Saturday, February 25, 2012

Beetle Brood Balls Breed Polycyclic Puzzle

Tripartilactam: Confounding ChemDraw since 2012.
Natural product isolation chemists find fascinating molecules in wild, unexpected places. Hippo sweat. Deep-sea hydrothermal vents. Horse urine. Even maple syrup refining produces new compounds that chemists hope could be the next wonder drug. But a new paper from Org. Lett. ASAP brings forth a new discovery arena for me: dung beetles. Specifically, the giant balls of, well . . .poop, that they push around, then lay their eggs in.

Dung beetles with brood ball
Korean researchers have isolated tripartilactam from a Streptomyces species living in the beetles' brood ball, which they broke apart, cultured, and fractionated. Although the compound has no real biological activity, look at that structure: an 18-4-8 tricycle! Now, cyclobutanes are found in natural products all the time, from sceptrin to ladderanes, but usually not as a "bow-tie" bringing together two huge macrocycles. These scientists figure that a larger polyunsaturated structure was knit together by bacterial enzymes called polyketide synthases, followed by a light-initiated [2+2] to snap the cyclobutane shut.

Chemistry Note: Did you see that 18-4 trans ring juncture? Normally, that species would be far too strained to exist in anything below an 8-4 system. However, in a ring as large as 18, even with the rigid geometry enforced by the lactam and polyolefin chain, there's still enough wiggle room to accomodate this odd duck.


  1. Your mention of equilenin reminds me of Premarin, one of the silliest drug names I'm aware of. Why's it called that? Because it's from PREgnant MARes' urINe. You couldn't make this up.

  2. I'd like to know what the starter unit is for the polyketide; it looks like either a methyl is removed, it starts formyl-propionyl, or it uses a weird 4-carbon unit (followed by a standard A(acetyl)AP(propionyl)AAAAAPAA sequence).