Altona equation

For reasons that have been described in detail,33 it was proposed that Eq. (8) be replaced by a new relationship, now known as the Haasnoot or Altona equation ... 

Secondly, by using the A, B, and C values from Eq. (41), the effect of anomeric configuration was accounted for by fitting the data for the a-furanosides to the full Haasnoot-Altona equation ... 

The Vhh couplings have been used by Abraham and Koniotou to determine the conformer populations of cis- and fr ms-cyclopentane-l,3-diol by the use of the Haasnoot, de Leeuw and Altona equation for the C-CH2-CH2-C fragment the following equation has been derived from five- and six-membered cyclic compounds in fixed conformations ... 

Further improvements of the quahty of the fittings can be achieved by using extended Karplus models that can account for substituent effects. The well-known classical Haasnoot-Altona equation [12] for proton-proton vicinal J-couplings... 

Haasnoot, C. A. G., De Leeuw, F. A. A. M., De Leeuw, H. P. M., Altona, C. Relationship between proton-proton NMR coupling constants and substituent electronegativities. III. Conformational analysis of proline rings in solution using a generalized Karplus equation. Biopolymers 1981, 20,1211-1245. 

Expected J values (Hz) for the Basic Conformations Around Angles for /3- and a-Linked C-Glycosyl Compounds, Deduced by Applying the Generalized Karplus Equation Proposed by Altona to the Geometries Provided by MM3 Molecular-mechanics Calculations ... 

The basic task in the computational portion of MM is to minimize the strain energy of the molecule by altering the atomic positions to optimal geometry. This means minimizing the total nonlinear strain energy represented by the FF equation with respect to the independent variables, which are the Cartesian coordinates of the atoms (Altona and Faber, 1974). The following issues are related to the energy minimization of a molecular structure ... 

When only gauche and anti conformers are significantly populated, their percentages can be estimated using the extended Karplus equation proposed by Altona and coworkers [125] and assuming that gauche and anti minima correspond exactly to 9 = 60° and 9 = 180°, respectively the experimental... 

C. Altona, R. Francke, R. de Haan, J. H. Ippel, G. J. Daalmans, A. J. A. Westra Hoekzema, and J. van Wijk, Empirical group electronegativities for vicinal NMR proton-proton couplings along a C-C bond Solvent effects and reparameterization of the Haasnoot equation, Magn. Reson. Chem., 32 (1994) 670-678. 

E. Dfez, J. San-Fabian, J. Guilleme, C. Altona, and L. A. Donders, Vicinal proton-proton coupling constants. I. Formulation of an equation including interactions between substituents, Molec. Phys., 68 (1989) 49-63. 

P. P. Lankhorst, C. A. G. Haasnoot, C. Erkelens, and C. Altona, Carbon-13 NMR in conformational analysis of nucleic acid fragments. 2. A reparametrization of the Karplus equation for vicinal NMR coupling constants in CCOP and HCOP fragments, J. Biomol. Struct. Dyns., 1 (1984) 1387-1405. 

A large set of hydroquinone derivatives (Fig. 6a) has been studied by Dobado et al. In order to identify regioisomeric compounds, the authors have performed the calculations of chemical shifts and estimation of J(H,H) using the CAL3JHH program, based on Haasnoot-Leeuw-Altona empirical equation. Calculated V(H,H) averaged according to the Boltzmann distribution were compared with the experimental values. 

The inclusion of sine terms was first proposed by Pachler [8] in order to properly take into account the substituent effects upon J(H,H)-couplings in ethyl derivatives. In fact, in his equation, he included an additional sin(20) term to improve the fitting. It was later utilized also by Altona [14,16] and in more recent studies [87,91-97] particularly devoted to carbohydrates. 

C.A.G. Haasnoot, F.A.A.M. de Leeuw, C. Altona, The relationship between proton-proton NMR couphng constants and substituent electronegativities-I. An empirical generalization of the Karplrrs equation. Tetrahedron 36 (1980) 2783. 

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