A Ketone‐Accepting Pictet–Spenglerase for the Asymmetric Construction of 1,1‐Disubstituted Tetrahydro‐ß‐carboline Alkaloids
Bibliographic record
Abstract
In light of the ubiquity of 1,1'-disubstituted tetrahydro-ß-carboline (THBC) motif in alkaloid natural products, developing asymmetric methodology for its preparation is highly valuable. Despite the immense progress toward achieving stereoselective Pictet-Spengler reaction with aldehydes, the analogous reaction with ketones is still underdeveloped. Exploiting KslB, a Pictet-Spenglerase from the biosynthesis of kitasetaline, we develop a general, diastereoselective, and protecting-group free method for the construction of densely functionalized THBCs with α-quaternary center by coupling tryptophan derivatives and α-keto acids. We determine the stereochemistry of kitasetalic acid, KslB's physiological product and a key biosynthetic intermediate toward kitasetaline, and established that KslB's selectivity is opposite to what is achieved chemically. Our investigations of KslB show its high activity (total turnover number >438000), substrate promiscuity, and tolerance for high substrate concentrations (0.1 M). Additionally, a TrpB-KslB cascade enables the construction of complex tricyclic products from simple indoles in one-pot. X-ray structural characterization of KslB sheds light on potential active site interactions to account for its stereoselectivity and ability to accept ketone substrates.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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) | 0.000 | 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) | 0.000 | 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".