The use of indirectly bonded <sup>13</sup>C‐<sup>1</sup>H (<scp>INCH</scp>) shift correlation spectra for ab initio structure elucidation of natural products and other complex organic compounds; A personal and historical perspective
Why this work is in the frame
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Bibliographic record
Abstract
Abstract This article reviews the use of long‐range shift correlation spectra for structure elucidation of natural products and other complex organic compounds from the early 1980's to the present. Much of it is written from the personal viewpoint of someone who has been involved in this area of research since its earliest days. The first section covers the early use of long‐range correlation spectra in the 1980's. The second section covers the development of specialized pulse sequences for this type of acquisition. It begins with three 13 C‐detected sequences, followed by heteronuclear multiple bond correlation ( HMBC ) and some modified versions of HMBC and, finally, longer range correlation sequences based on the heteronuclear single quantum multiple bond correlation sequence. The third section covers various sequences designed to distinguish between 2‐bond and longer range 13 C‐ 1 H correlations. Unfortunately, none of these can make this distinction for non‐protonated carbons. Only the 1,1‐ ADEQUATE sequence can make this distinction but its very low sensitivity limits its usefulness. The next section focuses on ways of avoiding getting incorrect structures of organic compounds, an ongoing problem in natural product research. The last section includes likely short‐term developments and possible long‐term developments in NMR methodology that would be beneficial for small molecule structure elucidation.
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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 | 0.001 |
| 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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 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