Natural Products Chemistry Assignment Help & Online Tutoring

Natural products chemistry is the isolation, purification and structural determination of compounds produced by living organisms, together with their synthesis and their role as drug leads. In practice it combines separation science with spectroscopic structure elucidation and, often, biological assay.

In stages of increasing cost and resolution: extraction from the dried material, solvent partitioning to separate by polarity, column chromatography for bulk separation, then preparative HPLC for final purification. Purity is confirmed by TLC in several systems, analytical HPLC and a clean NMR spectrum.

Partitioning shakes a crude extract between immiscible solvents so compounds distribute according to polarity. A hexane, ethyl acetate, butanol and water series divides a complex extract into broad polarity bands cheaply, which greatly reduces the load placed on later chromatography.

It is isolation directed by biological testing: each fraction is assayed and only active ones are carried forward, so effort concentrates on the compound responsible for the observed effect. Assaying at every stage is essential, since activity can be lost or diluted during fractionation.

Because two or more compounds may have acted together, so separating them destroys the combined effect. Activity can also fall below the assay's detection limit once spread across fractions. Both are reasons to assay every stage and report fraction masses rather than results alone.

Dereplication is the early identification of already-known compounds, using accurate mass, UV data, database searching and the identity of the source organism, so that effort is not spent isolating something already described. Examiners expect to see that it was attempted before novelty is claimed.

For a compound of carbon, hydrogen, nitrogen and oxygen, subtract half the hydrogen count from the carbon count, add half the nitrogen count, then add one. Oxygen does not enter the calculation. The result counts rings and double bonds combined, so a benzene ring contributes four.

IR identifies functional groups from characteristic absorption bands, and band position carries extra information. A broad band near 3200 indicates a hydrogen-bonded hydroxyl, while a carbonyl absorbing lower than normal suggests conjugation with an aromatic ring or a double bond. Band position is therefore evidence, not just identification.

It gives the molecular mass from the molecular ion, and accurate mass measurement can establish the molecular formula directly. Fragmentation patterns indicate which pieces the molecule breaks into, which supports proposed substructures and helps distinguish between isomers that share the same molecular formula and mass.

Proton NMR shows the number, chemical environment and coupling of hydrogen atoms, which reveals neighbouring groups. Carbon NMR shows how many distinct carbons are present and their type. Used together they constrain a structure far more tightly than either does alone.

Two-dimensional experiments establish connectivity. COSY links protons that couple to each other, HSQC links each proton to the carbon bearing it, and HMBC shows longer-range proton to carbon correlations across two or three bonds. HMBC is usually what joins the separate fragments into one complete carbon skeleton.

From the number of aromatic protons and their coupling. Ortho coupling is large, meta coupling small and para coupling very small, so a doublet, a doublet of doublets and a doublet indicate a 1,2,4-trisubstituted ring, while two two-proton doublets indicate para substitution.

Total synthesis builds the target from simple starting materials, proving the structure and advancing methodology but rarely supplying material economically. Semi-synthesis instead modifies a related but more abundant natural compound, which is usually the practical industrial route when a scarce target has an available chemical relative.

Because biosynthesis produces structures unlike those in typical synthetic libraries: larger, more rigid, oxygen-rich and stereochemically complex. Historically they have supplied a large share of drug leads, and interest in them has revived with better dereplication, more sensitive analytical methods and genome-based discovery approaches.

Yes. A one-to-one tutor can work through isolation strategy, degrees of unsaturation and full structure elucidation problems from IR, MS and NMR data with you, and give feedback on your lab report. You complete your own assessed work under your course rules.