Kinetic resolution of esters via metal catalyzed methanolysis reactions
Bibliographic record
Abstract
Some chiral lanthanide complexes of the Schiff base adducts of: a) bis(2-pyridylcarboxaldehyde) and (1R),(2R)-trans-1,2-diaminocyclohexane (Pyr-R,R'-chxn: 3); b) 6-methyl-2-pyridylcarboxaldehyde and (1R),(2R)-trans 1,2-diaminocyclohexane (MePyr-chxn, 4); and c) 2,6-pyridyldicarboxaldehyde and (1R),(2R)-trans-1,2-diaminocyclohexane ((Pyr-R,R'-chxn)(2), 5) have been screened for their utility to promote kinetic resolution via metal catalyzed alcoholyses of the p-nitrophenyl esters of chiral D- and L-Boc-protected glutamine and phenylalanine. Solvents were varied to optimize the kinetic selectivity values, defined as k(2)(L)/k(2)(D) or k(2)(D)/k(2)(L), for the methanolysis and in some cases, ethanolysis of these substrates. At ambient temperature the greatest selectivity was found for the ethanolysis of Boc-Gln-OPNP, catalyzed by 3:Yb(3+):((-)OEt) (k(2)(L)/k(2)(D) = 7.2). The greatest selectivity for Boc-Phe-OPNP is k(2)(D)/k(2)(L) = 3.9 for its methanolysis promoted by 5:La(3+):((-)OMe). A kinetic method is introduced for the determination of both d and l rate constants for catalyzed alcoholysis from a single kinetic experiment. The activation parameters DeltaH(double dagger) and DeltaS(double dagger) were determined for the metal catalyzed methanolysis and ethanolysis of the Boc-Gln-OPNP substrates, and selectivity factors were found to increase at lower temperatures. A low temperature time course for the ethanolysis of racemic Boc-Gln-OPNP catalyzed by 3:Yb(3+):((-)OEt) at -15 degrees C indicated that after 3 hours 60% residual d-enantiomer was observed having an enantiomeric excess of >95% ee. The activation parameters for the ethanolysis of the same substrate catalyzed by (Pyr-R,R'-chxn)(2):La(3+):((-)OEt) predict a k(2)(D)/k(2)(L) = 40.4 at -40 degrees C with a large ee of >99% with approximately 80% of l isomer remaining at that temperature which has been experimentally confirmed.
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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 | 0.000 |
| 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 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".