Researchers Create Chemical Reagents from Pine Terpenes

Scientists at Rice University have developed efficient aminating and hydroxylating chemical reagents made with terpene compounds derived from pine trees, the Houston-based institution of higher learning announced Monday, potentially offering an eco-friendly, biorenewable and cost-effective reagent for use in fine chemical synthesis.

“Terpenoids like camphor and fenchone are abundant and biorenewable natural products,” said synthetic chemist Lászlo Kürti, who led the research effort at Rice, in a statement. “I’m excited about their use as robust reagent scaffolds because these are about as cheap as they get.”

The research was published this week in an issue of Nature Chemistry. Reagents developed in Kürti’s lab help transfer oxygen and nitrogen atoms during the synthesis of compounds and, unlike most other reagents, can be recycled and reused again. According to Kürti, manufacturers may be able to save money by using the newly discovered terpene-based reagents.

“The Rice researchers sought a better way to incorporate nitrogen and oxygen atoms into sometimes delicate molecules and in the process discovered a single scaffold that could be used for the transfer of either oxygen or nitrogen,” the university’s press release said.

Kürti said that researchers have been thinking about a one-step conversion of negatively charged carbons, like carbanions found in arylmetals, into primary amines that contain a new nitrogen-carbon bond, but faced difficulties because nitrogen-hydrogen bonds in traditional aminating agents are highly acidic and can quickly destroy delicate carbanions.

“We demonstrated that camphor and fenchone-derived bulky nitrogen oxaziridines (triangular molecules in which oxygen, nitrogen, and carbon atoms are interconnected) transfer the nitrogen atom exclusively to arylmetals, while nitrogen-alkyl oxaziridines transfer the oxygen atom exclusively,” said Kürti.

One benefit of the terpene-based reagents is that they are stable at room temperature, according to the university.

“We can keep it on a bench indefinitely and nothing happens to it,” said Kürti. “The previous processes were less practical since they relied on highly reactive – thus unstable – animating agents that required storage at low temperatures.”

Kürti described the discovery as “remarkable,” given the terpene-based reagent’s stability and versatility.

“Oxygen and nitrogen are exceedingly important heteroatoms,” said Kürti. “So using the same biorenewable terpenoid scaffold and making just a very minor structural change to transfer one or the other heteroatom is huge. It’s stable, it doesn’t decompose, it doesn’t use transition metals and you don’t need expensive ligands. That’s why it’s so cool.”

The National Institutes of Health (NIH), The National Science Foundation (NSF), the Robert A. Welch Foundation, Amgen, and Biotage helped support the research.

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