Issue Date: February 1, 2011
With help from a manganese complex, chemists have found a route to the sans-sugar form of lomaiviticin, a scarce molecule with intriguing antibiotic and anticancer activity (J. Am. Chem. Soc., DOI: 10.1021/ja200034b). The synthesis should help clarify how lomaiviticin works and evaluate its potential as inspiration for new drugs.
Made by microbes that live on the body of a Fijian sea squirt, lomaiviticin was first discovered by researchers at Wyeth Pharmaceuticals. It is a butterfly-shaped molecule decorated with several sugars and two surprisingly stable diazo groups—nitrogen groups that ordinarily mark a compound as explosive.
Intrigued by this architecture, Yale University's Seth B. Herzon, with postdoctoral fellows Liang Lu and Shivajirao L. Gholap and graduate student Christina M. Woo, came up with an 11-step, enantioselective route to the sugar-free form, or aglycon, of lomaiviticin. They opted to first build the butterfly's identical "wings," which resemble compounds they and other teams have already tackled, and then forge a congested carbon-carbon bond to join them in a dimer. "Because of the complexity of these molecules, trying to make that bond earlier in the route can create more problems than it solves," Herzon explains.
The team built the bond through an oxidative coupling mediated by a manganese complex that minimized competing reactions. "Making this type of dimer is an amazing accomplishment," and the team's route is both creative and efficient, says Boston University organic chemist John A. Porco Jr., whose team is also working in this area. Porco adds that Herzon's team did more than 1,500 experiments before finding reaction conditions that worked, "which really demonstrates their perseverance."
The group has begun to look at how lomaiviticin's structure contributes to its biological properties, Herzon says. "Next, we've got to get the carbohydrates on" to form the full-fledged natural product.
- Chemical & Engineering News
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