- Enzymatic Synthesis and Stereocomplex Formation of Chiral Polyester Containing Long-Chain Aliphatic Alcohol Backbone
-
Herein we demonstrated a novel lipase-catalyzed synthesis of isotactic D-/L-poly(aspartate-octanediol) ester containing long chain alcohols backbone and discovered their stereocomplex feature with an increased Tm for the first time. Simple desi
- Xia, Bo,Zhang, Yu,Zhu, Qiaoyan,Lin, Xianfu,Wu, Qi
-
-
Read Online
- Substrate Engineering in Lipase-Catalyzed Selective Polymerization of d -/ l -Aspartates and Diols to Prepare Helical Chiral Polyester
-
The synthesis of optically pure polymers is one of the most challenging tasks in polymer chemistry. Herein, Novozym 435 (Lipase B from Candida antarctica, immobilized on Lewatit VP OC 1600)-catalyzed polycondensation between d-/l-aspartic acid (Asp) diester and diols for the preparation of helical chiral polyesters was reported. Compared with d-Asp diesters, the fast-reacting l-Asp diesters easily reacted with diols to provide a series of chiral polyesters containing N-substitutional l-Asp repeating units. Besides amino acid configuration, N-substituent side chains and the chain length of diols were also investigated and optimized. It was found that bulky acyl N-substitutional groups like N-Boc and N-Cbz were more favorable for this polymerization than small ones probably due to competitively binding of these small acyl groups into the active site of Novozym 435. The highest molecular weight can reach up to 39.5 × 103 g/mol (Mw, D = 1.64). Moreover, the slow-reacting d-Asp diesters were also successfully polymerized by modifying the substrate structure to create a "nonchiral"condensation environment artificially. These enantiocomplementary chiral polyesters are thermally stable and have specific helical structures, which was confirmed by circular dichroism (CD) spectra, scanning electron microscope (SEM), and molecular calculation.
- Zhang, Yu,Xia, Bo,Li, Yanyan,Lin, Xianfu,Wu, Qi
-
p. 918 - 926
(2021/02/01)
-
- Silyl Group-Directed 6-exo-dig Iodocyclization of Homopropargylic Carbamates and Amides
-
Iodocyclization of silyl group-substituted homopropargylic carbamates and amides proceeded via 6-exo-dig mode to afford 6-vinylene-4,5-dihydro-1,3-oxazines in moderate to quantitative yields. This is the first report for silyl group-solely directed iodocy
- Okitsu, Takashi,Nakahigashi, Hikaru,Sugihara, Ryosuke,Fukuda, Ikki,Tsuji, Saki,In, Yasuko,Wada, Akimori
-
p. 18638 - 18642
(2018/12/04)
-
- Economical synthesis of tert-butyl (S)-3-aminopyrrolidine-1-carboxylate from L-aspartic acid
-
3-Aminopyrrolidine building block was used as the intermediate for many pharmaceutically active substances. Starting from L-aspartic acid, optically active (S)-tert-butyl-3-aminopyrrolidine-1-carboxylate was synthesized, and the reaction conditions were optimized in each step. The procedure of each step was discussed in detail and could be useful for the industrial preparation. This process was featured by readily available starting material, mild reaction conditions, easy work-up, and economy.
- Han, Zhi-Jian,Li, Yang-Bing,Gu, Bao-Hong,Li, Yu-Min,Chen, Hao
-
p. 2452 - 2456
(2018/10/20)
-
- A direct route to 2,2,5-trisubstituted pyrrolidines of relevance to kaitocephalin
-
2,2,5-Trisubstituted pyrrolidines of relevance to the core of kaitocephalin are readily available by an oxime ring closure using substrates derived from aspartic acid.
- Chandan, Nandkishkor,Moloney, Mark G.
-
supporting information
p. 1987 - 1990
(2013/04/10)
-
- Efficient and selective cleavage of the t-butoxycarbonyl group from di-t-butylimidodicarbonate using catalytic bismuth(III) bromide in acetonitrile
-
Di-t-butylimidodicarbonates can be chemoselectively and efficiently deprotected to the corresponding mono-BOC-protected amines in high yields using a catalytic amount of bismuth(III) bromide in acetonitrile at room temperature. This method is mild and compatible with the presence of a wide range of functional and other protecting groups in the substrates, such as TBDMS, MOM and mono-BOC or Cbz-protected amines, etc. The method has advantages of ease of operation and use of nontoxic and inexpensive catalyst.
- Zheng, Jianlong,Yin, Biaolin,Huang, Wenming,Li, Xiaopeng,Yao, Hequan,Liu, Zhaogui,Zhang, Jiancun,Jiang, Sheng
-
scheme or table
p. 5094 - 5097
(2009/12/01)
-
- CERTAIN CHEMICAL ENTITIES, COMPOSITIONS, AND METHODS
-
Compounds useful for treating cellular proliferative diseases and disorders by modulating the activity of one or more mitotic kinesins are disclosed.
- -
-
Page/Page column 56
(2010/11/27)
-
- Regioselective opening of N-Cbz glutamic and aspartic anhydrides with carbon nucleophiles
-
Depending on the experimental conditions, aspartic and glutamic anhydrides can be opened regioselectively with Grignard reagents, thus giving access to different isomers of chiral amino-ketoesters.
- Deguest, Geoffrey,Bischoff, Laurent,Fruit, Corinne,Marsais, Francis
-
p. 2120 - 2125
(2007/10/03)
-
- Radical cyanocarbonylation using alkyl allyl sulfone precursors
-
Acyl cyanides have been prepared by the three-component coupling reactions comprised of alkyl allyl sulfones, carbon monoxide, and p-tolylsulfonyl cyanide under tin-free radical reaction conditions. Georg Thieme Verlag Stuttgart.
- Kim, Sangmo,Cho, Chang Ho,Kim, Sunggak,Uenoyama, Yoshitaka,Ryu, Ilhyong
-
p. 3160 - 3162
(2007/10/03)
-
- CERTAIN CHEMICAL ENTITIES, COMPOSITIONS, AND METHODS
-
Compounds useful for treating cellular proliferative diseases and disorders by modulating the activity of one or more mitotic kinesins are disclosed.
- -
-
Page/Page column 268-270
(2008/06/13)
-
- First Practical Protection of α-Amino Acids as N, N-Benzyloxycarbamoyl Derivatives
-
The consecutive treatment of N-Cbz amino protected compounds with LiHMDS and CbzCl provides a practical method for the preparation of N,N-benzyloxycarbamoyl (N,N-di-Cbz) derivatives in good yield. When α-amino acids are used the protection occurs without racemization. The method is compatible with a wide range of other functional and protecting groups. The procedure is also valid for the synthesis of mixed N,N-carbamoyl derivatives.
- Hernandez, J. Nicolas,Martin, Victor S.
-
p. 3590 - 3592
(2007/10/03)
-
- 3-(Imidazolyl)-2-aminopropanoic acids
-
Compounds according to formula (I) wherein n is 1-4, R1 is optionally substituted C1-6 alkyl, C2-6 alkenyl, or C2-6 alkynyl, Heterocycle, Aromatic heterocycle, Aryl or hydrogen and R2, R3,
- -
-
-
- Cleavage of benzyloxycarbonyl-5-oxazolidinones to α-benzyloxycarbonylamino-α-alkyl esters by alcohols and sodium hydrogen carbonate
-
The reaction of benzyloxycarbonyl-5-oxazolidinones with alcohols and sodium hydrogen carbonate to afford the corresponding benzyloxycarbonyl esters is described.
- Allevi, Pietro,Cighetti, Giuliana,Anastasia, Mario
-
p. 5319 - 5321
(2007/10/03)
-
- Zirconocene-catalyzed epoxy ester - ortho ester rearrangement: A new method for the protection of polyfunctionalized carboxylic acids and the asymmetric synthesis of ortho esters
-
In situ prepared Cp2(CI)Zr+ catalyzes the formation of ortho esters from epoxy esters. Acid-sensitive α-amino and α-hydroxy acid derivatives are converted in high yield to 2,7,8- trioxabicyclo[3.2.1]octanes (ABO-esters) using this protocol. This strategy is complementary to the OBO-ester technology, and orthogonal methods for the deprotection of ABO- and OBO-esters have been developed. The syntheses of the mushroom components (S)-γ- hydroxyleucine lactone and (S)-α-vinylglycine underline the value of ABO-ester protective group strategy. Using chiral epoxy alcohol derivatives, the first convenient and general asymmetric synthesis of bicyclic ortho esters has been achieved.
- Wipf, Peter,Wenjing, Xu,Hongyong, Kim,Takahashi, Hidenori
-
p. 16575 - 16596
(2007/10/03)
-
- Practical synthesis of (S)-3-(p-nitrobenzyloxy-carbonylamino)pyrrolidine and its related compounds from L-aspartic acid
-
An efficient method for the preparation of (S)-3-aminopyrrolidine derivatives was developed starting from L-aspartic acid, which involves an efficient formation of a pyrrolidine-ring from allylamine and a practical Pd/C-catalyzed cleavage of N-allyl prote
- Tomori, Hiroshi,Shibutani, Kuniko,Ogura, Katsuyuki
-
p. 213 - 225
(2007/10/03)
-