摘要:

AbstractSolvolytic reactions ofN‐methoxycarbonyl‐D‐ and L‐phenylalaninep‐nitrophenyl ester (D‐2and L‐2) by poly(N‐methacryloyl‐L‐histidine) and poly(N‐methacryloyl‐L‐histidine methyl ester) were carried out. However, no significant difference between the solvolytic rates of the two enantiomeric substrates was observed. To investigate the effect of hydrophobic interaction,N‐acetyl‐,N‐pentanoyl‐ andN‐octanoyl‐L‐histidine were prepared and their effect on the ester solvolyses was studied. The rates were generally enhanced as the alkanoyl group became larger. FurthermoreN‐octanoyl‐L‐histidine showed some degree of stereoselective catalysis. Accordingly, when polymers with increased hydrophobicity were prepared by copolymerizingN‐methacryloyl‐L‐histidine and its methyl ester with dodecyl methacrylate and were subjected to catalyze the solvolyses of optically active esters, the apparent catalytic rate constant for L‐2was observed to be 1,3 times larger than that for the D‐2. The enantio‐selectivity became more pronounced as th

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830901

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe present paper reports on the synthesis of copolymers of (—)‐p‐(3‐menthyl) acrylate (1) with 4‐vinylpyridine (2) by radical polymerization in a large range of composition. Reactivity ratio values of the two comonomers, evaluated by the Kelen‐Tüdös method, have allowed to show that2exhibits a rather high reactivity as compared with1. The average sequence length of the co‐units and their distribution in the macromolecules were evaluated. The chiroptical properties of side chain pyridine chromophores were investigated by circular dichroism measurements and related to composition and distribution of the

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830902

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe di(cyanomethyl) methylsuccinate derivative of cytosine and di(p‐nitrophenyl) methyl‐succinate derivative of hypoxanthine were prepared and polycondensed with a variety of diamines to provide powdery polyamides with molecular weights in the range of 1000–3100. The polyamides are soluble in DMSO and formic acid, but insoluble in ordinary organic sol

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830903

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe template effect of polymers containing the adenine residue,6, bound to a polystyrene backbone via a spacer group, on the polycondensation of active esters of thymine,1, and theophylline,2, with piperazine was studied in pyridine/methylene chloride or DMF. Template polymers accelerated the polycondensation of1with diamines by a factor of 5–20, but the polycondensation of2with piperazine showed no considerable template effec

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830904

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe carbonation reactions of polymeric organolithium compounds with high purity, gaseous carbon dioxide have been investigated in benzene and benzene/tetrahydrofuran (75/25) solutions. The polymers investigated were poly(styryl)lithium, poly(isoprenyl)lithium, and poly(styrene‐b‐isoprenyl)lithium. In Benzene solution the products are a mixture of the carboxylic acid and the ketone (dimer). No tertiary alcohol product (trimer) was observed. In benzene/tetrahydrofuran solution, the quantitative carboxylation of chain ends was obser

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830905

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractPolyesterification products with tetrathiafulvalene units3a–ewere prepared from tetrathiafulvalenedicarbonyl dichloride (1) and various α,ω‐diols (2a–e) containing 2 to 16 methylene groups. The red to brown products3a–ewith melting points between 235°C and 128°C are insoluble in all common organic solvents, except for3ewhich is soluble in hot DMF. Molecular weights determined by vapor pressure osmometry as well as from elemental analysis data have been found to be ≥2000. The structures were proved by IR, MS, and electronic spectra. The electrical conductivities of3a–eare between 4 . 10‐8and 4 · 10‐13Ω‐1· cm‐1. In TCNQ complexes the electrical conductivities are enhanced by one t

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830906

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractPolycarbonates with pendant carbonate groups were synthesized by copolymerization of carbon dioxide and epoxides containing a carbonate substituent using the diethylzinc/water system as catalyst. The polycarbonates underwent acidic and basic hydrolysis to release slowly the compound attached as the pendant group via the carbonate linkage. Other hydrolysis products were glycerol and CO2, but no oligomeric products were formed.

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830907

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractVarious diastereomericN‐protected dipeptide methyl esters were synthesized fromN‐protected racemic amino acids and racemic amino acid methyl esters. Derivatives of alanine, valine, leucine, and phenylalanine were condensed in various solvents including optically active solvents such asO‐acetyl lactic acid ethyl ester,N‐acetyl lactic acid ethyl ester, orN‐acetyl L‐alanine methyl ester. TheN‐protected amino acids were activated by means of 2‐ethoxy‐1‐ethoxycarbonyl‐1,2‐dihydroquinoline (EEDQ), dicyclohexylcarbodiimide and 4‐chlorothiophenol, 1,1‐carbonyldiimidazole, 1‐diethoxyphosphino‐1,3,4‐triazole, chloroacetonitrile, and isobutyl chloroformate. The reaction mixtures containing four stereoisomers were analyzed by means of13C NMR spectroscopy with respect to the mole ratios of the diastereomeric dipeptides. The stereoselectivity of all experiments was low. The number of experiments favoring the formation of L‐L (D‐D) sequences exceeded by far the number of those favoring L‐D (D‐L) sequences. Tripeptide syntheses, conducted under the reaction conditions of various dipeptide syntheses, revealed that the stereoselectivity is influenced by chiral neighboring groups. However, these “penultimate eff

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830908

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractTwo kinds ofN‐thiocarboxyanhydrides ofD,L‐L andD,L‐L were synthesized, 5‐oxo‐2‐thioxo‐1,3‐oxazolidones1a, 1band 1,3‐thiozolidine‐2,5‐diones2a, 2b. Their polymerizations were conducted at 20°C with primary, secondary, and tertiary amines or with potassiumtert‐butylate as initiators. The tacticity of the resulting poly(D,L‐L)s and poly(D,L‐L)s was investigated by means of13C NMR spectra. It was found that under all conditions the formation of isotactic sequences is favoured. The stereoselectivities of all polymerizations were low; the average lengths of isotactic blocks never exceeded 6 monomeric units. The chain growth deviates slightly from the Bernoullian statistics favoring the formation of longer isotactic blocks. WhileD,L‐4‐isopropyl‐2,5‐thiazolidindione (2a) did not polymerize, the polymerization ofD,L‐4‐isopropyl‐5‐oxo‐2‐thioxooxazolidine (1a) (D,L‐L‐NTA) showed under all conditions lower

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830909

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY

摘要:

AbstractThe activated anionic polymerization of ϵ‐caprolactam is strongly affected by LiCl addition to the polymerizing medium. Large variations in the yield of the polymerization products are induced by increasing salt content: both high polymer and cyclic dimer yields sharply decrease as functions of the salt concentration, whereas monomer and (in part) higher oligomers show a relevant increase. Also the production of low molecular weight side products is influenced by LiCl: higher salt concentrations induce the formation of larger amounts of side compounds. Monomer equilibrium data reveal that the salt negatively affects the thermodynamics of polymerization. ΔG 0pvariation as a function of LiCl content shows an increasingly relevant influence of the entropic contribution to the standard free energy change. The effects of LiCl on ring‐ring equilibria are qualitatively interpreted on the basis of both the strong ion‐ion interactions between Li+ions and carbonyl groups and the interchain densificatio

ISSN:0025-116X    

DOI:10.1002/macp.1982.021830910

出版商:Hüthig&Wepf Verlag    

年代:1982

数据来源: WILEY