---

name: lucy-ng:dereplicate description: Dereplication only - match observed 13C shifts against reference databases to identify known compounds. Use for quick checks if a compound is already known before deciding whether full CASE is needed.

lucy-ng:dereplicate

Dereplication only - match observed 13C shifts against reference databases to identify known compounds.

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Purpose

This skill performs ONLY dereplication (database matching). It does NOT proceed to full structure elucidation. Use this when you want to:

• Quickly check if a compound is already known
• Identify a natural product from a database
• Get candidate matches before deciding whether full CASE is needed

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Prerequisites

Copylucy --version || pip install lucy-ng

Database: lucy-ng-derep.db

The SQLite compound database lucy-ng-derep.db contains 928K compounds:

• COCONUT: 895,099 natural products with predicted 13C shifts
• NMRShiftDB: 33,344 compounds with experimental 13C shifts
• 111,493 unique molecular formulas indexed for fast lookup

The CLI automatically discovers the database by searching:

1. LUCY_DATABASE environment variable
2. data/reference/lucy-ng-derep.db (project location)
3. Common paths (~/.lucy/, ~/lucy-ng/, ~/.local/share/lucy-ng/)
4. macOS Spotlight (mdfind) for fast discovery

If not found, download with:

Copylucy database download

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Workflow

Step 1: Identify Available Data

Check what NMR experiments are available:

Copy# List experiments and identify 13C spectrum
for dir in */; do
    if [ -f "$dir/acqus" ]; then
        nuc=$(grep "##\$NUC1=" "$dir/acqus" | head -1)
        echo "Experiment $dir: $nuc"
    fi
done

Dereplication requires:

• 13C spectrum (essential) - either binary data or peak list
• Molecular formula (essential) - from user (simulating HRMS)

Step 2: Request Molecular Formula

Always ask the user for the molecular formula. Do not extract from metadata.

Copy"Please provide the molecular formula for this compound (typically from HRMS)."

Step 3: Run Dereplication

From Bruker spectrum (preferred)

Copylucy dereplicate c13 <bruker_13c_path> <formula> -n 10

The CLI automatically discovers and uses lucy-ng-derep.db.

From peak list (Python API)

Copyfrom lucy_ng.database import DatabaseQueryService
from lucy_ng.dereplication import DereplicationService

shifts = [187.81, 152.55, 135.73, 123.41, 120.68, 120.09, 118.99, 113.45]

# db_path auto-discovered or specify explicitly
with DatabaseQueryService(db_path) as query:
    service = DereplicationService(query)
    result = service.dereplicate_from_shifts(shifts, "C16H10N2O2", top_n=10)

    for match in result.top_matches:
        print(f"{match.entry.name}: score={match.score:.3f}")

Step 4: Interpret Results

Step 5: Report Results

For strong/possible matches:

Copy## Dereplication Results

**Molecular Formula:** C16H10N2O2
**Database:** lucy-ng-derep.db (928K compounds)

### Top Matches

| Rank | Compound | Score | Avg Deviation |
|------|----------|-------|---------------|
| 1 | [Name] | 0.XX | X.X ppm |
| 2 | [Name] | 0.XX | X.X ppm |

### Assessment

[Strong/Possible/Weak/No] match found.

**Top candidate:** [Name]
**Confidence:** [High/Medium/Low]
**SMILES:** [if available]

### Recommendation

[Either "Compound likely identified as X" or "Consider full CASE for confirmation"]

For no matches:

Copy## Dereplication Results

**Molecular Formula:** C16H10N2O2
**Database:** lucy-ng-derep.db (928K compounds)

No strong matches found (best score: 0.XX)

This suggests:
1. Novel compound not in database
2. Known compound with different stereochemistry
3. Compound not yet added to reference database

### Recommendation

Proceed to full CASE: `/lucy-ng:CASE`

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Important Notes

1. This skill does NOT perform full structure elucidation
2. Molecular formula must come from user, not metadata
3. Symmetry affects matching - if formula has 16 carbons but only 8 signals, the compound has symmetry
4. Database is ~100x faster than SD file scanning due to formula-based indexing

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Quick Reference

Copy# Quick dereplication with CLI (auto-discovers database)
lucy dereplicate c13 ./2 C16H10N2O2 -n 10

# Check database status
lucy database info lucy-ng-derep.db

# Download database if missing
lucy database download