79069-13-9Relevant academic research and scientific papers
Chiral polyisocyanates from an azomonomer with a very high chiral induction
Mruk, Ralf,Zentel, Rudolf
, p. 185 - 192 (2002)
The synthesis of new chiral polyisocyanates is described. For this purpose a new chiral azobenzene containing monomer with the chiral center in α-position to the isocyanate group was synthesized. The anionic copolymerization was carried out in THF as solvent with potassium cyanide that was complexed by 18-crown-6 as initiator. This allowed a better control of the reaction and thereby the synthesis of polyisocyanates with a fairly low polydispersity. The copolymers show an extremely high transfer of chirality from the chiral side groups to the helical backbone in dilute solution. Copolymers with only 1.6 mol % of chiral side groups show nearly the full optical rotation and exist predominantly in the P-helical conformation. It was found that the isomerization of the azobenzene groups hardly has any influence on the conformation of the helix. Lyotropic liquid crystalline phases were formed from the polymers and 1,2-dichlorobenzene. It could be shown that even polymers with a very low content of chiral side groups (1.6 mol %) form cholesteric phases with a selective reflection in the visible range. The pitch of the cholesteric phase and thereby the wavelength of the selective reflection bands could be reversibly altered by the isomerization of the azobenzene groups.
Fluorinated Olefinic Lactams: The Case of Amino Acids - Preparation and Mechanistic Studies
Bartoszak-Adamska, El?bieta,Go?dyn, Mateusz,Koroniak, Henryk,Koroniak-Szejn, Katarzyna,Salamon-Krokosz, Katarzyna,Siod?a, Tomasz
, (2022/03/17)
Herein, we report the synthesis of analogues of amino acids with a monofluorovinyl moiety. Interestingly, we have found that cyclization of the obtained products proceeds easily in all cases. The cyclization process has not previously been observed at this reaction stage, and such fluorinated lactams derived from phenylalanine, valine, alanine have not been described before.
Synthesis and Characterization of Optically Pure Gamma-PNA Backbones by SIBX-Mediated Reductive Amination
Periyalagan, Alagarsamy,Kim, Yong-Tae,Hong, In Seok
, p. 1304 - 1309 (2021/08/09)
Chiral peptide nucleic acid (PNA) is a derivative of regular PNA by introducing a chiral center to its backbone, and is known to bind more strongly to DNA or RNA than regular PNA. In particular, in the case of a γ-backbone, the L isomer stabilizes the PNA/DNA duplex, and the D-isomer has the opposite effect. Therefore, the synthesis of an optically pure γ-backbone is very important. Here, we report a novel synthetic strategy for the suppression of epimerization during the synthesis of the γ-PNA backbone. A stabilized form of 2-iodoxybenzoic acid (SIBX) was used as an oxidative reagent in the key intermediate of the N-Boc-amino acetaldehyde synthesis. This paper reports (1) the synthesis and comparison of three different γ-PNA backbones (lysine, alanine, and glutamate) by three different synthetic routes (SIBX, lithium aluminum hydride, and Red-Al) and (2) the determination of chiral purity from their derivative compounds. The enantiomeric excess purity of SIBX-mediated γ-PNA backbones was determined to be more than 99.4%, as ascertained by the high-performance liquid chromatography (HPLC) chromatogram on a standard RP-C18 column. It is comparatively higher than that of the other methods examined in this work.
Urea based foldamers
Yoo, Sung Hyun,Li, Bo,Dolain, Christel,Pasco, Morgane,Guichard, Gilles
, p. 59 - 92 (2021/06/25)
N,N′-linked oligoureas are a class of enantiopure, sequence-defined peptidomimetic oligomers without amino acids that form well-defined and predictable helical structures akin to the peptide α-helix. Oligourea-based foldamers combine a number of features—such as synthetic accessibility, sequence modularity, and folding fidelity—that bode well for their use in a range of applications from medicinal chemistry to catalysis. Moreover, it was recently recognized that this synthetic helical backbone can be combined with regular peptides to generate helically folded peptide-oligourea hybrids that display additional features in terms of helix mimicry and protein-surface recognition properties. Here we provide detailed protocols for the preparation of requested monomers and for the synthesis and purification of homo-oligoureas and peptide-oligourea hybrids.
Thiamine hydrochloride as a recyclable organocatalyst for the efficient and chemoselective N-tert-butyloxycarbonylation of amines
Ingale, Ajit P.,Garad, Dnyaneshwar N.,Ukale, Dattatraya,Thorat, Nitin M.,Shinde, Sandeep V.
supporting information, p. 3791 - 3804 (2021/11/04)
Thiamin hydrochloride promoted highly efficient and ecofriendly approach has been described for the chemoselective N-tert-butyloxycarbonylation of amines under solvent-free conditions at ambient temperature. The demonstrated approach has been applicable for the N-Boc protection of variety of aliphatic, aryl, heteroaryl amines. The chemoselective protection of amino group occurs in chiral amines and amino alcohol without racemization in high yield. Thiamin hydrochloride is stable, economical, easy to handle and environmentally friendly.
Ultrasound promoted environmentally benign, highly efficient, and chemoselective N-tert-butyloxycarbonylation of amines by reusable sulfated polyborate
Pise, Ashok S.,Ingale, Ajit P.,Dalvi, Navnath R.
supporting information, p. 3768 - 3780 (2021/10/26)
The sulfated polyborate catalyzed an efficient and chemoselective N-tert-butyloxycarbonylation of amines under ultrasonic irradiation is developed. A broad substrate scope has been demonstrated for N-Boc protection of various primary/secondary amines. It allows converting several aliphatic/aryl/heteroaryl amines, amino alcohol, aminoester, and chiral amines to their N-Boc-protected derivatives under solvent-free conditions with excellent yields. The protocol has several advantages such as easy catalyst, and product isolation, short reaction time, excellent yields, outstanding chemoselectivity, and catalyst recyclability, among others. This makes the process practicable, economical, and environmentally benign.
Sulfated tungstate: A highly efficient, recyclable and ecofriendly catalyst for chemoselective N-tert butyloxycarbonylation of amines under the solvent-free conditions
Ingale, Ajit P.,Shinde, Sandeep V.,Thorat, Nitin M.
supporting information, p. 2528 - 2543 (2021/07/02)
Sulfated tungstate catalyzed an efficient and ecofriendly protocol has been described for the chemoselective N-tert-butyloxycarbonylation of amines under the solvent-free conditions at room temperature. The variety of functionalized aliphatic, aromatic and heteroaromatic amines efficiently undergoes the N-tert-butyloxycarbonylation under the developed protocol. The aminoalcohol, aminophenol, aminoester as well as various chiral amines underwent the chemoselective N-Boc protection under the optimized reaction condition. The rapid reaction rate, mild conditions, very good functional group tolerance, excellent yield, solvent-free, easy recovery products and excellent catalyst recyclability are the advantages of this protocol. This makes the protocol feasible, economical and environmentally benign.
Nanoceria as an efficient and green catalyst for the chemoselective N-tert-butyloxycarbonylation of amines under the solvent-free conditions
Garad, Dnyaneshwar N.,Ingale, Ajit P.,Shinde, Sandeep V.,Ukale, Dattatraya
supporting information, p. 1656 - 1668 (2021/04/05)
Nanocerium oxide mediated an efficient and green protocol has been described for the chemoselective N-tert-butyloxycarbonylation of amines under the solvent-free conditions at ambient temperature. Various aliphatic, aromatic and heteroaromatic amines were protected using developed protocol and several functional groups such as alcohol, phenol and ester were well tolerated under these conditions. The rapid reaction rate, mild conditions, very good functional group tolerance, excellent yield, solvent-free, easy recovery products and excellent catalyst recyclability are the advantages of this protocol. This makes the protocol feasible, economical and environmentally benign.
Cobalt-Catalyzed Desymmetric Isomerization of Exocyclic Olefins
Lan, Yu,Liu, Qiang,Liu, Shihan,Liu, Xufang,Rong, Xianle
supporting information, p. 20633 - 20639 (2021/12/17)
Chiral cyclic olefins, 1-methylcyclohexenes, are versatile building blocks for the synthesis of pharmaceuticals and natural products. Despite the prevalence of these structural motifs, the development of efficient synthetic methods remains an unmet challenge. Herein we report a novel desymmetric isomerization of exocyclic olefins using a series of newly designed chiral cobalt catalysts, which enables a straightforward construction of chiral 1-methylcyclohexenes with diversified functionalities. The synthetic utility of this methodology is highlighted by a concise and enantioselective synthesis of a natural product, β-bisabolene. The versatility of the reaction products is further demonstrated by multifarious derivatizations.
Expansion of substrate scope for nitroxyl radical/copper-catalyzed aerobic oxidation of primary alcohols: A guideline for catalyst selection
Iwabuchi, Yoshiharu,Nagasawa, Shota,Sasaki, Ryota,Sasano, Yusuke,Yamaichi, Aoto
, p. 488 - 497 (2021/05/27)
Four distinctive sets of optimum nitroxyl radical/copper salt/additive catalyst combinations have been identified for accommodating the aerobic oxidation of various types of primary alcohols to their corresponding aldehydes. Interestingly, less nucleophilic catalysts exhibited higher catalytic activities for the oxidation of particular primary allylic and propargylic alcohols to give α,β-unsaturated aldehydes that function as competent Michael acceptors. The optimum conditions identified herein were successful in the oxidation of various types of primary alcohols, including unprotected amino alcohols and divalent-sulfur-containing alcohols in good-to-high yields. Moreover, N-protected alaninol, an inefficient substrate in the nitroxyl radical/ copper-catalyzed aerobic oxidation, was oxidized in good yield. On the basis of the optimization results, a guideline for catalyst selection has been established.
