摘要:

AbstractThe optically active (4S,8S)‐4, 8‐bis(hydroxymethyl)‐1,5,7‐triazabicyclo[4.4.0]dec‐5‐ene ((S,S)‐1) has been synthesized in nine steps fromL‐asparagine with a total yield of 5.1%. Similarly, the enantiomer (R,R)‐1has been prepared fromD‐asparagine. (S,S)‐ and (S,S)‐1are representative examples of rigid and functionalized bicyclic guanidine systems and constitute useful intermediates in the construction of chiral selective a

ISSN:0018-019X    

DOI:10.1002/hlca.19880710402

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractDilithium naphthalene (2) and its TMEDA complex3have been prepared, and their1H‐and13C‐NMR spectra were analyzed in terms of chemical shifts and coupling constants. From its Q value,2is characterized as delcoalized [4n] π system and the1H ‐ as well as the6Li‐NMR shifts classify the ion as strongly paratropic. For the quarternary C‐atoms, adown‐fieldshift of 30.4 ppm is observed. The conclusions drawn from the NMR parameters are compared with the results of MNDO calculations for naphthalene and biphenylene an

ISSN:0018-019X    

DOI:10.1002/hlca.19880710403

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe preparation of complexes {AgX(1c)} (X  Cl, Br, I, NO3and ClO4; 1c = 2,11‐bis(diethylphosphinomethyl)benzo[c]phenanthrene) is reported. The31P‐NMR spectra of the above complexes were recorded and the1J(107Ag,31P) values are compared with the corresponding data for related complexes. The X‐ray crystal structure of [Ag(1c)](ClO4) was determined. There are two crystallographically independent molecules in the unit cell each containing two‐coordinate silver, the O‐atoms of the perchlorate anions being outside bonding range from the central atom. The two molecules, however, show different bonding parameters: Thus for ‘molecule 1’ P(1)Ag(1)P(2) = 167.6(1)°, Ag(1)P(1) = 2.389(3) and Ag(1)P(2) = 2.393(3) Å, while for ‘molecule 2’ P(3)Ag(2)P(4) = 164.8(1)°, Ag(2)P(3) = 2.377(3), and Ag(2)P(4) = 2.378(3) Å. These differences are probably due t

ISSN:0018-019X    

DOI:10.1002/hlca.19880710404

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe photosensitized oxygenation of 5‐aryl‐2,4‐diaminopyrimidines1in protic solvent led to the formation of the new 4‐amino‐1,3‐5‐triazin‐2‐yl ketones2in high yields. The structures of2were elucidated by spectroscopical means, especially by13C‐NMR and UV data. Photooxygenation of 2,4‐diamino‐5‐(p‐chlorophenyl)‐6‐ethylpyrimidine1aunder reductive conditions,e.g.In the presence of excess NaBH4, gave 2‐amino‐5‐(p‐chlorophenyl)‐t‐6‐ethyl‐5,6‐dihydro‐r‐5‐hydroxy‐4(3H)‐pyrimidinone (4a), the structure of which was determined by X‐ray analysis. In the proposed mechanisms for both types of reactions, the dipolar ion5is assumed to be a common intermediate. For the new efficient synthesis of 1,3,5‐triazines from 2,4

ISSN:0018-019X    

DOI:10.1002/hlca.19880710405

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe synthesis and antifungal activity of a novel series of 3‐aryl‐5‐[(aryloxy)alkyl]‐3‐[(1H‐imidazol‐1‐yl)‐methyl]‐2‐methylisoxazolidines and related compounds, are discussed. The synthesis of the title compounds was accomplishedviaa 1,3‐dipolar cycloaddition of α‐substituted ketonitrones with l‐alkenyl phenyl ethers (Scheme 2 and 3). The compounds were evaluated forin vitroantifungal activity in solid agar cultures against a broad variety of yeast and systemic mycoses and dermatophytes. While antifungal activity was evident throughout the series, in general, derivatives having halogen atom(s) in either or both aryl rings demonstrated the highest potency, especially againstTrichophyton rubrumandCandida albicans. The dichloro analog20(PR 967‐248) was found to possess the most useful activity. Its minimum inhibitory concentration (MIC) values ranged between 0.2 and 2.0 μg/ml, as compared to 0.2–20.0 μg/ml for

ISSN:0018-019X    

DOI:10.1002/hlca.19880710406

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe temperature dependence of the emission lifetime of the series of complexes Ru(bpy)n(4,4′‐dpb) 2+3−(bpy = 2,2′bipyridine, 4,4′‐dpb = 4,4′‐diphenyl‐2,2′‐bipyridine) has been studied in propionitrile/butyronitrile (4:5v/v) solutions in the range 90–293 K. The obtained photophysical parameters show that the energy separation between the metal‐to‐ligand charge tranfer (3MLCT) emitting level and the photoreactive metal‐centered (3MC) level changes across the series (ΔE= 3960, 4100, 4300, and 4700 cm−1for Ru(bpy) 2+3), Ru(bpy)2(4,4′‐dpb)2+, Ru(bpy)(4,4′‐dpb) 2+2, and Ru(4,4′‐dpb) 2+3, respectively, whereΔEis the energy separation between the minimum of the3MLCT potential curve and3MLCT –3MC crossing point. Comparison between spectral and electrochemical data indicated that the changes inΔEare due to stabilization of the MLCT levels in complexes containing 4,4′‐dpb with respect to Ru(bpy)2+3. The photochemical data for the same complexes (as I−salts) have been obtained in CH2Cl2in the presence of 0.01MCl−upon irradiation at 462 nm. The complexes containing 4,4′‐dpb are more photostable than Ru(bpy) 2+3. Comparison between the data for thermal population of the3MC photoreactive state and those for photochemistry indicated that the overall photochemical process is governed by (i) a thermal redistribution between the emitting and photoreactive excited states, and (ii) m

ISSN:0018-019X    

DOI:10.1002/hlca.19880710407

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractOlefins with captodative substitution are reactive dienophiles inDiels‐Alderreactions with normal and inverse electron demand. This is shown for reactions of 2‐(tert‐butylthio)acrylonitrile (1) with various dienes and heterodienes,e.g.1,3‐cyclohexadiene, hexachloro‐1, 3‐cyclopentadiene, acrolein, methacrolein, and methyl vinyl ketone (Schemes 2and3). In case of the hetrodienes, 3,4‐dihydro‐2H‐pyrans are formed beside small amounts of tetrahydrothiophenes; however, with methyl vinyl ketone, both reaction pathways are equally followed. The high reactivity of captodative olefins inDiels‐Alderreactions are rationalized on the basis ofSustmann's FMO model under consideration of Viehe's concept of captodative subs

ISSN:0018-019X    

DOI:10.1002/hlca.19880710408

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe stability constants for anion binding by the acyclic hexaamine1, its macrocyclic analogue2, and the bicyclic compound3in their protonated forms are reported. Compound3forms stable and selective complexes with halide ions, the stability sequence being I−>Br−>Cl−. Compound2forms more stable complexes with sulfate, oxalate, and malonate dianions than its acyclic analogue1and shows a better selectivity pattern. Compound3forms stronger complexes with oxalate2−than2and shows a remarkably high binding selectivity between oxalate2−and malonate2−. The comparison of the ability of1–3to complex anions demonstrates the macrocyclic and macrobicyclic effects on anion binding stability an

ISSN:0018-019X    

DOI:10.1002/hlca.19880710409

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe synthesis of 6‐amino‐1‐(2′,3′‐dideoxy‐β‐D‐glycero‐pentofuranosyl)‐1H‐pyrazolo[3,4‐d]pyrimidin‐4(5H)‐one ( =8‐aza‐7‐deaza‐2′,3′‐dideoxyguanosine;1) from its 2′‐deoxyribofuranoside5aby a five‐step deoxygenation route is described. The precursor of5a, 3a, was prepared by solid‐liquid phase‐transfer glyscosylation which gave higher yields (57%) than the liquid‐liquid method. Ammonoloysis of3bfurnished the diamino nucleoside3c. Compound1was less acid sensitive

ISSN:0018-019X    

DOI:10.1002/hlca.19880710410

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY

摘要:

AbstractThe reactivity of 1,3‐propanesultone with adenine, adenosine, and NAD+was studied in order to prepareN6‐(3‐sulfonatopropyl)‐NAD+(3b), a new NAD+derivative substituted at the purine moiety with sunstantial coanzyme activity for several dehydrogenases. The regiochemistry of the alkylation at the purione nucleus was investigated by UV,1H‐NMR, and FAB‐MS proved to be a powerful tool for determining the molecular weight of these polar and poorly volatile compounds. In addition, regular framgmentation of3band other NAD+derivatives w

ISSN:0018-019X    

DOI:10.1002/hlca.19880710411

出版商:WILEY‐VCH Verlag GmbH    

年代:1988

数据来源: WILEY