Science Concentrates NATURAL PRODUCTS
▸ Chameleoninspired elastomer Trying to mimic chameleon skin with a synthetic material presents scientists with a twofold challenge: The material must change color and must possess skin’s ability to go rapidly from a soft, compliant state to a stiff one that prevents tearing. Scientists led by Sergei S. Sheiko of the University of North Carolina, Chapel Hill, and Andrey V. Dobrynin of the University of Akron managed to marry these two features— color shifting and stiffening upon strain— into a moldable Researchers molded elastomer made this chameleon-like from polymers elastomer into a butterfly with a 2-cm with brushlike architecture wingspan. Edges (Science 2018, were swollen with polydimethylsiloxane DOI: 10.1126/ to make them appear science.aar5308). turquoise. The polymer has linear ends and a central region that resembles a bottle brush, in which polydimethylsiloxane chains extend like bristles from a linear polymer backbone. These polymers form a physically cross-linked network that is soft but, like skin, stiffens upon deformation. The network also scatters light of different hues, from turquoise to a vibrant blue, depending on the stretched state of the elastomer. For now, the stiffness and color change are coupled, but the researchers note they would like to create a material in which these features can be controlled independently.—BETHANY
HALFORD
SYNTHESIS
▸ Powerful acid persuades reluctant alkenes to react To drive reactions forward, catalytic Brønsted acids wield protons to provoke molecular bonds into action. These organic catalysts have acted on oblig-
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C&EN | CEN.ACS.ORG | APRIL 2, 2018
Potent insecticidal peptide found in worms Researchers have found, in the world’s longest animal, one of the most potent insecticidal peptides ever discovered (Sci. Rep. 2018, DOI: 10.1038/ s41598-018-22305-w). From the sea bottom off the western coast of Sweden, Ulf Göransson of Uppsala University and coworkers collected bootlace worms, Lineus longissimus, which are up to 50 meters long. When poked, the worms released mucus that contained three novel peptides. The researchers sequenced one of these, which they called nemertide -1, and made more of it by chemical peptide synthesis to obtain a sufficient amount to study. Nemertide -1’s solution Adult bootlace NMR structure showed that it folds around an inhibworms can grow itor cystine knot, a peptide motif containing three diup to 50 meters long. sulfide bridges. Tiny amounts injected into crabs and cockroaches paralyze and kill the organisms. Nemertide -1 works by slowing the inactivation of sodium channels in nerve cells, forcing the channels into a constant “on” state that causes initial hyperactivity and then low muscle tone and subsequent paralysis. But it works 100 times better on insect sodium channels than it does on mouse and human sodium channels. The compound’s high insect-killing potency and selectivity points to the “potential use of -nemertides in the development of novel insecticides,” the researchers say.—STU BORMAN
Institute for Kohlenforschung have now breached this barrier in reaction scope for Brønsted acids using a highly acidic, chiral imidodiphosphorimidate (IDPi) compound (Science 2018, DOI: 10.1126/ science.aaq0445). The researchers propose that the substrates—1,1-disubstituted alkenes with pendant alO R2 R2 cohols—squeeze into an IDPi catalyst R1 ( ) OH 60 °C, 1–7 days enzymelike pocket in the 2 ) ( 1 R n n R catalyst. The stereode2 R fined cavity facilitates a R1 = Alkyl, aryl, vinyl R2 = H, methyl ring-forming reaction to n = 1, 2 give tetrahydrofuran and tetrahydropyran products in high enantioselectivity. Ar Ar Ar = The team additionally reveals one example of an O O intermolecular version of O O P N P the reaction, albeit with O O NH S CF3 N slightly lower yield and R= selectivity than its tethR Ar Ar R ered counterpart. This CF3 IDPi catalyst transformation could be the first of many such alkene hydrofunctionalUsing IDPi’s highly acidic and confining nature, izations, List says.—TIEN researchers were able to perform hydroalkoxylation ing, heteroatom-containing bonds in a variety of transformations, but they’ve been unable to tempt simple, unactivated alkenes—a class of substrates that has been dominated by efficient transition-metal catalysis. Researchers led by Benjamin List at the Max Planck
reactions with challenging unactivated alkenes.
NGUYEN
C R E D I T: BRUN O C. V E LLU T IN I ( B O OT LAC E WO R M) ; SC I EN C E ( BU T T ER F LY)
POLYMERS
