Biocatalytic Synthesis of α,β-Unsaturated 2-Keto Acids and Derivatives Using the Promiscuous Aldolase, NahE
Bibliographic record
Abstract
Abstract Type I aldolases catalyze carbon–carbon bond-forming reactions to form a diverse set of products in nature but often display high selectivity for their natural substrates. One such aldolase, NahE, is known to catalyze the condensation of pyruvate with a wide range of aldehydes to give trans-4-phenyl-2-oxo-3-butenoic acids under mild aqueous conditions. These α,β-unsaturated 2-oxo acids are versatile intermediates for synthetic transformations. NahE has also been used for the synthesis of α-fluoro-β-hydroxy esters, β-hydroxy esters, and quinaldic acids. However, a thorough study of the substrate scope on a practical scale has not been performed for the native NahE-catalyzed aldol condensation reaction. Here we report that NahE can accept >35 (hetero)aromatic and aliphatic aldehydes. Most condensation products derived from substituted benzaldehydes were isolated in >95% yield without need for further purification, while non-benzaldehyde substrates gave the corresponding products in isolated yields between 26% and 98%. Reactions could be performed on gram scale. These products could be converted into α,β-unsaturated carboxylic acids in up to 93% yield over two steps. This reaction sequence was also performed using whole cells in up to 79% yield. This work demonstrates that NahE is a robust, efficient, and versatile catalyst for organic synthesis.
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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".