Wednesday, March 13, 2013

Let the Sun Shine In

Have you ever wondered why so many chemicals are shipped in amber-tinted bottles? Turns out light can do some pretty sneaky unexpected chemistry.

Reporting in from scenic Switzerland, Gademann & Co recently disclosed a sweet protecting-group free synthesis of Taiwaniaquinol F, a 6-5-6 diterpenoid with "potent cytotoxicity" against certain cancer cell lines. They finish the target in 17 steps, highlighting a Wolff ring-contraction and a neato halogen-oxygen exchange. 

The authors note that the final isolation had to strictly exclude light, or else their product slowly decomposed. Luckily, they asked themselves " what?"

Source: Org. Lett. ASAP | Gademann group
Not to keep you in the dark; their product underwent a spontaneous 1,5 C-H remote functionalization. When the group tried to do it "on purpose" - placing a flask in the sun for 15 minutes - they were rewarded with a 30% yield of cyclized Taiwaniaquinol A.

The authors aren't quite sure what's so special about this system, but note a tantalizing biosynthetic possibility: since Taiwaniaquinol F comes from the bark of a certain tree, and "A" from its leaves, there's a real possibility that this process happens all the time in the plant! No enzymes, no metals, no bases. Just sunshine. 

Nature's amazing.


  1. Photochemical reactions are the best! My being a spectroscopist probably adds some bias to that conclusion, though.