Ab-initio Quantum Mechanical Calculations of NMR Chemical Shifts in Nucleic Acids Constituents III Chemical Shift Variations due to Base Stacking

A total of eight new oxygenated 4-exo-methylene sterols, 1–8, together with one artifact 9 and six known sterols 11–16, were isolated from the marine sponge Theonella swinhoei collected from the Bohol province in Philippines. Structures of sterols 1–8 were determined from 1D and 2D NMR data. Among the sterols, 8α-hydroxytheonellasterol (4) spontaneously underwent an allylic 1,3-hydroxyl shift to produce 15α-hydroxytheonellasterol (9) as an artifact; this was rationalized by quantum mechanical calculations of the transition state. In addition, the 1,2-epoxy alcohol subunit of 8α-hydroxy-14,15-β-epoxytheonellasterol (5) was assigned using the Gauge-Independent Atomic Orbital (GIAO) NMR chemical shift calculations and subsequent DP4+ analysis. Finally, comparison of the 13C chemical shifts of isolated 7α-hydroxytheonellasterol (6) with the reported values revealed significant discrepancies at C-6, C-7, C-8, and C-14, leading to reassignment of the C-7 stereochemistry in the known structure.

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Quantum Mechanical Calculations of Conformationally Relevant1H and13C NMR Chemical Shifts of N-, O-, and S-Substituted Calixarene Systems

Chemistry - A European Journal ◽

10.1002/chem.200700238 ◽

2007 ◽

Vol 13 (25) ◽

pp. 7185-7194 ◽

Cited By ~ 26

Author(s):

Giuseppe Bifulco ◽

Raffaele Riccio ◽

Carmine Gaeta ◽

Placido Neri

Keyword(s):

Chemical Shifts ◽

Quantum Mechanical ◽

Quantum Mechanical Calculations ◽

Nmr Chemical Shifts

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Quantum mechanical calculations on cellulose–water interactions: structures, energetics, vibrational frequencies and NMR chemical shifts for surfaces of Iα and Iβ cellulose

Cellulose ◽

10.1007/s10570-013-0029-x ◽

2013 ◽

Vol 21 (2) ◽

pp. 909-926 ◽

Cited By ~ 20

Author(s):

James D. Kubicki ◽

Heath D. Watts ◽

Zhen Zhao ◽

Linghao Zhong

Keyword(s):

Chemical Shifts ◽

Vibrational Frequencies ◽

Quantum Mechanical ◽

Quantum Mechanical Calculations ◽

Nmr Chemical Shifts

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Quantum mechanical calculations of NMR chemical shifts in nucleic acids

Quarterly Reviews of Biophysics ◽

10.1017/s0033583500004169 ◽

1987 ◽

Vol 20 (3-4) ◽

pp. 113-172 ◽

Cited By ~ 97

Author(s):

C. Giessner-Prettre ◽

B. Pullman

Keyword(s):

Nucleic Acids ◽

Ring Current ◽

Chemical Shifts ◽

Close Relation ◽

Quantum Mechanical ◽

Experimental Measurements ◽

Quantum Mechanical Calculations ◽

Nucleic Acid Bases ◽

Current Effect ◽

Ring Current Effect

During the last twenty-five years the development of quantum mechanical calculations and experimental measurements of chemical shifts of the different type of nuclei present in nucleic acids have run parallel in close relation to each other. The first calculations dealt with intramolecular effects on base proton shifts (Veillard, 1962) but the real breakthrough of the theory occurred with the advent of computations of intermolecular shielding due to the ring current effect of the nucleic acid bases (Giessner-Prettre & Pullman, 1970).

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