Synthesis of highly functionalized naphthoate precursors to damavaricin D Observation of kinetically stable benzocyclohexadienones in the bromination reactions of highly functionalized β-naphthol derivatives
Bibliographic record
Abstract
Selective syntheses of the highly substituted bromonaphthoates 4a, 4b, 19, and 22 are reported. These compounds were targeted as precursors to the naphthoquinone nucleus of damavaricin D; compound 22 ultimately was used in the successful total synthesis. The synthesis of 22 features the DielsAlder reaction of the oxygenated diene 5 and 2,6-dibromo-3-methylbenzoquinone 6 to establish the core naphthalenic unit. The quinone was protected throughout this synthesis as a 1,4-bis-methoxymethyl-1,4-dihydroquinone (see 36). The C-2-carboalkoxy group of 22 was added by carboxylation of the aryllithium intermediate generated from 36, and protected as a β-trimethylsilylethyl ester. Finally, the C-8-Br substituent was introduced by NBS bromination of 38. This reaction proceeds by way of bromobenzocyclohexadienone 39. Related bromobenzo-cyclohexadienones 13 and 29 were observed in the NBS brominations of the highly functionalized β-naphthyl MOM ethers 11 and 28. The bromobenzocyclohexadienones 29 and 39 undergo facile substitution reactions with chloride ion and reduction with bromide ion at rates competitive with base-promoted aromatization. The surprising kinetic stability of these intermediates is attributed to a combination of steric and stereoelectronic factors.Key words: damavaricin D, naphthoate precursors, kinetically stable benzocyclohexadienones, aromatic bromination.
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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 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".