Table 3.
NMR/NAMFIS and X-ray structure determined conformations of Taxol evaluated energetically by four force fields in the gas phase, two solvation continuum models with the use of scaled ESP atomic charges; Relative energies, kcal/mol.a
| MMFF | AMBER* | MM2* | MM3* | |||||||||
| Gas | CHCl3 | H2O | Gas | CHCl3 | H2O | Gas | CHCl3 | H2O | Gas | CHCl3 | H2O | |
| 1 | 60.0 | 57.8 | 57.5 | 76.0 | 74.8 | 88.5 | 47.8 | 43.2 | 40.1 | 46.3 | 41.9 | 41.9 |
| 2 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| 3 | 66.1 | 62.6 | 61.5 | 81.6 | 80.9 | 86.6 | 39.2 | 29.7 | 25.8 | 33.2 | 30.1 | 30.1 |
| 4 | 22.6 | 18.0 | 24.9 | 21.7 | 21.5 | 24.5 | 24.3 | 15.2 | 21.7 | 28.1 | 16.4 | 16.4 |
| 5 | 36.5 | 31.6 | 35.3 | 33.4 | 30.9 | 37.8 | 33.0 | 28.9 | 28.5 | 32.0 | 27.4 | 27.4 |
| 6b | 23.7 | 23.0 | 28.1 | 20.0 | 24.9 | 27.2 | 30.0 | 22.6 | 24.6 | 28.6 | 22.9 | 22.9 |
| 7b | 50.2 | 49.9 | 60.6 | 38.8 | 44.2 | 53.6 | 72.4 | 63.2 | 72.3 | 81.3 | 68.0 | 68.0 |
a Each structure was optimized with the indicated force field and the accompanying GBSA solvation model. [2b]b Taxol conformations determined in the solid state;15 optimized using AMBER* with all non-terpenoid core dihedral angles frozen; 6 polar; 7 extended.