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1.
Shuhei Yamada Koichi Koga Atsushi Sudo Mitsuaki Goto Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2013,51(17):3726-3731
We report a useful synthetic method of polypeptides using a series of urethane derivative of α‐amino acids (l ‐leucine, l ‐phenylalanine, l ‐valine, l ‐alanine, l ‐isoleucine, l ‐methionine), which are readily synthesized by N‐carbamoylation of tetrabutylammonium salts of α‐amino acids with diphenyl carbonate. Heating these urethane derivatives in N,N‐dimethylacetamide in the presence of n‐butylamine successfully gave the corresponding polypeptides with well‐defined structures through polycondensation with the elimination of phenol and CO2. The matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry investigation showed that the resulting polypeptides had an n‐BuNH2‐incorporated initiating end and an amino group at propagating end. These results strongly indicated that primary amines served as an initiator in this polycondensation system. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3726–3731 相似文献
2.
Yasutaka Kamei Atsushi Nagai Atsushi Sudo Haruo Nishida Kiyoshi Kikukawa Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2008,46(8):2649-2657
A series of activated urethane‐type derivatives of γ‐benzyl‐L ‐glutamate were synthesized, and their potential as monomers for polypeptide synthesis was investigated. The derivatives of the focus of this work were a series of N‐aryloxycarbonyl‐γ‐benzyl‐L ‐glutamate 1 , of which aryl groups were phenyl, 4‐chlorophenyl, and 4‐nitrophenyl. These urethanes 1 were reactive in polar solvents such as dimethylsulfoxide, N,N‐dimethylformamide (DMF), and N,N‐dimethylacetamide (DMAc), and were efficiently converted into poly(γ‐benzyl‐L ‐glutamate) (poly(BLG)) under mild conditions; at 60 °C without addition of any catalyst. Among the three urethanes, that having 4‐nitrophenoxycarbonyl group 1c was the most reactive to give poly(BLG) efficiently, as was expected from the highly electron deficient nature of the nitrophenoxycarbonyl group. On the other hand, the urethane 1a having phenoxycarbonyl group was also efficiently converted into poly(BLG), in spite of the intrinsically less electrophilicity of the phenoxycarbonyl group. In addition, the successful formation of poly(BLG) by the reaction of 1a favored its diluted concentration (0.1 M) much more than 2.0 M, the optimum initial concentration for 1c . 1H NMR spectroscopic analyses of the reactions in situ revealed that the predominant pathway from 1 to poly(BLG) involved the intramolecular cyclization of 1 into the corresponding N‐carboxyanhydride, with release of phenol and its successive ring‐opening polymerization with release of carbon dioxide. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2649–2657, 2008 相似文献
3.
Fumio Sanda Taizo Fujiyama Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2001,39(5):732-741
α‐Methyl glutamic acid (L ‐L )‐, (L ‐D )‐, (D ‐L )‐, and (D ‐D )‐γ‐dimers were synthesized from L ‐ and D ‐glutamic acids, and the obtained dimers were subjected to polycondensation with 1‐(3‐dimethylaminopropyl)‐3‐ethylcarbodiimide hydrochloride and 1‐hydroxybenzotriazole hydrate as condensation reagents. Poly‐γ‐glutamic acid (γ‐PGA) methyl ester with the number‐average molecular weights of 5000∼20,000 were obtained by polycondensation in N,N‐dimethylformamide in 44∼91% yields. The polycondensation of (L ‐L )‐ and (D ‐D )‐dimers afforded the polymers with much larger |[α]D | compared with the corresponding dimers. The polymer could be transformed into γ‐PGA by alkaline hydrolysis or transesterification into α‐benzyl ester followed by hydrogenation. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 732–741, 2001 相似文献
4.
Kazuyuki Hattori Takashi Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2012,50(21):4524-4531
A stereoregular 2‐amino‐glycan composed of a mannosamine residue was prepared by ring‐opening polymerization of anhydro sugars. Two different monomers, 1,6‐anhydro‐2‐azido‐mannose derivative ( 3 ) and 1,6‐anhydro‐2‐(N, N‐dibenzylamino)‐mannose derivative ( 6 ), were synthesized and polymerized. Although 3 gave merely oligomers, 6 was promptly polymerized into high polymers of the number‐average molecular weight (Mn) of 2.3 × 104 to 2.9 × 104 with 1,6‐α stereoregularity. The differences of polymerizability of 3 and 6 from those of the corresponding glucose homologs were discussed. It was found that an N‐benzyl group is exceedingly suitable for protecting an amino group in the polymerization of anhydro sugars of a mannosamine type. The simultaneous removal of O‐ and N‐benzyl groups of the resulting polymers was achieved by using sodium in liquid ammonia to produce the first 2‐amino‐glycan, poly‐(1→6)‐α‐D ‐mannosamine, having high molecular weight through ring‐opening polymerization of anhydro sugars.© 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
5.
Hans R. Kricheldorf Colin V. Lossow Nino Lomadze Gert Schwarz 《Journal of polymer science. Part A, Polymer chemistry》2008,46(12):4012-4020
The NCAs of the following five amino acids were polymerized in bulk at 120 °C without addition of a catalyst or initiator: sarcosine (Sar), L ‐alanine (L ‐Ala), D ,L ‐phenylalanine (D ,L ‐Phe), D ,L ‐leucine (D ,L ‐Leu) and D ,L ‐valine (D,L ‐Val). The virgin reaction products were characterized by viscosity measurements 13C NMR spectroscopy and MALDI‐TOF mass spectrometry. In addition to numerous low molar mass byproducts cyclic polypeptides were formed as the main reaction products in the mass range above 800 Da. Two types of cyclic oligo‐ and polypeptides were detected in all cases with exception of sarcosine NCA, which only yielded one class of cyclic polypeptides. The efficient formation of cyclic oligo‐ and polypeptides explains why high molar mass polymers cannot be obtained by thermal polymerizations of α‐amino acid NCAs. Various polymerization mechanisms were discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4012–4020, 2008 相似文献
6.
Koichi Koga Atsushi Sudo Haruo Nishida Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2009,47(15):3839-3844
A new convenient synthesis of N‐carboxyanhydrides (NCAs) of α‐amino acids was achieved by selective cyclization of urethane derivatives of α‐amino acids. The urethanes were readily synthesized via N‐carbamoylation of α‐amino acids by bis(4‐nitrophenyl)carbonate quantitatively. These urethanes having 4‐nitrophenoxy moiety were tolerant to air and moisture to allow their facile purification and storage. When the obtained urethanes were heated in 2‐butanone at 60 °C, they underwent the selective cyclization via intramolecular nucleophilic attack of the carboxyl moiety to the urethane moiety with releasing 4‐nitrophenol, leading to the successful formation of the corresponding NCAs. Addition of carboxylic acids remarkably stabilized the formed NCAs during the reaction, allowing their isolation in high yields. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3839–3844, 2009 相似文献
7.
Erwin Abdul Rahim Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2006,44(2):810-819
Novel optically active amino acid based polyacetylenes bearing eugenol and fluorene moieties were synthesized, and their properties, including chiroptical ones, were analyzed. N‐[1‐(3,4‐Dimethoxyphenyl)‐2‐propyloxycarbonyl]‐L ‐alanine N′‐propargylamide ( 1 ), N‐[1‐(3,4‐dimethoxyphenyl)‐2‐propyloxycarbonyl]‐L ‐alanine propargyl ester ( 2 ), N‐(9‐fluorenylmethoxycarbonyl)‐L ‐alanine N′‐propargylamide ( 3 ), and N‐(9‐fluorenylmethoxycarbonyl)‐L ‐alanine propargyl ester ( 4 ) were polymerized with a rhodium‐zwitterion catalyst in tetrahydrofuran to afford the corresponding polymers with moderate molecular weights ranging from 10,800 to 17,300 in good yields. Because of the large specific rotation and circular dichroism (CD) signal, it was concluded that the poly(N‐propargylamide)s [poly( 1 ) and poly( 3 )] took a helical structure with a predominantly one‐handed screw sense. The solvent and temperature could tune the helical structure of poly( 1 ). On the other hand, the poly(propargyl ester)s [poly( 2 ) and poly( 4 )] exhibited only small specific rotations and CD signals. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 810–819, 2006 相似文献
8.
Naser Foroughifar Akbar Mobinikhaledi Sattar Ebrahimi Mohammad Ali Bodaghi Fard Hassan Moghanian 《中国化学会会志》2009,56(5):1043-1047
Some new and optically active 1,2,4‐triazolo thiadiazoles bearing N‐phthaloyl‐l ‐amino acids were synthesized by reaction of 4‐amino‐5‐(3‐ or 4‐)pyridyl‐3‐mercapto‐(4H)‐1,2,4‐triazoles with N‐phthaloyl‐l ‐amino acids in the presence of phosphorus oxychloride. All the newly synthesized compounds were confirmed by IR, 1H NMR, 13C NMR and elemental analysis. 相似文献
9.
Ruiyuan Liu Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2008,46(12):4183-4192
Novel 4‐ethynylphthaloyl amino acid esters carrying different terminal groups, 4‐ethynylphthaloyl glycine (1S,2R,5S)‐menthyl ester ( 1 ), 4‐ethynylphthaloyl glycine (1R,2S,5R)‐menthyl ester ( 2 ), 4‐ethynylphthaloyl L ‐leucine methyl ester ( 3 ), 4‐ethynylphthaloyl L ‐leucine (1S,2R,5S)‐menthyl ester ( 4 ), 4‐ethynylphthaloyl L ‐leucine (1R,2S,5R)‐menthyl ester ( 5 ) were synthesized and polymerized with a rhodium catalyst. Polymers with high molecular weights were obtained in 71–92% yields. The helical conformation of the polymers could be tuned by the chirality of the amino acid connected to the backbone, together with the chirality and bulkiness of the terminal pendent groups. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4183–4192, 2008 相似文献
10.
Zhening Yang Tianwen Bai Jun Ling Youqing Shen 《Journal of polymer science. Part A, Polymer chemistry》2019,57(8):907-916
Differing from the moisture‐sensitive α‐amino acid N‐carboxyanhydrides (AA‐NCAs) monomers, N‐phenoxycarbonyl α‐amino acids (AA‐NPCs) can be prepared and stored in open air. In this contribution, we report that the controlled polymerizations of AA‐NPC monomers of O‐tert‐butyl‐dl ‐serine (BRS‐NPC), Nε‐benzyloxycarbonyl‐l ‐lysine (ZLL‐NPC) and Nε‐trifluoroacetyl‐l ‐lysine (FLL‐NPC) initiated by amines are surprisingly able to tolerate common nucleophilic impurities such as water and alcohols at a level of monomer concentration. The structures of polypeptides synthesized in the presence of water or alcohols agree well with the designed ones in the case of repeated chain extensions. Detailed mechanism study and density functional theory calculation reveal that the low concentration of AA‐NCA and the high activity of amines are the key factors to the controllability of AA‐NPC polymerizations. The water‐ and alcohol‐tolerant property in polymerizations of AA‐NPCs encourages the following studies on unprotected (phenolic) hydroxyl groups containing AA‐NPCs. The controllable polymerizations of N‐phenoxycarbonyl l ‐tyrosine (LT‐NPC) and N‐phenoxycarbonyl S‐(3‐hydroxypropyl)‐l ‐cysteine (HLC‐NPC) initiated by amines are confirmed and reported for the first time, which extends the library of AA‐NPCs and polypeptides as well. All the universality of library, the convenience of monomer preparation, and the controllability and water‐ and alcohol‐tolerant property of polymerization of AA‐NPCs significantly enhance the feasibility of polypeptide synthesis, making AA‐NPC approach a promising synthetic method of polypeptides. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 907–916 相似文献
11.
Hans R. Kricheldorf Colin Von Lossow Gert Schwarz 《Journal of polymer science. Part A, Polymer chemistry》2005,43(22):5690-5698
The N‐carboxyanhydrides (NCAs) of sarcosine (Sar), D ,L ‐leucine (D ,L ‐Leu), D ,L ‐phenylalanine (D ,L ‐Phe), and L ‐alanine (L ‐Ala) were polymerized in dioxane. Imidazole served as initiator and the NCA/initiator ratio was varied from 1/1 to 40/1. The isolated polypeptides were characterized by 1H NMR spectroscopy, by MALDI‐TOF mass spectrometry, by viscosity measurements, and by SEC measurements in the case of poly(sarcosine). Cyclic oligopeptides were found in all reaction products and in the case of polySar, poly(D ,L ‐Leu), and poly(D ,L ‐Phe) the cycles were the main products. In the case of poly(L ‐Ala), rapid precipitation of β‐sheet lamellaes prevented efficient cyclizations and stabilized imidazolide endgroups. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5690–5698, 2005 相似文献
12.
Hui Peng Jun Ling Yinghong Zhu Lixin You Zhiquan Shen 《Journal of polymer science. Part A, Polymer chemistry》2012,50(15):3016-3029
In this work, rare earth tris(borohydride) complexes, Ln(BH4)3(THF)3 (Ln = Sc, Y, La, and Dy), have been used to catalyze the ring‐opening polymerization of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (BLG NCA). All the catalysts show high activities and the resulting poly(γ‐benzyl‐L ‐glutamate)s (PBLGs) are recovered with high yields (≥90%). The molecular weights (MWs) of PBLG can be controlled by the molar ratios of monomer to catalyst, and the MW distributions (MWDs) are relatively narrow (as low as 1.16) depending on the rare earth metals and reaction temperatures. Block copolypeptides can be easily synthesized by the sequential addition of two monomers. The obtained P(γ‐benzyl‐L ‐glutamate‐b‐ε‐carbobenzoxy‐L ‐lysine) [P(BLG‐b‐BLL)] and P(γ‐benzyl‐L ‐glutamate‐b‐alanine) [P(BLG‐b‐ALA)] have been well characterized by NMR, gel permeation chromatography, and differential scanning calorimetry measurements. A random copolymer P(BLG‐co‐BLL) with a narrow MWD of 1.07 has also been synthesized. The polymerization mechanisms have been investigated in detail. The results show that both nucleophilic attack at the 5‐CO of NCA and deprotonation of 3‐NH of NCA in the initiation process take place simultaneously, resulting in two active centers, that is, an yttrium ALA carbamate derivative [H2BOCH2(CH)NHC(O)OLn? ] and a N‐yttriumlated ALA NCA. Propagation then proceeds on these centers via both normal monomer insertion and polycondensation. After termination, two kinds of telechelic polypeptide chains, that is, α‐hydroxyl‐ω‐aminotelechelic chains and α‐carboxylic‐ω‐aminotelechelic ones, are formed as characterized by MALDI‐TOF MS, 1H NMR, 13C NMR, 1H–1H COSY, and 1H–13C HMQC measurements. By decreasing the reaction temperature, the normal monomer insertion pathway can be exclusively selected, forming an unprecedented α‐hydroxyl‐ω‐aminotelechelic polypeptide. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
13.
Ren‐Shen Lee Jen‐Ming Yang 《Journal of polymer science. Part A, Polymer chemistry》2001,39(5):724-731
A series of novel copolymers of trans‐4‐hydroxy‐L ‐proline (Hpr) and α‐ hydroxy acids [D,L ‐mandelic acid (DLMA) and D,L ‐lactic acid (DLLA)] were synthesized via direct melt copolymerization with stannous octoate as a catalyst. These new copolymers had pendant amine functional groups along the polymer backbone chain. The optimal reaction conditions for the synthesis of the copolymers were obtained with 4 wt % stannous octoate at 140 °C under vacuum for 16 h. The synthesized copolymers were characterized by IR spectrophotometry, proton nuclear magnetic resonance, differential scanning calorimetry, and Ubbelohde viscometry. The effects of the kinds of comonomers and the comonomer molar ratio on the polycondensation and glass‐transition temperature (Tg) were investigated. The Tg's of the copolymers shifted to lower temperatures with an increasing comonomer molar ratio. As expected, the Tg's of the N‐Z‐Hpr/DLMA copolymers were higher than the N‐Z‐Hpr/DLLA copolymers, the pendant groups on the monomers (N‐Z‐Hpr) became larger and more flexible, and the Tg's of the resulting polymers declined. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 724–731, 2001 相似文献
14.
Haichao Zhao Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2007,45(2):253-261
Novel L ‐alanine and L ‐glutamic acid derivatized, carbazole‐containing N‐propargylamides [N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide and N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] were synthesized and polymerized with (nbd)Rh+[η6‐C6H5B?(C6H5)3] (nbd = norbornadiene) as a catalyst to obtain the corresponding polymers with moderate molecular weights in high yields. Polarimetry, circular dichroism, and ultraviolet–visible spectroscopy studies revealed that both poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] took a helical structure with a predominantly one‐handed screw sense in tetrahydrofuran, CHCl3, and CH2Cl2. The helix content of poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] could be tuned by heat or the addition of a protic solvent, and the helical sense of poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] was inverted by heat in CHCl3 or in mixtures of tetrahydrofuran and CH2Cl2. Poly[N‐(9‐carbazolyl) ethyloxycarbonyl‐L ‐alanine N′‐propargylamide] and poly[N‐(9‐carbazolyl)ethyloxycarbonyl‐L ‐glutamic acid‐γ‐benzyl ester N′‐propargylamide] also took a helical structure in film states. They showed small fluorescence in comparison with the monomers and redox activity based on carbazole. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 253–261, 2007 相似文献
15.
Hans R. Kricheldorf Colin Von Lossow Gert Schwarz 《Journal of polymer science. Part A, Polymer chemistry》2006,44(15):4680-4695
Sarcosine N‐carboxyanhydride, D,L ‐alanine N‐carboxyanhydride, D,L ‐phenylalanine N‐carboxyanhydride, and D,L ‐leucine N‐carboxyanhydride were polymerized with pyridine or N‐ethyldiisopropylamine as the catalyst. With pyridine, cyclic oligo‐ and polypeptides were obtained in addition to water‐initiated or water‐terminated chains. The cyclopeptides were the main products in the case of sarcosine N‐carboxyanhydride and D,L ‐phenylalanine N‐carboxyanhydride. The fraction of cycles was particularly high when N‐methylpyrrolidone was used as the reaction medium. These results suggested the existence of a pyridine‐catalyzed zwitterionic mechanism. However, cyclopeptides were also obtained with N‐ethyldiisopropylamine as the catalyst. In this case, N‐deprotonation of N‐carboxyanhydrides, followed by the formation of N‐acyl N‐carboxyanhydride chain ends, was the most likely initiation mechanism. Various chain‐growth mechanisms were examined. In the case of γ‐benzyl ester‐L ‐glutamate N‐carboxyanhydride, side reactions such as the formation of pyroglutamoyl end groups were detected. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4680–4695, 2006 相似文献
16.
Macroinitiator‐amino terminated poly(ethylene glycol) (PEG) (NH2‐PEO‐NH2) was prepared by converting both terminal hydroxyl groups of PEG to more reactive primary amino groups. The synthetic route involved reactions of chloridize, phthalimide and finally hydrazinolysis. Furthermore, poly(γ‐benzyl‐L ‐glutamate)‐poly(ethylene oxide)‐poly(γ‐benzyl‐L ‐glutamate) (PBLG‐PEO‐PBLG) triblock copolymer was synthesized by polymerization of γ‐benzyl‐L ‐glutamate N‐carboxyanhydride (Bz‐L‐GluNCA) using NH2‐PEO‐NH2 as macroinitiator. The resultant NH2‐PEO‐NH2 and triblock copolymer were characterized by FT‐IR, 1H‐NMR and gel permeation chromatography (GPC) techniques. The results demonstrated that the degree of amination of the NH2‐PEO‐NH2 could be up to 1.95. The molecular weight of the PBLG‐PEO‐PBLG triblock copolymer could be adjusted easily by controlling the molar ratio of Bz‐L ‐Glu NCA to the macroinitiator NH2‐PEO‐NH2. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
17.
Andrea Wamsley Pasit Phiasivongsa Bhaskara Jasti Xiaoling Li 《Journal of polymer science. Part A, Polymer chemistry》2006,44(14):4328-4337
Three different characterization methods—13C NMR spectroscopy, a terminal terpolymerization model, and a probability analysis based on the Poisson distribution—were used to determine the microstructure of random terpolymers. The methods were used to determine the amino acid sequence distribution of random terpolymers prepared from the polymerization of N‐carboxyanhydrides that contained L ‐leucine, β‐benzyl‐L ‐aspartate, and L ‐valine. Poly(L ‐leucine‐L ‐aspartic acid‐L ‐valine) [poly(LDV)] was designed as a target specific substrate for the α4β1 integrin that recognizes the tripeptide sequence leucine‐aspartic acid‐valine (LDV). The presence of the tripeptide sequence LDV within the polymer was determined to be eight LDV triad sequences on average in terpolymers of approximately 100 kDa. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4328–4337, 2006 相似文献
18.
Sutthira Sutthasupa Kayo Terada Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2006,44(18):5337-5343
Amino acid‐derived novel norbornene derivatives, N,N′‐(endo‐bicyclo[2.2.1] hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐alanine methyl ester (NBA), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐leucine methyl ester (NBL), N,N′‐(endo‐bicyclo[2.2.1]hept‐5‐en‐2,3‐diyldicarbonyl) bis‐L ‐phenylalanine methyl ester (NBF) were synthesized and polymerized using the Grubbs 2nd generation ruthenium (Ru) catalyst. Although NBA, NBL, and NBF did not undergo homopolymerization, they underwent copolymerization with norbornene (NB) to give the copolymers with Mn ranging from 5200 to 38,100. The maximum incorporation ratio of the amino acid‐based unit was 9%, and the cis contents of the main chain were 54–66%. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5337–5343, 2006 相似文献
19.
Tadamasa Nemoto Daisuke Ando Kensuke Naka Yoshiki Chujo 《Journal of polymer science. Part A, Polymer chemistry》2007,45(3):543-547
To develop a novel polycondensation method for the preparation of poly (amino acid)s, we screened a transition metal or a rare‐earth triflate as a Lewis acid for the polycondensation of activated amino acid esters in N,N‐dimethylformamide solutions at room temperature. The polymerizations of 4‐nitrophenyl L ‐leucinate ( 1a ) and 4‐nitrophenyl L ‐valinate ( 1b ) scarcely proceeded without any Lewis acid at room temperature. In the presence of 5 mol % metal triflates, especially scandium(III) trifluoromethanesulfonate, the polymerizations of both monomers were promoted effectively. The products, which were collected by the reaction mixture being poured into water, were recognized as poly(L ‐valine)s by Fourier transform infrared spectroscopy, gel permeation chromatography analysis, and 1H NMR spectroscopy. These results showed that a metal triflate as a Lewis acid could coordinate to a carbonyl oxygen of activated L ‐valinate and L ‐leucinate even in a highly polar solvent, such as N,N‐dimethylformamide; therefore, the polymerizations of activated L ‐valinate and L ‐leucinate were promoted. Because steric hindrance derived from the isobutyl group in 1b was less than that of the isopropyl unit in 1a , the effect of the metals was not as sensitive for the polymerization of 1b . © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 543–547, 2007 相似文献
20.
Haichao Zhao Fumio Sanda Toshio Masuda 《Journal of polymer science. Part A, Polymer chemistry》2005,43(21):5168-5176
Aspartic acid‐based novel poly(N‐propargylamides), i.e., poly[N‐(α‐tert‐butoxycarbonyl)‐L ‐aspartic acid β‐benzyl ester N′‐propargylamide] [poly( 1 )] and poly[N‐(α‐tert‐butoxycarbonyl)‐L ‐aspartic acid α‐benzyl ester N′‐propargylamide] [poly( 2 )] with moderate molecular weights were synthesized by the polymerization of the corresponding monomers 1 and 2 catalyzed with (nbd)Rh+[η6‐C6H5B?(C6H5)3] in CHCl3 at 30 °C for 2 h in high yields. The chiroptical studies revealed that poly( 1 ) took a helical structure in DMF, while poly( 2 ) did not in DMF but did in CH2Cl2, CHCl3, and toluene. The helicity of poly( 1 ) and poly( 2 ) could be tuned by temperature and solvents. Poly( 2 ) underwent solvent‐driven switch of helical sense, accompanying the change of the tightness. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5168–5176, 2005 相似文献