexolide2were determined (Figs. 2–6andTables 1 and 5). No close contacts between substituent atoms and atoms in the rings or between ring atoms are observed in these structures. The hexolideC 2modification is ‘just a large ring’, while the crystals of theP21modification contain folded rings the backbones of which resemble the seam of a tennis ball. A comparison of the torsion angles in the folded hexolide ring of theP21modification with those in the helical poly‐(R)‐3‐hydroxybutanoate (PHB) suggests (Table 2) that the same interactions might be responsible for folding in the first and helix formation in the second case. Molecular modeling with force‐field energy minimization of the tetrolide from four homochiral β‐hydroxybutanoic acid units was undertaken, in order to find possible reasons for the fact that we failed to detect the tetrolide in the reaction mixtures. The calculated conformational energies (per monomer) for some of the tetrolide models (Figs. 7–9andTables 3 and 4) are not significantly higher than for the pentolide and hexolide crystal structures. We conclude that thermodynamic instability is an unlikely reason for the lack of tetrolide isolation. This result and failure to observe equilibration of pentolide1to a mixture of oligomers under the reaction conditions suggest that product

ISSN:0018-019X    

DOI:10.1002/hlca.19890720807

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA new synthetic approach towards the indole ring system is described. When dimethyl 1‐methyl‐2‐oxa‐1‐aza‐spiro[4.5]dec‐3‐ene‐3,4‐dicarboxylate (6) was refluxed in toluene, the previously known dimethyl 4,5,6,7‐tetra‐hydro‐1‐methyl‐1H‐indole‐2,3‐dicarboxylate (7) was obtained in 71% yield,viaa 2,3‐dihydroisoxazole‐pyrrole rearrangement. After treatment withDDQ, the tetrahydro analogue7was converted to the corresponding dimethyl 1

ISSN:0018-019X    

DOI:10.1002/hlca.19890720808

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractStarting from dibenzo[a,c]cyclooctene (4) and 4‐methyl‐3H‐1,2,4‐triazol‐3,5(4H)‐dione (MTAD), the strained skeleton of the title azo compound1is assembled in a tandem photo‐Diels‐Alderaddition/di‐π‐methane rearrangement sequence. The synthesis is completed by a stepwise hydrolytic oxidation of the ensuing triazolidine‐dione2with nickel peroxide. Thermolysis of1in benzene solution is shown to be governed by an initial 1,3‐dipolar cycloreversion which leads,viaan intermediate diazo compound11, to cyclobuta[1]phenanthrene8and two further carbene‐derived C16H12products. Photolysis of1at 350 nm leads in modest yield (12%),viaa diazenyl diradical, to an unstable bridged bicyclobutane10(dibenzooctavalene).MNDOcalculations suggest the latter to have a rapidly inverting, twis

ISSN:0018-019X    

DOI:10.1002/hlca.19890720809

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractA series of new 2′–5′ oligonucleotides carrying the 9‐(3′‐azido‐3′deoxy‐β‐D‐xylofuranosyl)adenine moiety as a building block has been synthesizedviathe phosphotriester method. The use of the 2‐(4‐nitrophenyl)ethyl (npe) and 2‐(4‐nitrophenyl)ethoxycarbonyl (npeoc) blocking groups for phosphate, amino, and hydroxy protection guaranteed straightforward syntheses in high yields and easy deblocking lo form the 2′–5′ trimers21,22, and25and the tetramer23. Catalytic reduction of the azido groups in [9‐(3′‐azido‐3′‐deoxy‐β‐D‐xylofuranosyl)adenine]2′‐yl‐[2′‐(Op‐ammonio)→ 5′]‐[9‐(3′‐azido‐3′‐deoxy‐β‐D‐xylofuranosyl)adenin]‐2′‐yl‐[2′‐(Op‐ammonio)→ 5′]‐9‐(3′‐azido‐3′‐deoxy‐β‐D‐xylofuranosyl)adenine (21) led to the corresponding 9‐(3′‐amino‐3′‐deoxy

ISSN:0018-019X    

DOI:10.1002/hlca.19890720810

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe cytotoxically and antivirally active compounds bvUd(1), flUd(4), acyclovir (7), and Aa(12) have chemically been combined with the appropriately protected (2′–5′)diadenylate20by the phosphotriester approach to give the 2′–5′ oligonucleotide trimers21–24. The deprotection of the various blocking groups by chemical means afforded the 2′–5′ trimers25–28, which can be regarded as new type of a potential prodrug form delivering nucleotides to the targets inside cells. In an analogous series of reactions, 9‐(3′‐azido‐3′‐deoxy‐β‐D‐xylofuranosyl)adenine was coupled with7to the 2′–5′ trimer31. The antiviral screening of the oligonucleotides25–27and31showed biological activities closely related to the parent nucleosides, possibly indicating thei

ISSN:0018-019X    

DOI:10.1002/hlca.19890720811

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY