摘要:

AbstractEvidence is presented for the first time that ‘naked’ Fe+ions, complexed to the NH2group of primary amines, are capable of intramolecularly activating CC bonds in a highly specific mode without preceding CH act

ISSN:0018-019X    

DOI:10.1002/hlca.19890720402

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

Novel Bis(dimethinemerocyanine) Dyes with Isolated Chromophores in the Molecule Containing the Sulfobutyl Group and their Aggregation Tendency in Aqueous SolutionThe bis(dimethinemerocyanine) dyes7a–cwith Chromophores separated by a polymethylene chain as ‘isolator’ are synthesized in good yield. Their aggregation tendency in organic solvents, organic solvents/H2O mixtures, and in H2O is investigated. In organic solvents, the dyes7a–bshow a splitted absorption band, due to interaction of the two Chromophores of the dye. In H2O,7aexhibits an intense absorption band at 496 nm (ϵ = 224 300 1·mol−1·cm−1) with a small width\documentclass{article}\pagestyle{empty}\begin{document}$ (\tilde v_{{\raise0.7ex\hbox{$1$} \!\mathord{\left/ {\vphantom {1 2}}\right.\kern-\nulldelimiterspace} \!\lower0.7ex\hbox{$2$}}} = 1000\;{\rm cm}^{ - 1}) $\end{document}and shoulders at 552 and 580 nm. In presence of starch, this absorption band shifts to 617 nm, probably due to J‐aggregation. The dye7bshows the same spectral behaviour as7a. In contrast,7cexhibits an absorption band without splitting in organic solvents; the interaction of the Chromophores has disappeared. In H2O and in H2O containing starch,7cshows a wide absorption band, due to interaction of the Chromop

ISSN:0018-019X    

DOI:10.1002/hlca.19890720403

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe [Co2(CO)8]‐mediatedretro‐Diels‐Alderreaction of the annelated barrelenes1afforded the 1H‐indol‐2(3H)‐one derivatives3(Scheme 1), while the hydrobarrelene4a, under the same conditions, was converted to the anilide6(Scheme 2);4bremained unaffected. The direct irradiation of1led to the annelated cyclooctatetraenes7(Scheme 3). On irradiation in the presence of excess of [Fe(CO)5],1a,1b, and4agave the tricarbonyliron complexes8,9, and11, respectively (Schemes 3and4); under these conditions,

ISSN:0018-019X    

DOI:10.1002/hlca.19890720404

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe first total enantioselective synthesis of (+)‐(4S, 8R)‐8‐epi‐β‐bisabolol(+)‐1and of (−)‐(4R, 8S)‐4‐epi‐β‐bisabolol ((−))−1) is reported. The key step in the synthesis is the kinetic resolution of (±)−5by means of theSharplessepoxidation yielding (−)‐ and (+}−6, respectively. Reduction of the epoxides with LiAlH4gave the diols (+)‐and(−)−7which were transformed into (+)‐ and (−)−8, respectively,viathe corresponding mesylate. Reaction of these epoxides with theGrignardreagent derived from homoprenylbromide, assisted by Li2CuCl4, finished the synthesis of the target com

ISSN:0018-019X    

DOI:10.1002/hlca.19890720405

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractBeside the known naphthoquinones, dehydro‐α‐lapachone (17) and lapachol (20), four new naphtho[2,3‐b]‐furan‐4,9‐diones,i.e.the 2‐acetyl‐5‐hydroxy. 2‐acetyl‐8‐hydroxy. (−)‐5‐hydroxy‐2‐(1′‐hydroxyethyl), and (±)‐8‐hydroxy‐2‐(1′‐hydroxyethyl) derivatives16, 15, 12, and13, respectively, and the new compound benzo[b]furan‐6‐carboxaldehyde (8) have been isolated from a CHCl3extract of the inner stem bark ofTabebuia avellanedaeLORENTZexGRISEB., together with four known naphthofurandiones, a dihydroisocoumarin derivative, (−)–6‐hydroxymellein, and five benzoic‐acid and three benzaldehyde derivatives which have not been reported previously from this plant. Structure determination of the isomeric 5‐ and 8‐hydroxynaphtho[2,3−b]furan‐4,9‐diones was carried out unambiguously by a comb

ISSN:0018-019X    

DOI:10.1002/hlca.19890720406

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractActivity‐guided fractionation of the MeOH extract of the fruits ofTetrapleura tetrapteraTAUB. (Mimosaceae) afforded4saponins1–4, which exhibited strong molluscicidal properties against the schistosomiasis‐transmitting snailsBiomphalaria glabrata.Chemical, enzymatic, and spectral methods (DCI‐MS,1H‐NMR,13C‐NMR) showed that they wereN‐acetylglycosides of oleanolic acid and of echinocystic acid. Apart from saponin1(aridanin), previously isolated from this plant, glycosides2–4are new naturally occu

ISSN:0018-019X    

DOI:10.1002/hlca.19890720407

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe bimorphinans1(binaltrorphimine),3, and7have been prepared by treatment of the parent morphinan‐6‐ones naltrexone (5), naloxone (4), and dihydrocodeinone (6), respectively, withN‐methylhydrazine sulfate in AcOH at room temperature. Compound3showed opioid antagonist potency and selectivity forKreceptors which were somewhat lower in compariso

ISSN:0018-019X    

DOI:10.1002/hlca.19890720408

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

Synthesis of a Biotinylated Probe with an Extended Cleavable Arm for Angiotensin II Receptors PurificationWe have synthesized a new biotinylated probe for angiotensin II receptors studies: biotinyl‐NH(CH2)2SS(CH2)2CO‐Gly‐ϵ Ahx‐[Ala1, Phe(4N3)8]angiotensin II (5). This molecule can be photoactivated through an arylazido group.1H‐NMR studies suggest that it adopts an extended conformation which should allow a simultaneous recognition of both streptavidin and hormone receptor. It has a good affinity for receptors (Kd= 1 nM) and hence is a promising tool in their detection (autoradiography, gold‐, ferritin‐, enzyme‐, or fluorescent streptavidin derivatives) and separation (cell sorting, affinity chromatography). It can be monoiodinated (°6) at its tyrosine residue without a significant loss of affinity. Its extended cleavable arm allows an easy recovery of the ‘probe‐receptor’ complex from streptavidin. An HPLC monitoring of the synthesis is described, particularly of the segment coupling1 + 2in presence of (benzotriazol‐1‐yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP). This method can be used as well for synthesis of theD‐Phe8deriva

ISSN:0018-019X    

DOI:10.1002/hlca.19890720409

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractEthyl (1R, 2S)‐2‐hydroxycyclopentanecarboxylate and ‐cyclohexanecarboxylate (1aand2a, respectively) obtained in 40 and 70% yield by reduction of 3‐oxocyclopentanecarboxylate and cyclohexanecarboxylate, respectively (Scheme 2), with non‐fermenting yeast, are converted to bicyclic dioxanone derivatives3and4with formaldehyde, isobutyraldehyde, and pivalaldehyde (Scheme 3). The Li‐enolates of these dioxanones are alkylated (→5a–5i,5j,6a–6g), hydroxyalkylated (→51, m, 6d, e), acylated (→5k, 6c) and phenylselenenylated (→7–9) with usually high yields and excellent diastereoselectivities (Scheme 3, Tables and 2). All the major isomers formed under kinetic control are shown to havecis‐fused bicyclic structures. Oxidation of the seleno compounds 7–9 leads to α, β‐unsaturated carbonyl derivatives10–13(Scheme 3) of which the products12a–cwith the CC bond in the carbocyclic ring (exocyclic on the dioxanone ring) are most readily isolated (70–80% from the saturated precursors).Michaeladdition of Cu(I)‐containing reagents to12a–cand subsequent alkylations afford dioxanones14a–iand16a–dwithtrans‐fused cyclohoxane ring (Scheme 4). All enolate alkylations are carried out in the presence of the cyclic urea DMPU as a cosolvent. The configuration of the products is established by NMR measurements and chemical correlation. Some of the products are converted to single isomers of monocyclic hydroxycyclopentane (17–19) and cyclohexane derivatives (20–23;Scheme 5). Possible uses of the described reactions for EPC synthesis are outlined. The observed steric course of the reactions is discussed and compared with that of analogou

ISSN:0018-019X    

DOI:10.1002/hlca.19890720410

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY

摘要:

AbstractThe dye‐sensitized photo‐oxygenation of 3‐hydroxyestra‐1,3,5(10), 9(11)‐tetraen‐17‐one (8) gives a complex mixture from which only the 1,4‐endo‐peroxide10can be isolated in low yield. In contrast, the 3‐methoxy derivative9yields the C‐seco‐aldehyde11as a major product, suggesting that 1,2‐dioxetane is a primary photo‐oxygenation intermediate. As the electron‐donating character of the substituent at C(3) decreases in the sequence12(R = PhCO),13(R = Ac), and14(R = Ts), the rate constant in substrate disappearance becomes drastically smaller as compared with8and9, and no photoproducts are detected. The results are rationalized by means of electron

ISSN:0018-019X    

DOI:10.1002/hlca.19890720411

出版商:WILEY‐VCH Verlag GmbH    

年代:1989

数据来源: WILEY