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SYNTHESIS
ONE-POT ROUTE TO NANOCONTAINER Eighteen molecular units condense to form covalent, hexameric host molecule N A STROKE OF SERENDIPITY,
chemists at Rutgers University have discovered a one-pot reaction in which 18 molecular components react sequentially to form, in high yield, a cavernous, covalent molecule that potentially could encapsulate other, smaller molecules (Angew. Chem. Int. Ed., published online Dec. 30,2005, dx.doi.org/ 10.1002/anie.200504049). Although a couple of covalent "nanocontainer" molecules have been synthesized previously, the new route is operationally far more efficient, and it also is atomefficient. These features could be advantageous in potential applications such as drug delivery, separation science, catalysis, and sensing. Peer reviewers of the paper, authored by Ralf Warmuth and coworkers, have been enthusiastic, calling it "elegant," "very impressive," and "spectacular." "This work will be a cornerstone in the development of covalent nanocontainers," one reviewer writes. Warmuth's nanocontainer is an octahedral structure assembled from six bowl-shaped molecules called cavitands and 12 ethylene1,2-diamine linkers. Each cavitand has four formyl groups on its rim, and these react with the 24 amino groups of the linkers to form 24 imine bonds. This condensation is so efficient, Warmuth explains, because the imine bonds form reversibly, "allowing for error correction and ultimately furnishing the thermodynamically most stable product." Once the condensation is complete, the imine bonds are reduced with sodium borohydride so that the octahedral compound can be WWW.CEN-0NLINE.ORG
isolated in 63% yield and purified. The Rutgers team, which includes Xuejun Liu, Yong Liu, and Gina Li, finds that the solvent is a key factor controlling the shape of the nanocontainer. Chloroform is the best solvent for making the octahedral assembly (a hexamer), and other solvents preferentially lead to formation of the octamer PRESTO C H A N G E - 0 Six cavitands or the tetramer, according to condense with 12 linkers to form an Warmuth. octahedral nanocontainer in high yield. Last year, Darren A. Makeiff and John C. Sherman of the Unilarge enough to encapsulate two or versity of British Columbia, Vanthree buckyballs (C60 molecules). couver, reported a related six-caviThus far, however, he and his cotand molecular vessel that entraps workers haven't demonstrated that seven guest molecules (J. Am. Chem. Soc. 2005,127,12363). That their nanocontainer can trap or synthesis involved four steps. slowly release any guest molecules, such as drugs. Those experiments Warmuth's octahedral nanoare now in progress, Warmuth tells container has an inner cavity of C&EN.—RON DAGANI about 1,700 A 3 , which he says is
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CHEMICALS
Cambrex Shifts Strategy And CEO Leaves
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iting risk and the high cost of acquisitions, contract manufacturer Cambrex says it is abandoning its plan to become a specialty therapeutics company and is instead turning its attention to developing its byproducts business. As a result, John R. Leone will step down as president and CEO. Chairman James A. Mack will take over as acting president and CEO. Leone was brought on in August 2004 to shepherd the move into specialty therapeutics. The first major step came two months later through an agreement with Ortec International to commercialize Orcel, a cell therapy for wound healing. Despite the change in direction, Cambrex says it remains committed to the drug. The company will now focus on expanding its bioproducts unit, which accounts for roughly 31% of sales and is its fastest growing business, says a company official. The unit includes cell biolo-
gy, molecular biology, rapid microbial testing, and cell therapy products. Cambrex will also enlist an investment banker to explore strategic alternatives, which could include shedding assets. Vulnerable assets include the animal feed additives product line, which is produced in Charles City, Iowa, and European production facilities, says Dmitry Silversteyn, senior research analyst at Longbow Research. The firm's biopharmaceuticals business, which accounts for about 10% of sales, has struggled since 2003 after losing the contract to manufacture Transkaryotic Therapies' drug Replagal and could also be at risk. "We find the future of the biopharma unit unclear," says JP Morgan analyst Jeffrey Zekauskas. Silversteyn, however, notes that Cambrex has significantly expanded the number of projects in the biopharma pipeline.—LISA JARVIS
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