Stereoselective synthesis of chiral piperidine derivatives employing arabinopyranosylamine as the carbohydrate auxiliary
Bibliographic record
Abstract
Stereoselective synthesis of 2-substituted dehydropiperidinones and their further transformation to variously disubstituted piperidine derivatives was achieved employing D-arabinopyranosylamine as the stereodifferentiating carbohydrate auxiliary. A domino MannichMichael reaction of 1-methoxy-3-(trimethylsiloxy)butadiene (Danishefsky's diene) with O-pivaloylated arbinosylaldimines furnished N-arabinosyl dehydropiperidinones in high diastereoselectivity. Subsequent conjugate cuprate addition gave 2,6-cis-substituted piperidinones, while enolate alkylation furnished 2,3-trans-substituted dehydropiperidinones. Electrophilic substitution at the enamine structure afforded 5-nitro- and 5-halogen dehydropiperidinones of which the latter were applied in palladium-catalyzed coupling reactions. The absolute configuration of the obtained products was proven by NMR and X-ray structure analysis as well as by syntheses of the alkaloids (+)-coniine and (+)-dihydropinidine.Key words: piperidine alkaloids, carbohydrate auxiliary, domino MannichMichael reaction, conjugate cuprate and hydride addition, electrophilic substitution of enamines.
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How this classification was reachedexpand
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) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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 teacher head, 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".