The Avalanche |
The Reduction |
| The Problem: The bloodthirsty Huns have attacked China in great numbers and wish to...well, it's unclear what they really wish to do, but Disney says they're the enemy so clearly they're evil. |
The Problem: Your chemisty professor shows you an intermediate in a synthesis reaction of Cortistatin A, and tells you, "Explain why this reaction selectively reduces only one of the carbon-carbon double bonds." |
In order to save China, some pretty dramatic measures must be taken to reduce the Huns' numbers. |
This intermediate is almost identical to the structure of Cortistatin A, but there is one extra double bond in the D ring. |
The Complication: There aren't that many Chinese soldiers, and the method of destroying the Huns may wipe out the Chinese army as well.
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The Complication: Many metal catalysts for double bond reduction usually reduce every bond in the molecule, which would not lead to Cortistatin A. However, Raney nickel is very sensitive to sterics, and can only reduce sterically unhindered double bonds.
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The Loophole: Fortunately for Mulan's friends, there's a small ledge that offers them protection form the ferocious avalanche.
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The Loophole: Sterics allow Raney nickel to reduce the appropriate double bond in Cortistatin A, but prevent it from reducing the others.
The methyl group above the indicated double bond prevents Raney Nickel from attacking the bond by above, but nothing hinders its approach from below. This bond is reduced.
 
For the other two double bonds, however, Raney nickel cannot approach from either side of the molecule, because the conformation of the ring (top image) and the conformtion of the oxygen atom (bottom image) protect the double bonds. These two bonds are not reduced.
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The Conclusion: A physical barrier protected both the Chinese army in Mulan and the double bonds in the intermediate, which prevented the very power forces operating against both entities from altering their current state of existence.
This study funded by the Department of Useless Comparisons.
Shi, J.; Shigehisa, H.; Guerrero, C. A.; Shenvi, R. A.; Li, C.-C.; Baran, P. S. Angew. Chem. Int. Ed. (English) 2009, 48, 4328-4331. |
