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Configurational and Conformational Analysis of 5-deoxy-5-iodo-α,β-D-ribose with 3-Sphere Approach
Carmen-Irena Mitan,
Emeric Bartha,
Anca Hirtopeanu,
Carmen Stavarache,
Constantin Draghici,
Miron Teodor Caproiu,
Maria Maganu,
Petru Filip
Issue:
Volume 7, Issue 1, June 2023
Pages:
1-8
Received:
7 March 2023
Accepted:
27 March 2023
Published:
11 April 2023
Abstract: Configurational and conformational analysis with 3-Sphere approach on selective iodination of α, β-methyl D-ribofuranose (2-α:2-β) with iodotriphenilphosphonium iodide complex [Ph3P+I]I- generated in situ, under RT, reflux, microwave and sonochemistry. Introduction of the unit and hypersphere trigonometric equations, under Hopf fibration and Lie algebra theories, on Lambert-Wu methods enable calculation of the dihedral angles from NMR data (13C chemical shift, vicinal coupling constant 3JHH[Hz]) and the ratio of anomers. The conformation/configuration at anomeric position is cis: trans with axial:axial 3-α:3-β (3JH1H2 3 or 4.5:0[Hz]) or equatorial:axial 3-α:3-β (3JH1H2 6 or 4.5:0[Hz]) as state based on dihedral angles θH1H2[deg], recorded carbon chemical shift δCn[deg] and VISION molecular models. The conformation of 3-β anomer is 3E, and in case of 3-α anomer 3E on Altona’s map, the last having the succession of sign (+, -, -) with θH3H4α trans-ee, or alternatively 32T conformation having the succession of sign (-, +, -) with θH3H4α trans-aa. An equilibrium between 3E α and 32T α was confirmed by 3JH1H2 of 4.5[Hz], i.e. negative θH1H2α with 32T and equatorial OCH3, or positive θH1H2α with 3E and axial OCH3. The APT experiment (attached proton test) demonstrated the formation of tetrahydro 2H-pyran-2-ol as side product after selective iodination of methyl 5-deoxy-β-D-ribofuranoside 2-β.
Abstract: Configurational and conformational analysis with 3-Sphere approach on selective iodination of α, β-methyl D-ribofuranose (2-α:2-β) with iodotriphenilphosphonium iodide complex [Ph3P+I]I- generated in situ, under RT, reflux, microwave and sonochemistry. Introduction of the unit and hypersphere trigonometric equations, under Hopf fibration and Lie al...
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3-Sphere Torsional Angles and Six Membered Ring Conformation
Emerich Bartha,
Carmen-Irena Mitan,
Petru Filip
Issue:
Volume 7, Issue 1, June 2023
Pages:
9-15
Received:
16 March 2023
Accepted:
4 April 2023
Published:
24 April 2023
Abstract: The conformation of six membered ring, 1,3,4-tri-o-acetyl-2-azido-6-bromo-2,6-dideoxy-D-galactose α-1 and β-1, and 2,6-dideoxy-2,6-imino- D-talonic acid 2D and L-talonic acid 2L, is analyzed inscribing two five membered ring on six membered ring. Altona’s five membered ring conformational parameters, phase angles of the pseudorotation P1, P2 [deg] and angle of deviation from planarity θm [deg] = f(P [deg]), are calculated with Java Script program using 3-Sphere torsional angles. The correlation between Altona map and six membered ring Stoddart’s diagram conformations was confirmed with VISION molecular models. 3-Sphere torsional angles θnn+1 [deg] for all cis, trans-ee, -aa stereochemistry are disclosed from trigonometric point of view, Hopf fibration confirmed by Lie algebra. The cis, trans stereochemistry on two units with six sets angles ensure relationships between dihedral θHnHn+1 [deg]/vicinal angles ϕ [deg] (θBn + A = θAn, θAn = θHnHn+1, θBn = ϕ), and between dihedral θHnHn+1 [deg]/torsional angles θnn+1 [deg] (θnn+1 = A +/- θHnHn+1); in first case A = 150 for trans-aa6,1 and A = 90 for trans-aa5,2 and trans-ee stereochemistry, in last case A = 180 [deg] for cis and trans-aa stereochemistry and A = 120 [deg] for trans-ee stereochemistry. The number of dihedral angles with positive and negative sign results from 3-sphere approach for only one vicinal coupling constant 3JHnHn+1 [Hz] are restricted by the VISION molecular models.
Abstract: The conformation of six membered ring, 1,3,4-tri-o-acetyl-2-azido-6-bromo-2,6-dideoxy-D-galactose α-1 and β-1, and 2,6-dideoxy-2,6-imino- D-talonic acid 2D and L-talonic acid 2L, is analyzed inscribing two five membered ring on six membered ring. Altona’s five membered ring conformational parameters, phase angles of the pseudorotation P1, P2 [deg] ...
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The Geometry, Electronic Structure and Response Properties of Trans Polyacetylene, a First Principle Study
Issue:
Volume 7, Issue 1, June 2023
Pages:
16-19
Received:
28 March 2023
Accepted:
12 April 2023
Published:
27 April 2023
Abstract: Polyacetylene, as the simplest and the most typical conjugated polymer system with great potentials in electronics industry, was intensively studied both experimentally and theoretically in the recent decades. Many important issues about polyacetylene have been made clear, but there are still some important questions to be answered by further study. Quantum chemists often choose to extrapolate the oligomer properties to obtain the polymer properties, while the solid state physicists prefer to start with periodic boundary condition. In this article, the geometry, electronic structure and polarizability and the second hyper-polarizability of trans polyacetylene chain were studied with first principles calculations. Several commonly used functionals and basis sets were used in the study. Comparing with experimental results, the chemical model CAMB3LYP with 6-311G(d,p) basis set presents a good description for geometry, electronic structure and polarizabilities of trans polyacetylene. Response of trans polyacetylene to a longitudinal electrostatic field along the chain were obtained within the finite field scheme, and the polarizability and second hyper-polarizability were compared with those extrapolated from oligomers. It was found that the polarizability and the second hyper-polarizability of trans polyacetylene are much larger than those obtained through quadratic extrapolation from oligomer polyenes, as shows the computational study starting from periodic boundary conditions is essentially important.
Abstract: Polyacetylene, as the simplest and the most typical conjugated polymer system with great potentials in electronics industry, was intensively studied both experimentally and theoretically in the recent decades. Many important issues about polyacetylene have been made clear, but there are still some important questions to be answered by further study...
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