摘要:

AbstractIntramolecular [Pd2(dba)3]/tri(2‐furyl)phosphine‐catalysed (dba = dibenzylideneacetone, PhCHCHCOCHCHPh) cyclisations of olefinic propargylic carbonatesIprovided alk‐1‐enyl‐(3‐aza)bicyclo[3.1.0]‐hexanesVIIIin good yields. A palladium cascade sequenceI→II→III→IV→VII→VIIIis proposed. Furthermore, chiral propargylic carbonates such as23,24and25allowed diastereoselective formation of bicyclo[3.1.0]hexanes29,30and31, respectively. The first diastereoselective synthesis of the monoterpene, (−)‐α‐thujone40illus

ISSN:0018-019X    

DOI:10.1002/hlca.19970800302

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe synthesis of a novel tris(bidentate ligand)ruthenium(II) complex7and its efficient tethering to the 5′‐end of Oligonucleotides is described. The resulting Δ‐ and Δ‐isomeric ruthenium(II)‐labelled Oligonucleotides10a‐‐cand11a‐‐dwere separated either by reversed‐phase HPLC or by polyacrylamide gel electrophoresis. The diastereoisomerically pure isomers were fully characterized by UV/VIS and CD spectroscopy, mass spectrometry, and enzymatic digestion with base analysis. We also investigated the thermal denaturation of the hybr

ISSN:0018-019X    

DOI:10.1002/hlca.19970800303

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe synthesis of a series of bisubstrate inhibitors of the epidermal growth factor receptor protein kinase (EGF‐R PTK) consisting of small pep tides linked covalently to adenosineviaappropriate triphosphate substitutes is described. Boc‐Glu(OtBu)‐Tyr‐Leu‐OBzl (5) and Ac‐Glu(OtBu)‐Tyr‐Leu‐Arg(Pmc)‐NH2(8; Pmc = 2,2,5,7,8‐pentamethylchroman‐6‐sulfonyl) were prepared by standard peptide chemistry, (Scheme 1), then modified at the OH group of tyrosine either with adipic anhydride or with 4‐(chlorosulfonyl)benzoic acid, 4‐(chlorosulfonyl)‐2‐hydroxybenzoic acid, or benzene‐1,4‐disulfonyldichloride (Scheme 2), and finally coupled with the 5′‐OH group of 2′,3′‐O‐isopropylideneadenosine (Scheme 3). In addition,N6‐[(benzyloxy)carbonyl]‐2′,3′‐O‐isopropylidene‐adenosine 5′‐(hydrogenhexanedioate) (26), an ATP substitute, was coupled with the morpholide of5(Scheme 4). Removal of the protecting groups gave the bisubstrate analogs23, 24, and28.The compounds synthesized were tested as inhibitors of the EGF‐R PTK. The most active bisubstrate‐type inhibitor was24, composed of the tripeptide sequence H‐Glu‐Tyr‐Leu‐OBzl, the 2

ISSN:0018-019X    

DOI:10.1002/hlca.19970800304

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractAlkylation of 3‐oxo‐1,2‐thiazetidine 1,1‐dioxide 2 yields theN‐alkylated 3‐oxo‐β‐sultams3a‐i. Solvolysis with NaOH or NH3selectively opens the NS bond forming the sulfonate carboxamides4and the sulfonamidocarboxamides7, respectively. Furthermore, the hitherto unknown compounds of type5are prepared, representing a strained four‐membered ring with a diacylated, sulfonated N‐atom. Depending upon the reaction conditions,3b‐dand3gare rearranged by base‐catalyzed reactions into the substituted 4‐oxothiazolidine 1,1‐dioxides9or10.Structures are elucidated by spectroscopic methods, established by crystal‐structure analyses, and a possible way of formation is proposed. Furthermore, some side reaction

ISSN:0018-019X    

DOI:10.1002/hlca.19970800305

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe structure of rogioldiol A ((−)‐1), isolated from the red seaweedLaurencia microcladia, was determined. Employing the exciton‐coupling technique for rogioldiol Ap‐bromobenzoate (2), the absolute configuration at C(9) of (−)‐1was assigned, and, together with extensive NMR experiments, the absolute configuration at C(10) and preferred conformations of (−)‐1were determined. The absolute configuration of the hetero‐substituted cyclohexane ring was deduced in analogy from the X‐ray structure of4, a derivative of the aldehyde3, which was isolated from the same seaweed and is believed to be a degradati

ISSN:0018-019X    

DOI:10.1002/hlca.19970800306

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractSyntheses of cyclosporine analogues are reported wherein the peptide couplings were achieved in solid phase. TheWangresin was used as the solid support, and the peptide couplings commenced with the residue 11 of the cyclosporine skeleton. The couplings proceeded in a stepwide manner up to the residue MeBmt1, using symmetric anhydrides. The peptides were then cleaved off the resin, and the cyclization was achieved in solution usingCastro's reagent. The solid‐phase synthesis described herein offers a very efficient method for the rapid synthesis of structurally diverse cyclosporine analogues in small quantities. The biological activities of the synthetic cyclosporine analogues were evaluated in twoin vitroassays, including the IL‐2 reporter gene assay and the cyclophilin binding assay. The structure‐activity relationship is disc

ISSN:0018-019X    

DOI:10.1002/hlca.19970800307

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

Synthesis of (3‐Aminopropyl)arylsilanes, Including One or Two Heterocyclic Patterns, Potential FungicidesFlusilazole is an effective silylated fungicide used on a large scale for plant protection. We synthesized several flusilazole analogs and also copied the tebuconazole design, an other very efficient fungicide, which has four atoms between the aromatic group and the heterocyclic moiety. In contrast to flusilazole, we obtained dissymetric structures around the Si‐atom by using successively two differentGrignardreagents. In another way, the 1H‐1,2,4‐triazole moiety was exchanged in several cases by other N‐heterocycles such as 1H‐imidazole, piperidine, and 2,6‐dimethylmorpholine, already present in other fungicidal compounds. Finally, several compounds having two N‐heterocycles of the same or different natur

ISSN:0018-019X    

DOI:10.1002/hlca.19970800308

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractThe photoreduction of triplet benzophenone by 14 tertiary amines was investigated. The ketyl radical yields do not correlate with the quenching rate constants, nor with the electron donor propensity of the amines. Individual structural features of the amines seem to determine the photoreduction yields.

ISSN:0018-019X    

DOI:10.1002/hlca.19970800309

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractNew chromenes annulated with different six‐membered azaheterocycles were prepared,i.e., the 3H‐pyra‐no[3,2‐f]quinolines9/10and14, the 8H‐pyrano[2,3‐h]isoquinoline11, the 8H‐pyrano[3,2‐f]quinazolme12, the 8‐H‐pyrano[3,2‐f]quinoxaline13, and the 2H‐pyrano[2,3‐f]isoquinoline15.The synthesis was achieved using conveniently substituted α,β‐unsaturated aldehydes and organotitanium intermediates arising from azaheterocyclic phenols. Their photochromic behaviour (photocolouration yield, UV/VIS spectrum of photomerocyanines, rate constant of thermal bleaching) were studied besides those of corresponding naphthopyrans. The heterocycle effect and the role of substituents in the pyran moiety were investigated quantitatively through the study of the photochromic properties and the solvent effects. Diaryl‐substituted azino‐fused chromenes, especially isoquinoline derivatives, exhibit increased colourabilities and bathochromically shifted spectra for photomerocyanines which open up new prospe

ISSN:0018-019X    

DOI:10.1002/hlca.19970800310

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY

摘要:

AbstractA comprehensive study of the alkaline hydrolysis of the β‐lactam ring of azetidin‐2‐one was carried out usingab initiomolecular‐orbital calculations at the RHF/6‐31 + G* level. The influence of the solvent on this reaction was investigated by using the reaction field method (SCRF); the solvent was found to suppress the interference of some gas‐phase reactions and allow the presence of a transition state to be detected as the nucleophile approaches the β‐lactam ring. The transition state corresponds to a structure where the OH−group lies at a distance of 1.927 Å from the CO group of the β‐lactam ring and exhibits a potential b

ISSN:0018-019X    

DOI:10.1002/hlca.19970800311

出版商:WILEY‐VCH Verlag GmbH    

年代:1997

数据来源: WILEY