Stereoselective Glycosylations Using (<i>R</i>)‐ or (<i>S</i>)‐(Ethoxycarbonyl)benzyl Chiral Auxiliaries at C‐2 of Glycopyranosyl Donors
Why this work is in the frame
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Bibliographic record
Abstract
Abstract The stereoselective introduction of a glycosidic bond presents the greatest challenge to complex oligosaccharide synthesis. Important developments such as automated polymer‐supported oligosaccharide synthesis will not realize their full potential until this problem is addressed. In this paper, a novel approach for stereoselective glycosylations is described whereby a chiral auxiliary at C‐2 of a glycosyl donor controls the anomeric outcome of a glycosylation. It was found that participation of an ( S )‐ethoxycarbonylbenzyl auxiliary led to the formation of 1,2‐ cis glycosides, probably through a trans ‐fused dioxolenium ion intermediate. On the other hand, the use of an auxiliary with ( R ) configuration gave 1,2‐ trans glycosides, and this glycosylation proceeds through a cis ‐fused dioxolenium ion intermediate. The auxiliary could conveniently be removed by Birch reduction. Computational studies support the formation of the proposed ethoxy‐carbonium ion intermediate with all pseudo‐equatorial substituents. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
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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 | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.008 | 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 it