Synthesis of Cyclobutane Analogue 4: Preparation of Purine and Pyrimidine Carbocyclic Nucleoside Derivatives
Bibliographic record
Abstract
The coupling of 2-bromo-3-benzoyloxycyclobutanone with purine under basic conditions produces two regioisomers consisting of the N-7 and N-9 alkylated products in equal amounts in their racemic forms. The distribution of the isomers is consistent with the charge delocalization between the N-7 and N-9 positions of the purinyl anion. The structural assignments and relative stereochemistry of each regioisomer were based on 1 and 2D NMR techniques. The relative stereochemistry of the C-2 and C-3 substituents in each regioisomer was the trans orientation consistent with steric factors in the coupling step. The N-9 regioisomer was reduced with sodium borohydride to give the all trans cyclobutanol as the major product in a stereoselective manner. The alcohol was debenzoylated with sodium methoxide in a transesterification step to give the nucleoside analogue. The regioisomeric pyrimidine nucleosides were prepared by Vorbrüggen coupling of the 3-hydroxymethylcyclobutanone triflate with either thymine or uracil followed by stereoselective hydride addition. Regiospecificity of the coupling at the N-1 position was observed and stereoselective reduction to the trans-disubstituted cyclobutanol structure assignments was based on NMR data.
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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 | 0.000 | 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) | 0.000 | 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 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".