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Keywords = eight-membered lactams

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16 pages, 2033 KB  
Article
A Lewis Acid-Promoted Michael Addition and Ring-Expansion Cascade for the Construction of Nitrogen-Containing Medium-Sized Rings
by Jiaming Wang, Jia Li and Changgui Zhao
Molecules 2023, 28(4), 1650; https://doi.org/10.3390/molecules28041650 - 8 Feb 2023
Cited by 6 | Viewed by 3509
Abstract
A Lewis acid-promoted annulation of azadienes and cyclobutamines was developed. This reaction proceeded through Michael addition and ring-expansion cascade, affording the corresponding nitrogen-containing medium-sized rings with a broad scope in moderate to high yields. The catalytic asymmetric version of this reaction has also [...] Read more.
A Lewis acid-promoted annulation of azadienes and cyclobutamines was developed. This reaction proceeded through Michael addition and ring-expansion cascade, affording the corresponding nitrogen-containing medium-sized rings with a broad scope in moderate to high yields. The catalytic asymmetric version of this reaction has also been explored using a chiral base. Full article
(This article belongs to the Special Issue Catalytic Green Reductions and Oxidations)
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10 pages, 1426 KB  
Article
Efficient Enzymatic Routes for the Synthesis of New Eight-membered Cyclic β-Amino Acid and β-Lactam Enantiomers
by Enikő Forró, Loránd Kiss, Judit Árva and Ferenc Fülöp
Molecules 2017, 22(12), 2211; https://doi.org/10.3390/molecules22122211 - 13 Dec 2017
Cited by 9 | Viewed by 4467
Abstract
Efficient enzymatic resolutions are reported for the preparation of new eight-membered ring-fused enantiomeric β-amino acids [(1R,2S)-9 and (1S,2R)-9] and β-lactams [(1S,8R)-3, (1R,8S)- [...] Read more.
Efficient enzymatic resolutions are reported for the preparation of new eight-membered ring-fused enantiomeric β-amino acids [(1R,2S)-9 and (1S,2R)-9] and β-lactams [(1S,8R)-3, (1R,8S)-3 (1S,8R)-4 and (1R,8S)-7], through asymmetric acylation of (±)-4 (E > 100) or enantioselective hydrolysis (E > 200) of the corresponding inactivated (±)-3 or activated (±)-4 β-lactams, catalyzed by PSIM or CAL-B in an organic solvent. CAL-B-catalyzed ring cleavage of (±)-6 (E > 200) resulted in the unreacted (1S,8R)-6, potential intermediate for the synthesis of enantiomeric anatoxin-a. The best strategies, in view of E, reaction rate and product yields, which underline the importance of substrate engineering, are highlighted. Full article
(This article belongs to the Section Organic Chemistry)
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9 pages, 1386 KB  
Article
Looking Inside the Intramolecular C−H∙∙∙O Hydrogen Bond in Lactams Derived from α-Methylbenzylamine
by Sandra Mejía, Julio M. Hernández-Pérez, Jacinto Sandoval-Lira and Fernando Sartillo-Piscil
Molecules 2017, 22(3), 361; https://doi.org/10.3390/molecules22030361 - 28 Feb 2017
Cited by 14 | Viewed by 6814
Abstract
Recently, strong evidence that supports the presence of an intramolecular C−H···O hydrogen bond in amides derived from the chiral auxiliary α-methylbenzylamine was disclosed. Due to the high importance of this chiral auxiliary in asymmetric synthesis, the inadvertent presence of this C−H···O interaction may [...] Read more.
Recently, strong evidence that supports the presence of an intramolecular C−H···O hydrogen bond in amides derived from the chiral auxiliary α-methylbenzylamine was disclosed. Due to the high importance of this chiral auxiliary in asymmetric synthesis, the inadvertent presence of this C−H···O interaction may lead to new interpretations upon stereochemical models in which this chiral auxiliary is present. Therefore, a series of lactams containing the chiral auxiliary α-methylbenzylamine (from three to eight-membered ring) were theoretically studied at the MP2/cc-pVDZ level of theory with the purpose of studying the origin and nature of the C−Hα···O interaction. NBO analysis revealed that rehybridization at C atom of the C−Hα bond (s-character at C is ~23%) and the subsequent bond polarization are the dominant effect over the orbital interaction energy n(O)→σ*C−Hα (E(2) < 2 kcal/mol), causing an important shortening of the C−Hα bond distance and an increment in the positive charge in the Hα atom. Full article
(This article belongs to the Special Issue Intramolecular Hydrogen Bonding 2017)
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26 pages, 357 KB  
Article
Macrocyclic Pyridyl Polyoxazoles: Structure-Activity Studies of the Aminoalkyl Side-Chain on G-Quadruplex Stabilization and Cytotoxic Activity
by Gifty Blankson, Suzanne G. Rzuczek, Cody Bishop, Daniel S. Pilch, Angela Liu, Leroy Liu, Edmond J. LaVoie and Joseph E. Rice
Molecules 2013, 18(10), 11938-11963; https://doi.org/10.3390/molecules181011938 - 26 Sep 2013
Cited by 7 | Viewed by 7458
Abstract
Pyridyl polyoxazoles are 24-membered macrocyclic lactams comprised of a pyridine, four oxazoles and a phenyl ring. A derivative having a 2-(dimethylamino)ethyl chain attached to the 5-position of the phenyl ring was recently identified as a selective G-quadruplex stabilizer with excellent cytotoxic activity, and [...] Read more.
Pyridyl polyoxazoles are 24-membered macrocyclic lactams comprised of a pyridine, four oxazoles and a phenyl ring. A derivative having a 2-(dimethylamino)ethyl chain attached to the 5-position of the phenyl ring was recently identified as a selective G-quadruplex stabilizer with excellent cytotoxic activity, and good in vivo anticancer activity against a human breast cancer xenograft in mice. Here we detail the synthesis of eight new dimethylamino-substituted pyridyl polyoxazoles in which the point of attachment to the macrocycle, as well as the distance between the amine and the macrocycle are varied. Each compound was evaluated for selective G-quadruplex stabilization and cytotoxic activity. The more active analogs have the amine either directly attached to, or separated from the phenyl ring by two methylene groups. There is a correlation between those macrocycles that are effective ligands for the stabilization of G-quadruplex DNA (DTtran 15.5–24.6 °C) and cytotoxicity as observed in the human tumor cell lines, RPMI 8402 (IC50 0.06–0.50 μM) and KB3-1 (IC50 0.03–0.07 μM). These are highly selective G-quadruplex stabilizers, which should prove especially useful for evaluating both in vitro and in vivo mechanism(s) of biological activity associated with G-quaqdruplex ligands. Full article
(This article belongs to the Special Issue G-Quadruplexes & i-Motif DNA)
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