摘要:

AbstractThe world oceans represent a resource of huge dimension, but their microbial diversity is still poorly understood. The chemistry of marine fungi was even a widely neglected part of natural product chemistry until recently. But symbiotic and epibiotic coexistence of fungi with higher forms of life,e.g. with sponges, forming highly specialised communities gave rise to an increasing interest in their secondary metabolism. More than 100 metabolites from marine fungi are known now, many of them showing fascinating structures or remarkable biological activities. This review gives a comprehensive summary of most structures and discusses their origin and properties.

ISSN:0941-1216    

DOI:10.1002/prac.19983400702

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

AbstractThe syntheses and the properties of new sulfurligated liquid crystalline sulfones, containing biphenyl units, as well as the influence of lateral nitro groups on their phase behaviour are described. Differential scanning calorimetry, optical polarizing microscopy and X‐ray diffraction measurements reveal liquid crystalline properties for most of the synthesized bis(4‐alkoxy‐biphenyl‐3‐yl)sulfones (4). The mesomorphic behaviour of these compounds is compared with that of the corresponding nitro compounds6. The bis(4‐alkoxy‐6‐nitrobiphenyl‐3‐yl)sulfones (6) are not mesogenic. The results demonstrate that lateral nitro groups introduced into the biphenyl unit, changing the length‐breadth relation, depress the thermal stability and lead to the loss of the m

ISSN:0941-1216    

DOI:10.1002/prac.19983400703

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

Synthesis and Spectroscopic Properties of Alkylquinoline‐8‐ol Extractants and their Cu(II)‐, Zn(II)‐ and Cd(II)‐ComplexesA series of deprotonizable chelating agentsHLbeing characteristic of 2‐, 5‐ and 7‐alkyl substituted 8‐hydroxyquinolines or 5‐ and 7‐alkyl substituted 8‐hydroxyquinaldines of different alkyl chain length,H1–H5, and their Cu(II)‐, Zn(II)‐ und Cd(II)‐complexes,M(1)2–M(5)2, have been synthesized. Influences of the alkyl groups, including substituent effects on the spectroscopic properties (MS, IR, UV‐VIS,1H und13C NMR) of the free li

ISSN:0941-1216    

DOI:10.1002/prac.19983400704

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

AbstractNitrilimines2are found to react with alkoxycarbonylhydrazines3–5to afford the acyclic adducts6–8. 6cis oxidized upon heating with charcoal in refluxing toluene to the corresponding formazan9c. Compounds8cyclize upon heating with charcoal in refluxing toluene to the corresponding 6‐acetyl‐4‐aryl‐2‐ethoxycarbonyl‐1,2,3,4‐tetrahydro‐s‐tetrazines (10) rather than to the expected corresponding tetrazinones11. NMR study of compounds10showed that these compounds exist in a t

ISSN:0941-1216    

DOI:10.1002/prac.19983400705

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

Abstract2‐Amino‐4,5‐dihydro‐3‐furancarbonitriles (1) react with α‐diazo‐β‐keto esters in the presence of rhodium (II) acetate to give alkyl 2H‐pyran‐2‐carboxylates (2) in good yields. Benzoylation of2with benzoyl chloride provided alkyl 3‐benzoylimino‐2H‐pyran‐2‐carboxylates (4). The formation of2could be explained by a mechanism involving an oxonium ylide derived

ISSN:0941-1216    

DOI:10.1002/prac.19983400706

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

AbstractMolecular threadsI–IIIincorporating 1,3,5‐cycloheptatriene units have been synthesized by three methods. Bridges were designed as ether (9,14,18and22), ester (4and14) and amino functions (25), respectively, The attachment of a second aryl residue at the seven‐membered ring by nucleophilic attack of activated aromatic compounds such as anilines on tropylium salts resulted in the formation of two regioisomers (26and27). The macrocycles28were formed under high dilution conditions in good y

ISSN:0941-1216    

DOI:10.1002/prac.19983400707

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

Abstract2,6‐Dimethoxy‐(4a), 2,6‐bis(dimethylamino)‐(4b), 2,6‐dichloro‐ (4c) and 2,6‐dimethoxycarbonyl‐9,10‐dihydroanthracene (4d) were prepared by conventional methods and used as hydrogen transfer donors to α‐methylstyrene (5) between 290‐350 °C. The mechanism followed second order kinetics and the rate constants were only slightly influenced by the solvent polarity and the type of substituents introduced. The activation parameters are also closely similar in the series with ΔS≠values between −21 and −28 cal/mol K. These results, together with the observation of a large isotope effect (kH/kD= 1.4–2.0 at 310–350 °C), suggest that the mechanism involves a primary kinetic H‐atom‐transfer from the donors to α‐methylstyrene (5) in the rate determining step. The compounds4a–4dconstitute a new probe for investi

ISSN:0941-1216    

DOI:10.1002/prac.19983400708

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

AbstractA variety of 6H‐1,2‐oxazines10could efficiently be prepared by hetero Diels–Alder reaction of α‐nitroso alkenes2with 1‐bromo‐2‐ethoxyethene (8) and consecutive elimination of HBr by DBU. Heterodienes2were generatedin situfrom α‐halogen oximes6. Primary cycloadducts9were isolated in singular cases, however, an attempt to substitute bromide in9eby an azido group gave the desired compound11only as minor component together with elimination product10e. 6H‐1,2‐oxazines10are valuable precursors for addition reactions which open new sy

ISSN:0941-1216    

DOI:10.1002/prac.19983400709

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

AbstractStarting from the benzylidene lactone3of D‐(−)‐quinic acid the cyclohexyl fragment15(C‐28‐C‐34 part) of the immunosuppressant FK506 was synthesized. Key steps include homolytic deoxygenation reactions on compounds4and6as well as a regioselective opening of the benzylidene acetal5. Opening of the lactone7to provide the methyl ester8was followed by methylation of the hydroxy group to give9. Further steps provided the aldehyde12which was elongated to the alkyne15. This sequence provides15in gram

ISSN:0941-1216    

DOI:10.1002/prac.19983400710

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY

摘要:

AbstractThe synthesis of racemic and enantiomerical enriched axial chiral liquid crystalline compounds incorporating a trisubstituted allene unit is described. All compounds16–28display the smectic C‐phase and mostly also a nematic mesophase. All investigated enantiomerically enriched compounds have a ferroelectrically switchable chiral smectic SC*‐

ISSN:0941-1216    

DOI:10.1002/prac.19983400711

出版商:WILEY‐VCH Verlag GmbH    

年代:1998

数据来源: WILEY