Synthesis and Conformational Analysis of a Sulfonium-Ion Analogue of the Glycosidase Inhibitor Castanospermine
Bibliographic record
Abstract
The synthesis of a bridgehead sulfonium salt analogue ( 7 ) of the indolizidine alkaloid castanospermine has been achieved by a multistep procedure starting from 5-thio- d -glucopyranose pentaacetate. The compound was intended to test the theory that glycosidase inhibitory activity of the indolizidine alkaloids might be due to electrostatic stabilization of a positively charged species in the enzyme active site and that a sulfonium salt carrying a permanent positive charge might be advantageous. The structure of the bicylic sulfonium salt ( 7 ) [3( R ),4( S ),5( R ),6( S )-3,4,5-trihydroxy- cis- 1-thioniabicyclo[4.3.0]nonane perchlorate] was confirmed by X-ray crystallography. Analysis of the 1 H NMR spectrum of compound 7 indicated that a similar conformation was adopted in solution. This conformational preference, with hydroxyl groups in the more sterically hindered axial orientations, has been attributed to the dominance of stabilizing electrostatic interactions between the oxygen atoms and the sulfonium center.
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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".