Total synthesis of ()-xyloketal D and its enantiomer Confirmation of absolute stereochemistry
Why this work is in the frame
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Bibliographic record
Abstract
The total synthesis of ()-xyloketal D and its enantiomer have been achieved by the reaction of an ortho-quinone methide with (4R)- and (4S)-4,5-dihydro-2,4-dimethylfuran via a diastereoselective inverse electron demand DielsAlder reaction. This total synthesis confirmed the absolute stereochemistry of the natural product. The ortho-quinone methide was generated by reaction of an appropriately functionalized Mannich base with methyl iodide. The Mannich base was prepared in one step from 2,4-dihydroxyacetophenone, formaldehyde, and morpholine. The enantiomeric dihydrofurans were prepared from (2R)- and (2S)-2-methylpent-4-ynoic acid via a three-step reaction sequence. These chiral nonracemic synthetic precursors were prepared from the corresponding (R)-phenylglycinol-derived diastereomeric amides of the readily available racemic carboxylic acid. The absolute stereochemistry of these carboxylic acids was firmly established by conversion to a known compound that had been previously prepared from a chiral pool starting material.Key words: xyloketal D, inverse electron demand DielsAlder reaction, ortho-quinone methide, dihydrofuran.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| 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 it