摘要:

AbstractThe synthesis is described of four pentasaccharides, which are structurally related to the bacterial capsular polysaccharide isolated fromE. coliK5 (010/K5/H40),i.e.the so‐called K5 antigen.These four synthetic compounds comprise:(i) a pentasaccharide that is structurally identical to the K5 antigen (i.e.compound16);(ii,iii) two pentasaccharides containing two and threeO‐sulphated groups respectively on defined positions (i.e.compounds15aand15b);(iv) a pentasaccharide that isO‐sulphated on all hydroxyl groups (i.e.compound17). These four K5‐antigen‐related pentasaccharides were synthesized from the fully protected pentasaccharides13aand13b. The preparation of compounds13a,bwas based on coupling of disaccharide6bwith the disaccharide10aor10bto give tetrasaccharides11a,c, respectively, which in turn were coupled to monosaccharide12. Deblocking of the pentasaccharides13a,band conversion into the pentasaccharides15aand15bwas performed by saponification of the ester functions,O‐sulphation, hydrogenolysis and finally selectiveN‐acetylation. Compound16was obtained from13a,bby saponification of the ester functions, deblocking of the benzyl andN‐protective groups, followed by selectiveN‐acetylation. The persulphated derivative17was obtained from15aby extensiveO‐sulphation. The structure of theK5‐antigen‐related pentamers was confirmed by1H NMR‐ and13C NMR

ISSN:0165-0513    

DOI:10.1002/recl.19891080202

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe synthesis of (1′‐13C)‐, (3‐13C)‐ and (2,4‐13C2)citric acid from simple starting compounds is described. Using the same procedure, any mono‐ or multiply‐labelled citric acid can be prepared.The13C‐labelled citric acids have been characterized by1H NMR,13C NMR and

ISSN:0165-0513    

DOI:10.1002/recl.19891080203

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe structural changes of coordination compounds of polyhydroxy carboxylic acids as a function of the pH are discussed. A general coordination‐ionization scheme, based on literature data and covering some forty cations, is provided. The following trend is observed on going from low to high pH: (i)bidentate coordination of the cation by the α‐hydroxy carboxylic acid moiety, (ii) ionization of the carboxylic acid function, (iii) ionization of the α‐hydroxyl group and (iv) coordination by an ionized‐diol function. For complexes of metal ions, the pH effects are correlated with the acidity of the hydrated cation and explained using an extended electrostatic model. The coordination‐ionization scheme provides an explanation for and allows prediction of both metal‐ion‐catalyzed addition reactions and synergetic effects in sequ

ISSN:0165-0513    

DOI:10.1002/recl.19891080204

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractThe reaction of 1‐oxo‐2‐thioxo‐indaneS‐oxide 1 with 1‐(trimethylsilyl)‐1H‐indene2gaveendo‐2‐oxo‐7‐(trimethylsilyl)‐5,6‐benzo‐2‐thiabicyclo[2.2.1]hept‐5‐ene‐3‐spiro‐2′‐indan‐1′‐one3as the sole product. The crystal and molecular structure of the corresponding sulfone,4, C21H22O3SSi, was established by X‐ray diffraction analysis. Theendostructure of the sulfoxide3was deduced from1H NMR spectra. The formation of the p

ISSN:0165-0513    

DOI:10.1002/recl.19891080205

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

Abstract2‐Benzoyl‐ and 2‐(2‐naphthoyl)pyrrolidines which can be viewed asarylα‐amino ketones, have been prepared from L‐proline via Grignard reactions, bromo‐to‐lithium exchange, or by Friedel‐Crafts acylations. It was impossible to convert the ketone function of thesearylα‐amino ketones into atert‐alcohol group. The BOC‐protected (S)‐2‐acetyl‐l‐pyrrolidine (15), obtained by reaction of BOC‐proline 2‐pyridinethiol ester (2) with LiMe2Cu, could be converted in two steps into the amino alcohol17, which contains atert‐alcohol function. Upon treatment of17with BBr3, followed by air oxidation, mitosene20was obtained in a low yield. The Friedel‐Crafts reaction products23of 1,4‐dimethoxynaphthalene, or 2,5‐dimethoxytoluene and (S)‐l‐(trifluoroacetyl)–2‐pyrrolidinecarbonyl chloride, could be converted in two steps into theisomitosanes25. The isomitosanes25could easily be dehydrated, using acid, to the corresponding mitosenes26. Upon reduction of the isomitosanes25with Na2S,2O4to the correspond

ISSN:0165-0513    

DOI:10.1002/recl.19891080206

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractUsing low‐temperature trapping experiments with 1,1‐diphenyl‐2‐picrylhydrazine monitored by UV/Vis spectroscopy, it is shown that the rate‐determining step in the epoxidation of alkenes by hypochlorite, catalysed by manganese(III) porphyrins, involves the formation of the active oxo‐manganese specie

ISSN:0165-0513    

DOI:10.1002/recl.19891080207

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080208

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

摘要:

AbstractAceanthrene (2) and aceanthrylene (1) are easily prepared in high yield from aceanthrenequinone (3) by means of a double Wolff‐Kishner reductio

ISSN:0165-0513    

DOI:10.1002/recl.19891080209

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080211

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19891080212

出版商:WILEY‐VCH Verlag    

年代:1989

数据来源: WILEY