摘要:

AbstractA review is given of certain aspects of manganese‐containing enzymes, such as manganese superoxide dismutase, manganese catalase, and the photosynthetic oxygen‐evolving catalyst. A variety of manganese complexes have been synthesized to model either the structure of the active site of these enzymes (structural models), or their function (functional models). Most of the enzymatic reactions can be mimicked by functional models, albeit at much lower reaction rates. Additionally, a number of manganese complexes based on the structural mimics, have been studied as catalysts in oxidation reactions other than the enzymatic ones.Examples of functional models for superoxide dismutase, catalase and the water oxidation catalyst in plants, as well as a number of manganese complexes catalyzing a variety of other oxidation reactions, are also discussed in this rev

ISSN:0165-0513    

DOI:10.1002/recl.19961150902

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe easy accessible building units 5‐O‐(2,3,4,6‐tetra‐O‐benzoyl‐α‐D‐mannopyranosyl)penyl 2‐cyanoethylN,N‐diisopropylphosphoramidite (9) and 2,2‐bis(4,4′‐dimethoxytrityloxymethyl)propyl 2‐cyanoethylN,N‐diisopropylphosphoramidite (12) were used for the sequential elongation of immobilized tetrametric thymidylic acid according to a DNA synthesis protocol. Ammonolysis of the individual immobilized adducts led to the isolatio

ISSN:0165-0513    

DOI:10.1002/recl.19961150903

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractCrystals of 5,17‐bis(acetamido)‐25,26,27,28‐tetrapropoxycalix[4]arene · ethyl‐acetate (1: 1), C44H54N2O6· C4H8O2are triclinic, space groupP‐1,a= 13.319(4),b= 15.519(4),c= 22.386(6) Å, α = 104.73(3), β = 99.02(3), γ = 95.30(3)°,T= 100(5) K, Z = 4. The asymmetric unit contains two calix[4]arene molecules and two ethyl acetate molecules. The two calix[4]arene molecules have different pinched cone conformations. The phenyl rings show small but consistent boat‐like deformations. The fi

ISSN:0165-0513    

DOI:10.1002/recl.19961150904

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractReactions of optically pure 1‐aryl‐2,2‐dimethylpropane‐1,3‐diols with phenylglyoxal give diastereomerically pure cyclic ketals under acid catalyzed conditions. The structure of one of the products, 2‐phenyl‐4‐(2‐chlorophenyl)‐5,5‐dimethyl‐1,3‐dioxane‐2‐carbaldehyde (7), has been determined by X‐ray crystallography; reaction takes place at the keto group and the ald

ISSN:0165-0513    

DOI:10.1002/recl.19961150905

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractIn THF solution, NaBH4in the presence of (S)‐(‐)‐1‐(2‐chlorophenyl)‐2,2‐dimethylpropane‐1,3‐diol together with 2‐chlorobenzoic acid reduced propiophenone to 1‐ phenylpropan‐1‐ol in up to 40% enantiomeric excess (ee). Only 21%eewas obtained without an added acid. (R)‐(‐)‐butane‐1,3‐diol and (R)‐( + )‐1,1′‐binaphthalene‐2,2′‐diol did not form clear solutions with NaBH4in THF and only gave a lowee.Of the organic acid additives investigated, (S)‐(–)‐4‐(2‐chlorophenyl)‐5,5‐dimethyl‐2‐hydroxy‐1,3,2‐dioxaphosphorinane 2‐oxide gave the highestee(46%). However, with AlCl3/NaBH4/(S)‐(–)‐1‐(2‐chlorophenyl)‐2,2‐dimethylpropane‐1,3‐diol in THF the best result was obtained (ee55%).Asymmetric Meerwein‐Ponndorf‐Verley (MPV) reductions of acetophenone by isopropanol in the presence of these chiral diols as auxiliary have also been carried out. For the case of aluminium triisopropoxide, (R)‐(–)‐1‐phenyl‐2,2‐dimethylpropane‐1,3‐diol and acetophenone(1/1/1), aneeof up to 20% for 1‐phenylethanol was obtained whereas with (R)‐(+)‐1,1′‐binaphthalene‐2,2′‐diol aneeof 32% was obtained. Lanthanide triisopropoxides, Ln(OiPr)3, have also been used. Of the various lanthanides (Ln = La, Y, Er, Tb, and Eu) the Er triisopropoxide with chiral (R)‐(–)‐1‐phenyl‐2,2‐dimethyl‐propane‐1,3‐diol gave the best result; 46%eefor 1‐phenylethanol. Lanthanide chloride diisopr

ISSN:0165-0513    

DOI:10.1002/recl.19961150906

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19961150907

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19961150909

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19961150911

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19961150901

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY