Theoretical studies of model compounds of lathyrane-type diterpenes
Bibliographic record
Abstract
The conformation of the 11-membered ring of the lathyrane skeleton has been investigated using NMR spectra and theoretical calculations. Some other skeletons, such as jatrophane, jatrapholane, and tigliane, seem to be derived from this framework, and the conformation is important in connection with the configuration of the resultant diterpenes. The conformation of lathyrane is principally defined by the orientation of the two methyl groups; namely, the methyl groups on C1 and C6 directed above or below the ring plane. Theoretical calculations revealed that the predominant conformation is altered depending on the oxygen functional groups on the ring. As far as the bond lengths, bond angles, and dihedral angles are concerned, all calculation methods afforded reasonable results. In contrast, as regards conformational stability, only the ab initio molecular orbital method (RHF/6-31G*) predicted the most stable conformation, consistent with NOE experiments. On the other hand, the stable conformations predicted by the ab initio method (RHF/STO-3G), the semi-empirical molecular orbital method (MOPAC(PM3)), and the molecular mechanics calculations (MM3) did not necessarily agree with the conformers suggested by the NOE experiments.Key words: ab initio MO, semi-empirical MO, molecular mechanics, 11-membered ring conformation, NOE.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".