Structure determination and synthesis of the mussel toxin azaspiracid
Why was the structure elucidation of azaspiracid-1 such a difficult undertaking? The naturally occurring compound has a very complex skeleton, which consists of nine different, partially fused rings (labeled A to I). Three "figure 8" shaped spirocyclic ring systems (one carbon atom is shared by two rings orientated perpendicular to each other) complicate matters even more, as they allow several possibilities for the 3D structure (configuration) of the molecule. Furthermore, the compound includes 20 stereogenic centers (a stereogenic center is an atom that can be bound to its partner atoms in two possible ways, which are mirror images of each other).
To arrive at the correct structure, the researchers broke up the natural azaspiracid into smaller fragments and also made the corresponding fragments based on the originally proposed structure. They then compared the synthesized fragments with the pieces of the natural puzzle by spectroscopic and chromatographic methods in order to trace the error. This puzzle method allowed them first to verify the structure of the FGHI ring system and then to revise the structure of ring E. A comparison with a related natural product helped further with the ring system ABCD: A double bond had to be shifted one position along from that in the originally proposed structure. The configuration at the two spirocyclic junctions between the rings A, B, and C also had to be revised. The last question, as to which of the mirror images was actually the correct structure of the ABCD ring system, was answered in the final assembly of the pieces of the puzzle into the complete molecule.
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Topic world Synthesis
Chemical synthesis is at the heart of modern chemistry and enables the targeted production of molecules with specific properties. By combining starting materials in defined reaction conditions, chemists can create a wide range of compounds, from simple molecules to complex active ingredients.
Topic world Synthesis
Chemical synthesis is at the heart of modern chemistry and enables the targeted production of molecules with specific properties. By combining starting materials in defined reaction conditions, chemists can create a wide range of compounds, from simple molecules to complex active ingredients.