Yb(OTf)3-Mediated Ring Opening of Functionalized Cyclopentane Epoxides with Aniline: Aspects of Regiochemistry and Stereochemistry
Bibliographic record
Abstract
The ring-opening reaction of cyclopentan-1-ol 2,3-epoxides bearing alkoxy and hydroxyl groups with aniline was studied in the presence of Yb(OTf) 3 in refluxing toluene.The syn-and anti-relationship of the alkoxy group has an influence on the regioselectivity of attack affording aniline adducts at the secondary or tertiary position.The antibiotic pactamycin 1 isolated in 1961 from a fermentation broth of Streptomyces pactum var.pactum, is a unique member of a handful of naturally occurring aminocyclopentitols 2 (Figure 1).It exhibits activity against bacterial and also as a cytotoxic agent against cancer cell lines. 3Among the several functional groups and unusual patterns of substitution is the presence of a 3-acetyl aniline moiety at C-3.A key reaction in our total synthesis of pactamycin 4 was the introduction of a 3-isopropenyl aniline through the highly regioselective ring opening of an epoxide spanning a secondary and a tertiary carbon center mediated by Yb(OTf) 3 (Scheme 1). 5 The same type of reaction allowed us to prepare a number of substituted aniline analogs of de-6-methylsalicylyl pactamycin and to study their biological activities (Figure 1). 6trigued by the exclusive formation of the aniline corresponding to ring opening at the secondary carbon atom as hoped for, we initiated a study of the ring-opening of stereoisomeric model cyclopentan-1-ol 2,3epoxides with aniline in the presence of Yb(OTf) 3 as a Lewis acid. 7‡ Dedicated to Professor Victor Snieckus wishing him the best in chemistry and in life.
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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 | 0.000 |
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".