Synthesis of Protected 2-Pyrrolylalanine for Peptide Chemistry and Examination of Its Influence on Prolyl Amide Isomer Equilibrium
Bibliographic record
Abstract
Protected enantiopure 2-pyrrolylalanine was synthesized for application in peptide science as an electron-rich arylalanine (histidine) analog with π-donor capability. (2S)-N-(Boc)-N'-(Phenylsulfonyl)-, (2S)-N,N'-bis-(phenylsulfonyl)-, and (2S)-N,N'-bis-(Boc)-3-(2-pyrrolyl)alanines (10, 3, and 14, respectively) were made in 13-17% overall yields and six to seven steps from oxazolidine β-methyl ester 4. Homoallylic ketone 5 was prepared by a copper-catalyzed cascade addition of vinylmagnesium bromide to ester 4 and converted to pyrrolyl amino alcohol 7 by olefin oxidation and Paal-Knorr condensation. Protecting group shuffle and oxidation of the primary alcohol enabled the synthesis of pyrrolylalanines. The bis-Boc analog 14 proved useful in peptide chemistry and was employed to make N-acetyl-pyrrolylalaninyl-proline N''-methylamide 25. A study of the influence of the pyrrole moiety on the prolyl amide isomer equilibrium of 25 using (1)H NMR spectroscopy in chloroform, DMSO, and water demonstrated that the pyrrolylalanine peptide exhibited behavior and conformations different from those of other arylalanine analogs.
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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".