Structure Proof and Synthesis of Kotalanol and De-<i>O</i>-sulfonated Kotalanol, Glycosidase Inhibitors Isolated from an Herbal Remedy for the Treatment of Type-2 Diabetes
Bibliographic record
Abstract
Kotalanol and de-O-sulfonated-kotalanol are the most active principles in the aqueous extracts of Salacia reticulata which are traditionally used in India, Sri Lanka, and Thailand for the treatment of diabetes. We report here the exact stereochemical structures of these two compounds by synthesis and comparison of their physical data to those of the corresponding natural compounds. The candidate structures were based on our recent report on the synthesis of analogues and also the structure-activity relationship studies of lower homologues. The initial synthetic strategy relied on the selective nucleophilic attack of p-methoxybenzyl (PMB)-protected 4-thio-D-arabinitol at the least hindered carbon atom of two different, selectively protected 1,3-cyclic sulfates to afford the sulfonium sulfates. The protecting groups consisted of a methylene acetal, in the form of a seven-membered ring, and benzyl ethers. Deprotection of the adducts yielded the sulfonium ions but also resulted in de-O-sulfonation. Comparison of the physical data of the two adducts to those reported for de-O-sulfonated natural kotalanol yielded the elusive structure of kotalanol by inference. The side chain of this compound was determined to be another naturally occurring heptitol, d-perseitol (d-glycero-d-galacto-heptitol) with a sulfonyloxy group at the C-5 position. The synthesis of kotalanol itself was then achieved by coupling PMB-protected 4-thio-d-arabinitol with a cyclic sulfate that was synthesized from the naturally occurring d-perseitol. The work establishes unambiguously the structures of two natural products, namely, kotalanol and de-O-sulfonated kotalanol.
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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) | 0.002 | 0.001 |
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".