2577-90-4Relevant articles and documents
Propargyloxycarbonyl and propargyl groups for novel protection of amino, hydroxy, and carboxy functions
Kukase,Fukase,Kusumoto
, p. 1169 - 1170 (1999)
The propargyloxycarbonyl group readily introduced to both amino and hydroxy groups by using propargyl chloroformate is stable to neat TFA but is readily cleaved at ambient temperature by treatment with Co2(CO)8 and TFA in CH2Cl2 via formation of an alkyne-Co complex. The propargyl ester similarly serves as a good protecting group for carboxy functions.
Synthesis and Reactivity of 5-Substituted Furfuryl Carbamates via Oxanorbornadienes
Tekkam, Srinivas,Finn
, p. 2833 - 2836 (2017)
Furfuryl carbamates are labile and require care to be accessed by activating furfuryl alcohols. An alternative oxanorbornadiene (OND)-based strategy is presented for the preparation of 5-R-substituted furfuryl carbamates via the reactions of amines with intermediate OND carbonates. The resulting OND carbamates, which are stable for several months, undergo thiol mediated retro-Diels-Alder reaction to deliver the desired furfuryl carbamates in a single flask. Conditions for the selective hydrolysis of furfuryl carbamates in the presence of tert-butyloxycarbonyl (Boc) groups were identified, and it was shown that furfuryl carbamates can be used as a prodrug handle.
Formation of lanthanide complexes with bipyridine-functionalized amide compounds and their unusually high amide reactivity
Araki,Kawaguchi,Kajikawa,Kaneko,Koshimizu
, p. 2729 - 2736 (1999)
The amide of 6-benzoylamino-6'-L-phenylalanyl-amino-2,2'-bipyridine (1a) was efficiently cleaved at 30°C to generate L-phenylalanine ester in methanol almost quantitatively. The reaction followed the Michaelis-Menten type via the 1:1 1a-Ln3+ complex. The half-life time of the scissile amide bond of the complex was as short as 2 min for the complex. The reactions depended on the structure of the substrates, which require 2,2'-bipyridine with two acylamino side chains at the 6,6'-positions and an amino group at the α-position of the scissile carbonyl. The less reactive 6-6'bis(benzoylamino)-2,2'-bipyridine with lanthanide cations formed 1:1 complexes. The formation constants were on the order of 103-105 cu dm/mole in methanol at 30°C. Coordination of the bipyridine nitrogens and the carbonyl oxygens was demonstrated in chloroform although coordination of the carbonyl oxygens was not seen in methanol.
A green route for the synthesis of a bitter-taste dipeptide combining biocatalysis, heterogeneous metal catalysis and magnetic nanoparticles
Ungaro, Vitor A.,Liria, Cleber W.,Romagna, Carolina D.,Costa, Natália J. S.,Philippot, Karine,Rossi, Liane M.,Machini, M. Teresa
, p. 36449 - 36455 (2015)
There is increasing demand for green technologies to produce high-solubility and low-toxicity compounds with potential application in the food industry. This study aimed to establish a clean, synthetic route for preparing the bitter-taste dipeptide Ala-Phe, a potential substitute for caffeine as a food additive. Synthesis of Z-Ala-Phe-OMe starting from Z-Ala-OH and HCl·Phe-OMe was catalysed by thermolysin at 50 °C in buffer (step 1). Z-Ala-Phe-OMe ester hydrolysis to give Z-Ala-Phe-OH at 37 °C in 30% acetonitrile/buffer was catalysed by α-bovine chymotrypsin (αCT), protease with esterase activity (step 2). Hydrogenation of Z-Ala-Phe to give the desired Ala-Phe was catalysed by C/Pd in methanol (step 3). Steps 2 and 3 were optimized by using the magnetically recoverable recycling enzyme Fe3O4@silica-αCT and the magnetically recoverable metal nanocatalyst Fe3O4@silica-Pd, respectively. This inspiring combination of technologies and the original results demonstrate the suitability of using enzymes, metal catalyst and magnetic nanoparticles for easy, economical, stereoselective, clean production of an important target compound. Besides, they add to the development of peptide chemistry and catalysis.
Chiral N-hydroxybenzamides as potential catalysts for aerobic asymmetric oxidations
Capraro, Maria Grazia,Franchi, Paola,Lanzalunga, Osvaldo,Lapi, Andrea,Lucarini, Marco
, p. 6435 - 6443 (2014)
Chiral N-hydroxybenzamides (1H-3H) have been synthesized as precursors of chiral short-lived N-oxyl radicals 1?-3?. The latter species have been generated by oxidation of 1H-3H with Pb(OAc)4 or hydrogen abstraction from 1H-3H by the tert-butoxyl radical and characterized by UV-vis spectrophotometry and EPR spectroscopy. Through a kinetic study of the hydrogen atom transfer processes promoted by 1?-3? from three chiral benzylic substrates (1-phenylethylamine, 1-phenylethanol, and α-vinylbenzyl alcohol), a moderate chiral discrimination has been found, with selectivity factors 0.5 ≥ kH(S)/kH(R) ≥ 2.
Highly Stable Zr(IV)-Based Metal-Organic Frameworks for Chiral Separation in Reversed-Phase Liquid Chromatography
Jiang, Hong,Yang, Kuiwei,Zhao, Xiangxiang,Zhang, Wenqiang,Liu, Yan,Jiang, Jianwen,Cui, Yong
supporting information, p. 390 - 398 (2021/01/13)
Separation of racemic mixtures is of great importance and interest in chemistry and pharmacology. Porous materials including metal-organic frameworks (MOFs) have been widely explored as chiral stationary phases (CSPs) in chiral resolution. However, it remains a challenge to develop new CSPs for reversed-phase high-performance liquid chromatography (RP-HPLC), which is the most popular chromatographic mode and accounts for over 90% of all separations. Here we demonstrated for the first time that highly stable Zr-based MOFs can be efficient CSPs for RP-HPLC. By elaborately designing and synthesizing three tetracarboxylate ligands of enantiopure 1,1′-biphenyl-20-crown-6, we prepared three chiral porous Zr(IV)-MOFs with the framework formula [Zr6O4(OH)8(H2O)4(L)2]. They share the same flu topological structure but channels of different sizes and display excellent tolerance to water, acid, and base. Chiral crown ether moieties are periodically aligned within the framework channels, allowing for stereoselective recognition of guest molecules via supramolecular interactions. Under acidic aqueous eluent conditions, the Zr-MOF-packed HPLC columns provide high resolution, selectivity, and durability for the separation of a variety of model racemates, including unprotected and protected amino acids and N-containing drugs, which are comparable to or even superior to several commercial chiral columns for HPLC separation. DFT calculations suggest that the Zr-MOF provides a confined microenvironment for chiral crown ethers that dictates the separation selectivity.
Stereoretentive N-Arylation of Amino Acid Esters with Cyclohexanones Utilizing a Continuous-Flow System
Ichitsuka, Tomohiro,Komatsuzaki, Shingo,Masuda, Koichiro,Koumura, Nagatoshi,Sato, Kazuhiko,Kobayashi, Shū
supporting information, p. 10844 - 10848 (2021/05/31)
The N-arylation of chiral amino acid esters with minimal racemization is a challenging transformation because of the sensitivity of the α-stereocenter. A versatile synthetic method was developed to prepare N-arylated amino acid esters using cyclohexanones as aryl sources under continuous-flow conditions. The designed flow system, which consists of a coil reactor and a packed-bed reactor containing a Pd(OH)2/C catalyst, efficiently afforded the desired N-arylated amino acids without significant racemization, accompanied by only small amounts of easily removable co-products (i. e., H2O and alkanes). The efficiency and robustness of this method allowed for the continuous synthesis of the desired product in very high yield and enantiopurity with high space-time yield (74.1 g L?1 h?1) and turnover frequency (5.9 h?1) for at least 3 days.
Continuous flow heterogeneous catalytic reductive aminations under aqueous micellar conditions enabled by an oscillatory plug flow reactor
?tv?s, Sándor B.,Buchholcz, Balázs,Darvas, Ferenc,Kappe, C. Oliver,Novák, Zoltán,Sipos, Gellért,Wernik, Michaela
supporting information, p. 5625 - 5632 (2021/08/16)
Despite the fact that continuous flow processing exhibits well-established technical advances, aqueous micellar chemistry, a field that has proven extremely useful in shifting organic synthesis to sustainable water-based media, has mostly been explored under conventional batch-based conditions. This is particularly because of the fact that the reliable handling of slurries and suspensions in flow has been considered as a significant technical challenge. Herein, we demonstrate that the strategic application of an oscillatory plug flow reactor enables heterogeneous catalytic reductive aminations in aqueous micellar media enhancing mass transport and facilitating process simplicity, stability and scalability. The micellar flow process enabled a broad range of substrates, including amino acid derivatives, to be successfully transformed under reasonably mild conditions utilizing only very low amounts of Pd/C as a readily available heterogeneous catalyst. The preparative capabilities of the process along with the recyclability of the heterogenous catalyst and the aqueous reaction media were also demonstrated. This journal is
Transition Metal-Free N-Arylation of Amino Acid Esters with Diaryliodonium Salts
Kervefors, Gabriella,Kersting, Leonard,Olofsson, Berit
supporting information, p. 5790 - 5795 (2021/03/08)
A transition metal-free approach for the N-arylation of amino acid derivatives has been developed. Key to this method is the use of unsymmetric diaryliodonium salts with anisyl ligands, which proved important to obtain high chemoselectivity and yields. The scope includes the transfer of both electron deficient, electron rich and sterically hindered aryl groups with a variety of different functional groups. Furthermore, a cyclic diaryliodonium salt was successfully employed in the arylation. The N-arylated products were obtained with retained enantiomeric excess.
A General Stereocontrolled Synthesis of Opines through Asymmetric Pd-Catalyzed N-Allylation of Amino Acid Esters
Albat, Dominik,Neud?rfl, J?rg-Martin,Schmalz, Hans-Günther
supporting information, p. 2099 - 2102 (2021/07/22)
A stereo-divergent synthesis of natural and unnatural opines in stereochemically pure form is based on the direct palladium-catalyzed N-allylation of α-amino acid esters (up to 97 % ee or 99 : 1 d.r.) using methyl (E)-2-penten-4-yl carbonate in the presence of only 1 mol% of a catalyst, prepared in-situ from the C2-symmetric diphosphine iPr-MediPhos and [Pd(allyl)Cl]2. Selected target compounds (incl. a derivative of the drug enalapril) were efficiently obtained from the N-allylated intermediates by oxidative cleavage (ozonolysis) of the allylic C=C bond under temporary N-Boc-protection.
