- Modular Synthesis of Carbazole-Substituted Phthalimides as Potential Photocatalysts
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The modular synthesis of carbazole functionalized phthalimides (PIs) and their applicability as catalyst in selected photocatalytic transformations are reported. The developed synthetic approach provides high variability of phthalimide considering that the synthesis of the phthalimide core can be easily performed. Starting from fluorophthalic acid anhydrides, the corresponding fluorophthalimides were prepared with various amines, and the fluoro function ensured the introduction of carbazoles into the phthalimide framework through aromatic nucleophilic substitution. Besides the synthetic developments, some of the carbazolyl phthalimides were tested in four different photocatalytic transformations, which showed attractive and comparable activity to the known 4-CzIPN and noble metal complexes.
- F?ldesi, Tamás,Gonda, Zsombor,Nagy, Bálint,Novák, Zoltán
-
supporting information
(2021/11/22)
-
- Design, synthesis and biological evaluation of new bivalent quinazoline analogues as IAP antagonists
-
We recently reported the biological evaluations of monovalent IAP antagonist 7 with good potency (MDA-MB-231, IC50 = 19 nM). In an effort to increase cellular activity and improve favorable drug-like properties, we newly designed and synthesized bivalent analogues based on quinazoline structure of 7. Optimization of cellular potency and CYP inhibition led to the identification of 27, which showed dramatic increase of over 100-fold (IC50 = 0.14 nM) and caused substantial tumor regressions in MDA-MB-231 xenograft model. These results strongly support 27 as a promising bivalent antagonist for the development of an effective anti-tumor approaches.
- Bae, Inhwan,Kim, Daejin,Choi, Jaeyul,Kim, Jisook,Kim, Minjeong,Park, Bokyung,Kim, Young Hoon,Ahn, Young Gil,Hyung Kim, Ha,Kim, Dae Kyong
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supporting information
(2021/01/26)
-
- Synthesis and evaluation of in Vivo anti-hypothermic effect of the N- And C-terminus modified thyrotropin-releasing hormone mimetic: [(4S,5S)-(5-methyl-2-oxooxazolidine-4-yl)-carbonyl]-[3-(thiazol-4-yl)-L-alanyl]-L-prolinamide
-
We explored orally effective thyrotropin-releasing hormone (TRH) mimetics, which show high central nervous system effects in structure–activity relationship studies based on in vivo antagonistic activity on reserpine-induced hypothermia (anti-hypothermic effect) in mice starting from TRH. This led us to the TRH mimetic: [(4S,5S)-(5-methyl-2-oxooxazolidine-4-yl)carbonyl]-[3-(thiazol-4-yl)-L-alanyl]-L-prolinamide 1, which shows a higher anti-hypothermic effect compared with that of TRH after oral administration. We next attempted further chemical modification of the N- and C-terminus of 1 to find more orally effective TRH mimetics. As a result, we obtained several N- and C-terminus modified TRH mimetics which showed high anti-hypothermic effects.
- Kobayashi, Naotake,Sato, Norihito,Sugita, Katsuji,Kihara, Tsuyoshi,Koike, Katsumi,Sugawara, Tamio,Tada, Yukio,Yoshikawa, Takayoshi
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p. 314 - 324
(2021/04/30)
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- Synthesis of Amide Enol Carbamates and Carbonates through Cu(OTf)2-Catalyzed Reactions of Ynamides with t-Butyl Carbamates/Carbonates
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A highly regioselective approach to access amide enol carbamates and carbonates 5a-5c′, 7a-7h, and 9 was developed through Cu(OTf)2-catalyzed reactions of ynamides 4 with t-butyl carbamates 2 and 8 and t-butyl carbonates 6. Moreover, this strategy was successfully applied to generate amide enol carbamates 11a-11s and 14a-14f from imides 10 and 13 with ynamides through an N-Boc cleavage-addition ring-opening process. A range of substituents was amenable to this transformation, and the desired amide enol carbamates and carbonates were obtained in moderate to good yields.
- Han, Pan,Mao, Zhuo-Ya,Li, Ming,Si, Chang-Mei,Wei, Bang-Guo,Lin, Guo-Qiang
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p. 4740 - 4752
(2020/04/30)
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- A Ni–Ir Dual Photocatalytic Liebeskind Coupling of Sulfonium Salts for the Synthesis of 2-Benzylpyrrolidines
-
A new method has been developed for the synthesis of 2-benzylpyrrolidines utilizing cross-coupling and photoredox catalysis. Using a well-established dual Ni–Ir system, we were able to successfully couple benzylsulfonium salts with proline utilizing radical forming through CO2 extrusion. This enabled the simple one-step synthesis of 2-benzylpyrrolidines from stable, inexpensive starting materials.
- Varga, Bálint,Gonda, Zsombor,Tóth, Balázs L.,Kotschy, András,Novák, Zoltán
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p. 1466 - 1471
(2019/11/03)
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- Enantioselective Radical Cyclization for Construction of 5-Membered Ring Structures by Metalloradical C-H Alkylation
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Radical cyclization represents a powerful strategy for construction of ring structures. Traditional radical cyclization, which is based on radical addition as the key step, necessitates the use of unsaturated substrates. Guided by the concept of metalloradical catalysis, a different mode of radical cyclization that can employ saturated C-H substrates is demonstrated through the development of a Co(II)-based system for catalytic activation of aliphatic diazo compounds for enantioselective radical alkylation of various C(sp3)-H bonds. It allows for efficient construction of chiral pyrrolidines and other valuable 5-membered cyclic compounds. This alternative strategy of radical cyclization provides a new retrosynthetic paradigm to prepare five-membered cyclic molecules from readily available open-chain aldehydes through the union of C-H and C=O elements for C-C bond formation.
- Wang, Yong,Wen, Xin,Cui, Xin,Zhang, X. Peter
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p. 4792 - 4796
(2018/04/17)
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- Zn-Catalyzed tert-Butyl Nicotinate-Directed Amide Cleavage as a Biomimic of Metallo-Exopeptidase Activity
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A two-step catalytic amide-to-ester transformation of primary amides under mild reaction conditions has been developed. A tert-butyl nicotinate (tBu nic) directing group is easily introduced onto primary amides via Pd-catalyzed amidation with tert-butyl 2-chloronicotinate. A weak base (Cs2CO3 or K2CO3) at 40-50 °C can be used provided that 1,1′-bis(dicyclohexylphosphino)ferrocene is selected as ligand. The tBu nic activated amides subsequently allow Zn(OAc)2-catalyzed nonsolvolytic alcoholysis in tBuOAc at 40-60 °C under neutral reaction conditions. The activation mechanism is biomimetic: the C3-ester substituent of the pyridine in the directing group populates the trans-conformer suitable for Zn-chelation, C=Oamide-Zn-Ndirecting group, and Zn-coordinated alcohol is additionally activated as a nucleophile by hydrogen bonding with the acetate ligand of the catalyst. Additionally, the acetate ligand assists in intramolecular O-to-N proton transfer. The chemoselectivity versus other functional groups and compatibility with challenging reaction partners, such as peptides, sugars, and sterols, illustrates the synthetic applicability of this two-step amide cleavage method. The tBu nic amides do not require purification before cleavage. Preliminary experiments also indicate that other weak nucleophiles can be used such as (hetero)arylamines (transamidation) as exemplified by 8-aminoquinoline.
- Wybon, Clarence C. D.,Mensch, Carl,Hollanders, Charlie,Gadais, Charlène,Herrebout, Wouter A.,Ballet, Steven,Maes, Bert U. W.
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p. 203 - 218
(2018/01/17)
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- PROCESS FOR THE CATALYTIC DIRECTED CLEAVAGE OF AMIDE-CONTAINING COMPOUNDS
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The present invention relates to a catalytic method for the conversion of amide-containing compouds by means of a build-in directing group and upon the action of a heteronucleophilic compound (in se an amine (RNH2 or RNHR') or an alcohol (ROH) or a thiol (RSH)) in the presence of a metal catalyst to respectively esters, thioesters, carbonates, thiocarbonates and to what is defined as amide-containing compounds (such as carboxamides, urea, carbamates, thiocarbamates). The present invention also relates to these amide-containing compounds having a build-in directing group (DG), as well as the use of such directing groups in the catalytic directed cleavage of N-DG amides with the use of heteronucleophiles (in se an amine (RNH2 or RNHR') or an alcohol (ROH) or thiol (RSH)).
- -
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Page/Page column 53
(2017/04/11)
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- Copper nanoparticles catalyzed N-H functionalization: An efficient solvent-free N-tert-butyloxycarbonylation strategy
-
A chemoselective transformation of amines to their tert-butyloxycarbonyl (Boc) protected derivatives (NBoc) is described using Cu-NPs under solvent-free conditions. Simple method, rapid reaction rate, mild conditions, tolerance of a wide range of functional groups, excellent yield, ease recovery and high catalytic turnover are the salient features of this approach. tert-Butyloxycarbonylation of chiral amino acid esters and amino alcohols were performed without racemization.
- Deb, Barnali,Debnath, Sudipto,Deb, Anindita,Maiti, Dilip K.,Majumdar, Swapan
-
supporting information
p. 629 - 633
(2017/01/25)
-
- Levorotatory meptazinol prodrug as well as preparation method and purpose thereof
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The invention provides a levorotatory meptazinol prodrug as well as a preparation method and a purpose thereof, wherein the levorotatory meptazinol prodrug is a compound as shown in a formula I or a stereoisomer, a geometrical isomer, a tautomer, oxynitride, a hydrate, a solvate, a metabolite or a pharmaceutically acceptable salt of the compound as shown in the formula I. The compound is low in hepatic first pass effect and high in bioavailability; a medicine which uses the compound as an active component can be used for treating a neurodegenerative disease or various kinds of acute and chronic pain, such as a wound, postoperative, obstetrical and cancer pain, hemicrania, neuropathic pain and the like.
- -
-
Paragraph 0183; 0184; 0186; 0187
(2017/07/19)
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- Catalytic Synthesis of N-Heterocycles via Direct C(sp3)-H Amination Using an Air-Stable Iron(III) Species with a Redox-Active Ligand
-
Coordination of FeCl3 to the redox-active pyridine-aminophenol ligand NNOH2 in the presence of base and under aerobic conditions generates FeCl2(NNOISQ) (1), featuring high-spin FeIII and an NNOISQ radical ligand. The complex has an overall S = 2 spin state, as deduced from experimental and computational data. The ligand-centered radical couples antiferromagnetically with the Fe center. Readily available, well-defined, and air-stable 1 catalyzes the challenging intramolecular direct C(sp3)-H amination of unactivated organic azides to generate a range of saturated N-heterocycles with the highest turnover number (TON) (1 mol% of 1, 12 h, TON = 62; 0.1 mol% of 1, 7 days, TON = 620) reported to date. The catalyst is easily recycled without noticeable loss of catalytic activity. A detailed kinetic study for C(sp3)-H amination of 1-azido-4-phenylbutane (S1) revealed zero order in the azide substrate and first order in both the catalyst and Boc2O. A cationic iron complex, generated from the neutral precatalyst upon reaction with Boc2O, is proposed as the catalytically active species.
- Bagh, Bidraha,Broere, Dani?l L. J.,Sinha, Vivek,Kuijpers, Petrus F.,Van Leest, Nicolaas P.,De Bruin, Bas,Demeshko, Serhiy,Siegler, Maxime A.,Van Der Vlugt, Jarl Ivar
-
supporting information
p. 5117 - 5124
(2017/05/04)
-
- Iminium Catalysis inside a Self-Assembled Supramolecular Capsule: Modulation of Enantiomeric Excess
-
The noncovalent combination of a supramolecular host with iminium organocatalysis is described. Due to cation–π interactions the reactive iminium species is held inside the host and reacts in this confined environment. The products formed differ up to 92 % ee from the control experiments without added host. A model rationalizing the observed difference is presented.
- Br?uer, Thomas M.,Zhang, Qi,Tiefenbacher, Konrad
-
supporting information
p. 7698 - 7701
(2016/07/07)
-
- Convenient and Simple Esterification in Continuous-Flow Systems using g-DMAP
-
The utility and applicability of polyethylene-g-polyacrylic acid-immobilized dimethylaminopyridine (g-DMAP) as a catalyst in a continuous-flow system were investigated for decarboxylative esterification. High catalytic activity toward acylation was provided by g-DMAP containing a flexible grafted-polymer structure. During decarboxylation, carboxylic acids and alcohols were converted cleanly using di-tert-butyl dicarbonate (Boc2O) as a coupling reagent, which reduced by-products. In addition, the use of Boc2O resulted in the formation of tert-butyl esters. These esterifications dramatically reduced the reaction time under continuous-flow conditions, with a residence time of approximately 2 min. This highly efficient esterification procedure will provide more practical industrial applications.
- Okuno, Yoshinori,Isomura, Shigeki,Sugamata, Anna,Tamahori, Kaoru,Fukuhara, Ami,Kashiwagi, Miyu,Kitagawa, Yuuichi,Kasai, Emiri,Takeda, Kazuyoshi
-
p. 3587 - 3589
(2015/11/17)
-
- General solvent-free highly selective N-tert-butyloxycarbonylation strategy using protic ionic liquid as an efficient catalyst
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A simple, rapid and solvent-free protocol is described for the chemo-selective transformation of amines to tert-butyloxycarbonyl protected derivatives (NHBoc) using Boc2O and imidazolium trifluoroacetate protic ionic liquid (5-20 mol%). Unwanted side products such as isocyanate, urea or N,N-di-Boc were not detected. The scope of the protection strategy was successfully explored for substrate alcohols, phenols and thiol at elevated temperatures. Optically pure amino acids, amino acid esters and amino alcohols were efficiently converted to the corresponding N-Boc protected derivatives in excellent yields without racemization at the chiral center. The distinct advantages of this method are: operational simplicity, cleaner reaction, high selectivity, excellent yield, rapid reaction convergence, easy preparation and recyclability of the catalyst.
- Majumdar, Swapan,De, Jhinuk,Chakraborty, Ankita,Maiti, Dilip K.
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p. 24544 - 24550
(2014/07/07)
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- Zn(OTf)2-promoted chemoselective esterification of hydroxyl group bearing carboxylic acids
-
Selective esterification of aliphatic and aromatic carboxylic acids with various alcohols is studied using triphenylphosphine, I2, and a catalytic amount of Zn(OTf)2. Use of this catalyst allows the formation of esters at a faster rate with good to excellent yield by activating the in situ generated acyloxyphosphonium ion intermediate. During the esterification process, both their aromatic and aliphatic hydroxyl groups are fully preserved from transesterification. The results show that the bulkiness and the reactivity of this doubly activated intermediate III control the selectivity and the rate of the reaction, respectively. The method is also useful for direct amidation reactions.
- Mamidi, Narsimha,Manna, Debasis
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p. 2386 - 2396
(2013/05/21)
-
- Synthesis and evaluation of C8-substituted 4.5-spiro lactams as Glycogen Phosphorylase a inhibitors
-
An effective synthesis of 4.5-spiro lactams 28/29, has been completed in nine steps with an overall yield of 5.8%. The 4.5-spiro lactams were made from 2-allyl-Cbz-Pro-OMe 21, which was converted into the corresponding alcohol 22 via a hindered borane reaction with (2-methylbutyl)2borane. Subsequent Swern oxidation of 22 gave novel aldehyde 23. Aldehyde 23 was treated under Bucherer-Bergs reaction conditions to give hydantoin 26, which was opened to the corresponding amino acid 30 using di-tert-butyl dicarbonate and DMAP followed by hydrolysis. Treatment of amino acid 30 with acidic methanol gave 4.5-spiro lactams 28/29. Only 4.5-spiro lactam 29 displayed moderate activity against GPa with an IC50 of 241 μM.
- Loughlin, Wendy A.,Schweiker, Stephanie S.,Jenkins, Ian D.,Henderson, Luke C.
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p. 1576 - 1582
(2013/03/29)
-
- Dimethylbut-2-ynedioate mediated esterification of acids via sp3 C-N bond cleavage of benzylic tertiary amines
-
A straightforward synthetic transformation of tertiary amines to the esterification of equimolar amounts of acids was demonstrated in this manuscript. The present protocol can be regarded as a straightforward synthetic transformation of tertiary amines to the esterification of equimolar amounts of acid. Moreover, the reaction is fundamentally new chemistry for the sp 3 C-N bond cleavage coupled with esterification. The esterification reaction conditions are very mild and functional group-tolerated, such as hydrosilanes, alcohols, phenol, and amino acids. A mechanism is proposed in which the tertiary amine reacts with dimethyl but-2-ynedioate to form zwitterionic salt, and then the zwitterionic intermediate subsequently accept hydrogen to assist the nucleophilic attack of oxygen atom of carboxyl group at the benzyl group of tertiary amine, while a separate reaction pathway leads to esterification.
- Shen, Hao,Lu, Xing,Jiang, Ke-Zhi,Yang, Ke-Fang,Lu, Yixin,Zheng, Zhan-Jiang,Lai, Guo-Qiao,Xu, Li-Wen
-
supporting information
p. 8916 - 8923
(2012/10/29)
-
- A metal-free oxidative esterification of the benzyl C-H bond
-
An efficient metal-free oxidative esterification of benzyl C-H bonds was developed. Using tetrabutylammonium iodide as catalyst and tert-butyl hydroperoxide as co-oxidant, benzylic substrates could react smoothly with various carboxylic acids to give the esters with good to excellent yields. The method was also suitable for the O-protection of N-Boc amino acids. The reaction mechanism was primarily investigated and a radical process was proposed. Copyright
- Feng, Jie,Liang, Shuai,Chen, Shan-Yong,Zhang, Ji,Fu, Song-Sen,Yu, Xiao-Qi
-
experimental part
p. 1287 - 1292
(2012/06/15)
-
- QUINOLINE OR QUINAZOLINE DERIVATIVES WITH APOPTOSIS INDUCING ACTIVITY ON CELLS
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Provided is a pharmaceutical composition comprising, as an active ingredient, a quinoline or quinazoline derivative of formula (I), a pharmaceutically acceptable salt, an isomer, a hydrate, and a solvate thereof, which is effective in the prevention and treatment of a cancer, inflammation, autoimmune diseases or neurodegenerative disorders which are induced by the overexpression of inhibitor of apoptosis proteins (IAPs).
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Page/Page column 21
(2012/03/26)
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- Benzyl prolinate derivatives as novel selective KCC2 blockers
-
The discovery and optimization of a novel class of selective submicromolar KCC2 blockers is described. Details of synthesis and SAR are given together with ADME properties of selected compounds. A methylsulfone residue on the R1 phenyl group im
- Pégurier, Cécile,Bosman, Nathalie,Collart, Philippe,Delporte, Marie-Laure,Leclercq, Karine,Lengelé, Sébastien,Kanduluru, Ananda Kumar,Meunier, Stéphane,Pacico, Nathalie,Vadali, Lakshmana Rao,Wagner, Alain,Wolff, Christian,Provins, Laurent
-
scheme or table
p. 2542 - 2545
(2010/07/04)
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- A simple procedure for the esterification of alcohols with sodium carboxylate salts using 1-tosylimidazole (TsIm)
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An efficient and selective method for esterification of alcohols using N-(p-toluenesulfonyl)imidazole (TsIm) is described. In this method, alcohols are refluxed with a mixture of RCO2Na (R: alkyl and aryl), TsIm, and triethylamine in the presence of catalytic amounts of tetra-n-butylammonium iodide (TBAI) in DMF to afford the corresponding esters in good yields. This methodology is highly efficient for various structurally diverse alcohols with selectivity for ROH: 1° > 2° > 3°.
- Soltani Rad, Mohammad Navid,Behrouz, Somayeh,Faghihi, Mohammad Ali,Khalafi-Nezhad, Ali
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p. 1115 - 1120
(2008/09/17)
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- Domino catalysis in the direct conversion of carboxylic acids to esters
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The combined use of high concentration conditions, auxiliary bases, and new catalysts allows for the rapid synthesis of sterically hindered carboxylic acid esters at room temperature. Mechanistic analysis indicates the intermediate formation of acid anhydrides and subsequent rate-limiting transformation to the ester products.
- Held,Von Den Hoff,Stephenson,Zipse
-
supporting information; experimental part
p. 1891 - 1900
(2009/08/07)
-
- Carboline-3-carboxylic acid modified related sequences of Ala-Arg-Pro-Ala-Lys, their synthesis and use as thromobolytic agent
-
The present invention relates to the protected intermediates and the deprotected products of P6A, related to the protected pseudopeptides introducing the protected intermediateds of P6A to 3S-(2-Boc)-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid and the deprotected pseudopeptides, related to the protected pseudopeptides introducing the protected intermediateds of P6A to 3S-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid benzyl ester, related to the methods for their preparation, and related to their use as the thrombolytic agents.
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Page/Page column 9-10
(2010/02/11)
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- Histone deacetylase inhibitors and process for producing the same
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Compounds represented by formula (1) have strong inhibitory activity that is selective towards HDAC1 and HDAC4. Therefore, the compounds of the present invention are useful as pharmaceutical agents for treating or preventing diseases caused by HDAC1 and HDAC4.
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Page/Page column 9
(2008/06/13)
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- Mild one-pot conversion of carboxylic acids to amides or esters with Ph3P/trichloroisocyanuric acid
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The reaction of trichloroisocyanuric acid (TCICA) and triphenylphosphine in the presence of a carboxylic acid results in the in situ formation of the corresponding acid chloride under mild conditions. Subsequent addition of amines or alcohols, in the presence of a tertiary amine affords the corresponding amides, or esters, in good to excellent yields. The methodology was applied to the synthesis of a dipeptide.
- Rodrigues, Rogério Da C.,Barros, Igor M. A.,Lima, Edson L. S.
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p. 5945 - 5947
(2007/10/03)
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- A Convenient Protocol for the Esterification of Carboxylic Acids with Alcohols in the Presence of di-t-Butyl Dicarbonate
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Stoichiometric mixtures of carboxylic acids and primary or secondary alkyl alcohols are cleanly converted into their corresponding esters by treatment with di-t-butyl dicarbonate [(BOC)2O] in the presence of catalytic amounts of N,N′-dimethylaminopyridine (DMAP). This convenient procedure provides a general access to a broad variety of esters including those bearing highly sensitive functional groups such as phenol esters or BOC-groups. Purification of the products is particularly easy since the byproducts t-BuOH and CO2 are volatile - a great advantage over the standard DCC/DMAP method.
- Goo?en, Lukas J.,D?hring, Arno
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p. 263 - 266
(2007/10/03)
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- Lewis Acids as Highly Efficient Catalysts for the Decarboxylative Esterification of Carboxylic Acids with Dialkyl Dicarbonates
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Mild Lewis acids such as Mg(ClO4)2 show a new level of catalytic activity for the decarboxylative esterification of carboxylic acids with commercially available dialkyl dicarbonates. In the presence of as little as one mol % Mg(ClO4)2 catalyst, carboxylic acids can thus easily and near quantitatively be protected at room temperature, e.g., as methyl, benzyl, or t-butyl esters. Only volatile by-products are released so that the purification of the products is particularly easy. Many sensitive functionalities are tolerated, including even phenol esters, or free hydroxy and BOC groups.
- Goossen,Doehring
-
p. 943 - 947
(2007/10/03)
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- Soluble alpha-amino acid salts in acetonitrile: practical technology for the production of some dipeptides.
-
Alpha-amino acids are soluble in acetonitrile when treated with phosphazene bases. As a result, the protection/deprotection events that are usually required for peptide coupling reactions can be minimized. This is illustrated in the synthesis of the important angiotensin-converting enzyme (ACE) inhibitor enalapril. [reaction: see text]
- Palomo, Claudio,Palomo, Antonio L,Palomo, Francisco,Mielgo, Antonia
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p. 4005 - 4008
(2007/10/03)
-
- Use of parallel-synthesis combinatorial libraries for rapid identification of potent FKBP12 inhibitors
-
Using simple, inexpensive equipment, we have used solution-phase parallel synthesis to rapidly prepare hundreds of sulfonamide- and urea-containing FKBP inhibitors, resulting in rapid identification of extremely potent compounds in these series.
- Choi, Chi,Li, Jia-He,Vaal, Mark,Thomas, Christine,Limburg, David,Wu, Yong-Qian,Chen, Yi,Soni, Raj,Scott, Chad,Ross, Douglas T.,Guo, Hong,Howorth, Pamela,Valentine, Heather,Liang, Shi,Spicer, Dawn,Fuller, Mike,Steiner, Joseph,Hamilton, Gregory S.
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p. 1421 - 1428
(2007/10/03)
-
- 1-Ethyl 2-halopyridinium salts, highly efficient coupling reagents for hindered peptide synthesis both in solution and the solid-phase
-
1-Ethyl-2-halopyridinium salts, BEP, FEP, BEPH and FEPH, were synthesized and proved to be very effective for the synthesis of hindered peptides containing N-methylated or C(α),C(α)-dialkylated amino acid residues. HPLC monitoring of model reactions indicated that these pyridinium salts demonstrated higher reactivities, lower racemization than the commonly used halogenated uronium and phosphonium salts. The efficiency of these pyridinium type coupling reagents was further proved by the synthesis of a series of hindered oligopeptides and active esters with good yields and convenient workup. The 8-11 tetrapeptide fragment of Cyclosporin A (CsA) and the pentapeptide moiety of Dolastatin 15 were also successfully synthesized using these pyridinium salts. The efficiency of these pyridinium type coupling reagents for SPPS was also demonstrated by the solid-phase synthesis of the extremely hindered 8-11 peptide segment of CsA and the linear undecapeptide of CsO. The mechanism of the pyridinium salt mediated coupling reactions was also studied by 1H NMR, IR and HPLC. It was proposed that the major reactive intermediates were the corresponding acyl halide and acyloxypyridinium salts of the N-protected amino acid or peptide. (C) 2000 Elsevier Science Ltd.
- Li, Peng,Xu, Jie-Cheng
-
p. 8119 - 8131
(2007/10/03)
-
- Rational design and synthesis of unsaturated 2,5-dioxopiperazine derivatives as potential protein tyrosine kinase inhibitors
-
The first general method for the synthesis of a library of trifunctionalized (Z)-3-alkylidene-2,5-piperazinediones as potential protein tyrosine kinase inhibitors from commercially available amino compounds, α- keto acids and aldehydes using a novel cyclization/cleavage strategy on solid support is described.
- Li, Wen-Ren,Peng, Shao-Zheng
-
p. 7373 - 7376
(2007/10/03)
-
- Design and synthesis of SH3 domain binding ligands: Modifications of the consensus sequence XPpXP
-
Spirolactam-baSed Pro-Pro mimetics incorporated in the consensus sequence XPpXP, lead to effective nonpeptidic ligands of SH3 domains.
- Witter, David J.,Famiglietti, Sara J.,Gambier, John C.,Castelhano, Arlindo L.
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p. 3137 - 3142
(2007/10/03)
-
- Secondary effects in flexible hydrogen bonding networks
-
Extension of Jorgensen's secondary interaction hypothesis to conformationally flexible systems has been examined. The results indicate that secondary interactions between covalently adjacent hydrogen bonding groups are as important as secondary interactions between hydrogen bonding groups brought together by the primary interactions.
- Gardner, Robb R.,Gellman, Samuel H.
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p. 9881 - 9890
(2007/10/03)
-
- Dicarbonates: Convenient 4-dimethylaminopyridine catalyzed esterification reagents
-
The DMAP (4-dimethylaminopyridine) catalyzed reaction of dialkyl dicarbonates la-e and carboxylic acids 2 afforded the corresponding esters 5 in good yield.
- Takeda,Akiyama,Nakamura,Takizawa,Mizuno,Takayanagi,Harigaya
-
p. 1063 - 1066
(2007/10/02)
-