摘要:

AbstractLiquid crystalline phthalocyanines with eightn‐alkoxy chains have been synthesized and their mesophase structures determined by X‐ray diffraction. The mesophases appear to be of the Dhotype. Reasons for the preference of ordered columns are discus

ISSN:0165-0513    

DOI:10.1002/recl.19881071102

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractModification of the methyl group in 2‐(methylsulphonyl)ethanol gave alcohols which could be used to introduce amino‐protective groups of the urethane type, which are labile in alkaline media. The cleavage involves β‐elimination.Exchange of the methyl group by a phenyl group bearing a function with a negative inductive effect (NO2or MeSO2) afforded protecting groups with a higher sensitivity to base. The recommended function is a disulphone: 2‐[4‐(methylsulphonyl)phenylsulphonyl]ethanol. The function has a somewhat better stability than the Fmoc group, resists catalytic hydrogenolysis, is highly stable in acidic medium and its elimination product does not polymerize spontaneously. The suggested designation of the new protective gr

ISSN:0165-0513    

DOI:10.1002/recl.19881071103

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe synthesis of [(3‐13C)‐3‐aminopropyl]triethoxysilane (la) from (1‐13C)acrylonitrile (4a) is described. The latter was prepared from potassium (13C)cyanide (13C‐enrichment>99%) and 2‐bromoethanol (7). The spectroscopic properties of the13C‐substituted compounds

ISSN:0165-0513    

DOI:10.1002/recl.19881071104

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe photo‐isomerization of (Z)‐3‐(6′,6′‐dimethyl‐2′‐methylenecyclohexylidene)‐1‐propene [(Z)‐3a] has been studied under conditions of triplet photosensitization, using benzophenone as sensitizer, and direct irradiation with λ 254 nm. Under the former conditions, onlyZ‐Eisomerization is observed leading to a photostationary state with {[Z]/[E]}pss= 1.77 and 1.50 for benzene and chloroform as the respective solvent. Upon direct irradiation, the primary products are (E)‐3a, the tricyclodecene 11a and the bicyclooctene 12a, formed in an initial ratio of 9/2.0/1.0. The two polycyclic isomers 11a and 12a apparently result from the excited singlet state. NOE1N NMR measurements illustrate hat (Z)‐3a is present mai

ISSN:0165-0513    

DOI:10.1002/recl.19881071105

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe synthesis of analogue 14f (Scheme 2) of a fragment of theS. pneumoniaetype 1 C‐substance antigen (Fig. 1, Ia) is presented. The protected disaccharide 5 and trisaccharide 7 (Scheme 1) were prepared by silver trifluoromethanesulfonate‐catalyzed α‐glycosylation of 2c with 4b (54%) and 2d with 6b (59%), respectively. A silver‐silicate‐catalyzed β‐glycosylation of ribitol derivative 9 with trisaccharide bromide 8b gave 10a (55%). The selectively deprotected trisaccharideribitol 10b was coupled with spacer 11 (Scheme 2) using phosphorylating reagent 12 to give the fully protected phosphotriester derivative 14a (98%). The stepwise deprotection of 14a, including conversion of the azide functions into acetamido groups, turned out to be troublesome and afforded 14f

ISSN:0165-0513    

DOI:10.1002/recl.19881071106

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractThe title compounds are prepared either (A) from 1‐(1‐chloroalkyl)benzotriazoles and aldehydes via Wittig reaction or (B) from 1‐[1,1‐bis(trimethylsilyl)alkyl]benzotriazoles by alkylative desilylation by fluoride ion in the presence of a carbonyl compound (in one instance by lithiation of the silyl compound and subsequent reaction with a carbonyl electrophile) via a Peterson olefination. The methods are applicable to both alkyl and aryl ketones and to aldehydes, with method (B) giving the highest

ISSN:0165-0513    

DOI:10.1002/recl.19881071107

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractHeating of starch or other (1→4)‐glucans in a conventional microwave oven yields 1,6‐anhydro‐β‐D‐glucopyranose within a few minutes. Preparation of small amounts of this compound is rapid and easy by

ISSN:0165-0513    

DOI:10.1002/recl.19881071108

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

摘要:

AbstractConformational analysis of a biologically active heparin like oligosaccharide, which contains a glyceric acid‐O‐CH2‐O moiety instead of iduronic acid, was performed by high field (600 MHz)1H‐NMR spectroscopy. Most remarkably, the glyceric acid ‐O‐CH2‐O moiety adopts a linear conformation in which the anomeric effect does not operate. Most likely, this phenomenon should be ascribed to electrostatic repulsions among the charged sulphate and carbo

ISSN:0165-0513    

DOI:10.1002/recl.19881071109

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19881071110

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY

ISSN:0165-0513    

DOI:10.1002/recl.19881071112

出版商:WILEY‐VCH Verlag    

年代:1988

数据来源: WILEY