Molecular structure, orbital structure, and relative stability of conformational isomers of 2-phenyl-5-trifluoroacetylpyrrole and its 1-vinyl derivative, according to data obtained by MNDO and MINDO/3 methods

1990 ◽  
Vol 39 (8) ◽  
pp. 1617-1624
Author(s):  
V. A. Shagun ◽  
N. I. Golovanova ◽  
S. E. Korostova ◽  
B. A. Trofimov
Keyword(s):  
Molecular Structure ◽  
Relative Stability ◽  
Orbital Structure ◽  
Conformational Isomers ◽  
Vinyl Derivative

Total Synthesis of the Antitumor Depsipeptide FE399 and its S-Benzyl Derivative: A Macrolactamization Approach

2020 ◽  
Author(s):  
Takayuki Tonoi ◽  
Miyuki Ikeda ◽  
Teruyuki Sato ◽  
Ryo Kawahara ◽  
Takatsugu Murata ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Total Synthesis ◽  
Natural Product ◽  
Condensation Reaction ◽  
Practical Method ◽  
Equilibrium Mixture ◽  
Conformational Isomers ◽  
Single Isomer

<div>An efficient and practical method for the synthesis of (9R,14R,17R)-FE399, a novel antitumor bicyclic depsipeptide, was developed. A 2-methyl-6-nitrobenzoic anhydride (MNBA)-mediated dehydration condensation reaction was effectively employed for the formation of the 16-membered macrocyclic depsipeptide moiety of FE399. FE399 was found to exist as an inseparable equilibrium mixture of conformational isomers; the mixture was quantitatively transformed into the corresponding S-benzyl product and isolated as a single isomer. Thus, we could confirm that the molecular structure of FE399 obtained by this method is identical to that of the natural product.</div>

Investigation of Structural Properties of Heteropropellane Compounds by ab initio methods

2000 ◽  
Vol 2000 (2) ◽  
pp. 93-95 ◽  
Author(s):  
Ali Ebrahimi ◽  
Farzad Deyhimi ◽  
Hosein Roohi
Keyword(s):  
Molecular Structure ◽  
Ab Initio ◽  
Ground State ◽  
Relative Stability ◽  
Density Functional ◽  
Ab Initio Methods ◽  
Inversion Barrier ◽  
Barrier Energy ◽  
Density Functional Methods ◽  
Functional Methods

Molecular structure and relative stability of the ground state of [1.1.1] propellane, various [1.1.1] heteropropellane compounds and also their respective hydrogenated bicyclo compounds along with inversion barrier energy of nitrogen and its corresponding transition state in some of these compounds have been determined using ab initio molecular orbital and hybrid HF-density functional methods.

Total Synthesis of the Antitumor Depsipeptide FE399 and its S-Benzyl Derivative: A Macrolactamization Approach

2020 ◽  
Author(s):  
Takayuki Tonoi ◽  
Miyuki Ikeda ◽  
Teruyuki Sato ◽  
Takehiko Inohana ◽  
Ryo Kawahara ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Total Synthesis ◽  
Natural Product ◽  
Condensation Reaction ◽  
Practical Method ◽  
Equilibrium Mixture ◽  
Conformational Isomers ◽  
Single Isomer

<div>An efficient and practical method for the synthesis of (9R,14R,17R)-FE399, a novel antitumor bicyclic depsipeptide, was developed. A 2-methyl-6-nitrobenzoic anhydride (MNBA)-mediated dehydration condensation reaction was effectively employed for the formation of the 16-membered macrocyclic depsipeptide moiety of FE399. FE399 was found to exist as an inseparable equilibrium mixture of conformational isomers; the mixture was quantitatively transformed into the corresponding S-benzyl product and isolated as a single isomer. Thus, we could confirm that the molecular structure of FE399 obtained by this method is identical to that of the natural product.</div>

Total Synthesis of the Antitumor Depsipeptide FE399 and its S-Benzyl Derivative: A Macrolactamization Approach

2020 ◽  
Author(s):  
Takayuki Tonoi ◽  
Miyuki Ikeda ◽  
Teruyuki Sato ◽  
Takehiko Inohana ◽  
Ryo Kawahara ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Total Synthesis ◽  
Natural Product ◽  
Condensation Reaction ◽  
Practical Method ◽  
Equilibrium Mixture ◽  
Conformational Isomers ◽  
Single Isomer

<div>An efficient and practical method for the synthesis of (9R,14R,17R)-FE399, a novel antitumor bicyclic depsipeptide, was developed. A 2-methyl-6-nitrobenzoic anhydride (MNBA)-mediated dehydration condensation reaction was effectively employed for the formation of the 16-membered macrocyclic depsipeptide moiety of FE399. FE399 was found to exist as an inseparable equilibrium mixture of conformational isomers; the mixture was quantitatively transformed into the corresponding S-benzyl product and isolated as a single isomer. Thus, we could confirm that the molecular structure of FE399 obtained by this method is identical to that of the natural product.</div>

scholarly journals Probing the structure and electronic properties of beryllium doped boron clusters: A planar BeB16− cluster motif for metallo-borophene

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Dongliang Kang ◽  
Weiguo Sun ◽  
Hongxiao Shi ◽  
Cheng Lu ◽  
Xiaoyu Kuang ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Electronic Properties ◽  
Molecular Orbital ◽  
Strong Interaction ◽  
Chemical Bonding ◽  
Relative Stability ◽  
Low Energy ◽  
Nano Materials ◽  
Boron Clusters ◽  
Bonding Analysis

Abstract Beryllium-doped boron clusters display essential similarities to borophene (boron sheet) with a molecular structure characterized by remarkable properties, such as anisotropy, metallicity and high conductivity. Here we have determined low-energy structures of BeBn0/− (n = 10–20) clusters by utilizing CALYPSO searching program and DFT optimization. The results indicated that most ground states of clusters prefer plane or quasi-plane structures by doped Be atom. A novel unexpected fascinating planar BeB16− cluster with C2v symmetry is uncovered which possesses robust relative stability. Furthermore, planar BeB16− offers a possibility to construct metallo-borophene nano-materials. Molecular orbital and chemical bonding analysis reveal the peculiarities of BeB16− cluster brings forth the aromaticity and the strong interaction of B-B σ-bonds in boron network.

Molecular Structure of the Outermost Cell Wall Component of Spirillum Serpens

1977 ◽  
Vol 35 ◽  
pp. 342-343
Author(s):  
Wah Chiu ◽  
David Grano
Keyword(s):  
Molecular Structure ◽  
Cell Wall ◽  
Outer Membrane ◽  
Gel Electrophoresis ◽  
Electron Microscopic Examination ◽  
Electron Microscopic ◽  
Cell Wall Component ◽  
Protein Components ◽  
Exposure Technique ◽  
Structural Aspects

The periodic structure external to the outer membrane of Spirillum serpens VHA has been isolated by similar procedures to those used by Buckmire and Murray (1). From SDS gel electrophoresis, we have found that the isolated fragments contain several protein components, and that the crystalline structure is composed of a glycoprotein component with a molecular weight of ∽ 140,000 daltons (2). Under an electron microscopic examination, we have visualized the hexagonally-packed glycoprotein subunits, as well as the bilayer profile of the outer membrane. In this paper, we will discuss some structural aspects of the crystalline glycoproteins, based on computer-reconstructed images of the external cell wall fragments.The specimens were prepared for electron microscopy in two ways: negatively stained with 1% PTA, and maintained in a frozen-hydrated state (3). The micrographs were taken with a JEM-100B electron microscope with a field emission gun. The minimum exposure technique was essential for imaging the frozen- hydrated specimens.

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