Formation of <i>N</i><sup>α</sup>-terminal 2-dialkyl amino oxazoles from guanidinated derivatives under mild conditions
Bibliographic record
Abstract
Oxazole-containing peptides are an important class of molecules in medicinal chemistry programs. Here we describe a convenient solid-phase synthesis of Nα-terminal oxazole peptides. The strategy took advantage of an intramolecular rearrangement side reaction that occurred during the guanidination of the Nα-amino function of a peptide still anchored on the solid-support. The substitution map of the N,N-dialkylamino oxazole obtained using this strategy differed completely from the one achieved through the heterocyclization of the Ser or Thr side chain with the preceding carbonyl group, which is a common approach for the preparation of these compounds. This unexpected reaction was observed with N-terminal aromatic and aliphatic amino acids that have a Gly as the last before residue in both short as well as long peptides; however, it does not form the oxazole ring if Gly was substituted with other amino acids.
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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 | 0.000 |
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 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".