228
N. Tshilande and L. Mammino
greater differences appear only for some conformers with higher energy. The values
of the O ˆ
HO bond angles of the first IHB are the same for MODL and the three
molecules. The distance between the donor H atom and the closest C atom in the
acceptor aromatic B ring for the O–H···π IHBs (Table S85; Fig. S78) is the same for
corresponding conformers of MODL and the three molecules.
The values of the dipole moment are always very close for corresponding conformers of MODL, c-DBPO and t-DBPO (Table S86; Fig. S79), whereas the values
for MYRA are slightly (0.04–0.172 D) smaller than those of MODL for the conformers with relative energy lower than 4.86 kcal/mol, and can be more significantly
smaller or greater (by up to 4.86 D difference) for some higher energy conformers.
This confirms that the dipole moments of the conformers are majorly influenced by
the orientation of the OHs and other features of the ABDE ring system, and only
marginally by the R chain.
The HOMO-LUMO energy gaps (Table S86, Fig. S80) are very close for the conformers with relative energy lower than 4.86 kcal/mol; minor discrepancies appear for
conformers with somewhat greater relative energies and more considerable discrepancies for conformers with considerably higher relative energy. Figure S15 compares
the shapes of the HOMO and LUMO for corresponding conformers of MODL and
the three molecules, highlighting extensive correspondence in the orbital shape and
electron density distribution.
Overall, these comparisons show that MODL is a good model for the three
molecules, above all for the conformers with relative energies lower than 5 kcal/mol,
which includes all the conformers that might be involved in the biological activity.
As already mentioned, comparisons of the properties of corresponding conformers
having different geometries of R and the same geometry of ABDE can be carried
out only for the three molecules, because no such conformers exist for MODL.
Furthermore, comparisons can concern only rotations around the bonds numbered
as 1–8, because no rotation is possible for c-DBPO and t-DBPO around the bond
numbered as 9, as it is a double bond. Since HF, DFT and MP2 results are available
for these conformers, the values of each property are compared individually for
each calculation method. The relative energies (Tables S88, S89; Figs. S81, S82)
are mostly very close for corresponding conformers in the HF and DFT results.
For HF results, some discrepancies appear for d-r-η-p-a-e-j-2y and d-r-η-p-a-e-j2z (where the relative energy is higher for c-DBPO and t-DBPO than for MYRA)
and for d-r-η-p-a-e-j-3y, d-r-η-p-a-e-j-8y and d-r-η-p-a-e-j-8z (where the relative
energy is smaller for c-DBPO and t-DBPO than for MYRA). For DFT results, some
discrepancies appear only for d-r-η-p-a-e-j-3y, d-r-η-p-a-e-j-8y and d-r-η-p-a-e-j-8z.
The MP2 results (Table S90, Fig. S83) show greater differences between the energies
of corresponding conformers, including corresponding conformers of c-DBPO and
t-DBPO.
The length of the H15···O14 first IHB (Tables S91–S93; Figs. S84–S86) has mostly
close values for corresponding conformers. The greatest discrepancy concerns d-r-ηp-a-e-j-2y and d-r-η-p-a-e-j-2z, where the length for c-DBPO and t-DBPO is shorter
than for MYRA, in the results of all the three calculation methods. The lengths for
N. Tshilande and L. Mammino
greater differences appear only for some conformers with higher energy. The values
of the O ˆ
HO bond angles of the first IHB are the same for MODL and the three
molecules. The distance between the donor H atom and the closest C atom in the
acceptor aromatic B ring for the O–H···π IHBs (Table S85; Fig. S78) is the same for
corresponding conformers of MODL and the three molecules.
The values of the dipole moment are always very close for corresponding conformers of MODL, c-DBPO and t-DBPO (Table S86; Fig. S79), whereas the values
for MYRA are slightly (0.04–0.172 D) smaller than those of MODL for the conformers with relative energy lower than 4.86 kcal/mol, and can be more significantly
smaller or greater (by up to 4.86 D difference) for some higher energy conformers.
This confirms that the dipole moments of the conformers are majorly influenced by
the orientation of the OHs and other features of the ABDE ring system, and only
marginally by the R chain.
The HOMO-LUMO energy gaps (Table S86, Fig. S80) are very close for the conformers with relative energy lower than 4.86 kcal/mol; minor discrepancies appear for
conformers with somewhat greater relative energies and more considerable discrepancies for conformers with considerably higher relative energy. Figure S15 compares
the shapes of the HOMO and LUMO for corresponding conformers of MODL and
the three molecules, highlighting extensive correspondence in the orbital shape and
electron density distribution.
Overall, these comparisons show that MODL is a good model for the three
molecules, above all for the conformers with relative energies lower than 5 kcal/mol,
which includes all the conformers that might be involved in the biological activity.
As already mentioned, comparisons of the properties of corresponding conformers
having different geometries of R and the same geometry of ABDE can be carried
out only for the three molecules, because no such conformers exist for MODL.
Furthermore, comparisons can concern only rotations around the bonds numbered
as 1–8, because no rotation is possible for c-DBPO and t-DBPO around the bond
numbered as 9, as it is a double bond. Since HF, DFT and MP2 results are available
for these conformers, the values of each property are compared individually for
each calculation method. The relative energies (Tables S88, S89; Figs. S81, S82)
are mostly very close for corresponding conformers in the HF and DFT results.
For HF results, some discrepancies appear for d-r-η-p-a-e-j-2y and d-r-η-p-a-e-j2z (where the relative energy is higher for c-DBPO and t-DBPO than for MYRA)
and for d-r-η-p-a-e-j-3y, d-r-η-p-a-e-j-8y and d-r-η-p-a-e-j-8z (where the relative
energy is smaller for c-DBPO and t-DBPO than for MYRA). For DFT results, some
discrepancies appear only for d-r-η-p-a-e-j-3y, d-r-η-p-a-e-j-8y and d-r-η-p-a-e-j-8z.
The MP2 results (Table S90, Fig. S83) show greater differences between the energies
of corresponding conformers, including corresponding conformers of c-DBPO and
t-DBPO.
The length of the H15···O14 first IHB (Tables S91–S93; Figs. S84–S86) has mostly
close values for corresponding conformers. The greatest discrepancy concerns d-r-ηp-a-e-j-2y and d-r-η-p-a-e-j-2z, where the length for c-DBPO and t-DBPO is shorter
than for MYRA, in the results of all the three calculation methods. The lengths for