3-Azido-tetrahydrofuran carboxylates as scaffolds for oligomers of beta-amino-THF carboxylic acids
Bibliographic record
Abstract
<p>This thesis describes investigations into the synthesis and secondary structural properties of novel carbohydrate-derived peptidomimetics.</p> <p>The syntheses from diacetone-D-glucose of five diastereomeric 3-azido-tetrahydrofuran carboxylates are described. These highly functionalised β-amino acid equivalents are accessed <em>via</em> the diacetone-3-azido-3-deoxy sugars and 3-azido-3-deoxy-1,4-lactones. An acid-catalysed rearrangement results in the formation of the tetrahydrofuran ring with the protected amine functionality already in place in a position β- to the carboxylate group.</p> <p>Attempts to synthesise "carbopeptoids" <em>via</em> various oligomerisation strategies, including three novel approaches to oligomerisation, are delineated. The first approach attempted involves an iterative addition of a bicyclic lactone, which acts as the activated acid component, to the substrate containing an amine functionality. A new solid-phase oligomerisation strategy, whereby the coupling reagent is tethered to the polystyrene support and the substrates remain in solution, is described. The third attempted novel oligomerisation strategy involves activation by microwave irradiation, in the absence of coupling reagents. The conventional coupling using a carbodiimide coupling reagent proves to be a highly efficient means to access oligomers up to six residues in length, and is utilised for the synthesis of the homooligomers of four diastereomeric carbohydrate-derived β-amino acids.</p> <p>The prospect that the carbopeptoids may emulate the helical conformations reported for closely related 2-aminocyclopentanecarboxylic acid oligomers is investigated. Different methods of spectroscopic analysis of the tetrameric and hexameric oligomers are discussed. Circular dichroism spectroscopy provides a rapid diagnostic tool for the investigation of peptide bond orientations and forms the basis for a postulation on a possible stabilised hydrogen-bonding secondary structural conformation in two tetrameric species. Several nuclear magnetic resonance spectroscopic experiments are performed, enabling the assignment of each signal in the proton spectrum for a hexameric oligomer. However the resulting data does not provide sufficient evidence for a well-defined secondary structural motif, and so the potential conformational preference postulated on the basis of circular dichroism spectroscopy is not confirmed.</p>
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".