KfâSffiBEBEftE^EftK SYNTHESIS
METATHESIS MAGIC Polymer-bound chiral catalyst makes optically pure compounds
T
RADITIONALLY TRICKY, THE
formation of carbon-carbon bonds is a muchsought-after goal of the compound-creating organic chemist. One extremely important synthetic route to this atomic marriage is olefin metathesis, in which two molecules—each with carbon-carbon double bonds— exchange carbons, bringing along any attached groups. The process, used to make everything from polymers to pharmaceutical^ important compounds, is usually accomplished with the help of an organometallic catalyst. Now comes the first catalyst for this reaction that's not only supported and recyclable, but also chiral [Angew. Chem. Int. Ed., 41,589 (2002)}. It was developed
by chemistry professors Richard R. Schrock at Massachusetts Institute of Technology and Amir H. Hoveyda at Boston College and their postdoctorol fellow Kai C. Hultszch and graduate student Jesper A. Jernelius. The fact that the molybdenum-based catalyst is supported—that is, sits in a layer on a chunk of some material, in this case a polymer—is important because it can be easily removed after the reaction. That means fewer impurities left behind, a problem that plagues reactions performed with homogeneous catalysts. The catalyst can also be reused several times. These properties make the catalyst attractive for use in combinatorial chemistry Hoveyda says.
SCIENCE
DIAGNOSING OVARIAN CANCER Proteomics shows promise for early detection of deadly disease
A
NEW PROTEOMIC
TEST
could help improve the survival rates for ovarian cancer by making it easier to diagnose the disease in its early stages. Ovarian cancer is usually detected at a late stage and consequently has a low five-year survival rate. A team of scientists and physicians from the Food & Drug Administration, the National Cancer Institute, the Bethesda, Md.-based bioinformatics company Correlogic Systems, and other organizations combined HTTP://PUBS.ACS.ORG/CEN
mass spectrometry and bioinformatics to identify proteomic patterns in blood samples that are indicative of ovarian cancer
{Lancet, 359,572 (2002)}. The protein signatures were generated by comparing mass spectra of blood serum samples from 50 women with ovarian cancer and 50 women without ovarian cancer. T h e patterns were then used to classify another 116 samples. Of those, all 50 cases of cancer—including 32 in stage I— were correctly diagnosed. Of the 66 noncancerous samples, 63
That the catalyst is chiral is even more important: It allows the chemists to make products that are highly enantiomerically selective. A number of optically pure compounds that are difficult to come by could be made with the catalyst, the authors say T h e group tested the catalyst in a number of asymmetric reactions, which they say were efR = ferf-butyl, R' = isopropyl ficient and proMO BETTER New Mo-based duced enantiocatalyst is supported and selective products recyclable, and it produces in high yields. enantioselective products. The catalyst, in which a chiral ligand is attached to the polymer by a rigid tether, is based on a family of achiral catalysts developed in Schrock's lab. The two groups developed the chiral version with the help of "modeling and intuition," Hoveyda says-ELIZABETH WILSON
were correctly classified. The positive predictive value (a measure of the reliability of the test) was 94% for the proteomic test, compared with 35% for the same samples using a common biomarker for ovarian cancer. "We think this [predictive value] may improve with more training of the artificial intelligence tool," says lead author Emanuel F. Petricoin III, codirector of the FDA-NCI Clinical Proteomics Program, "but it will be challenging to maintain 100% sensitivity and 95% specificity" The next step is to use the test with larger groups ofpatients. The test will probably not be used alone. "We feel that no single test, even one that looks at millions of combinations of serum proteins, should be used as a stand-alone and that the more information the physician has at his disposal, the better," Petricoin says.—CELIA HENRY
C&EN
IW-BJHBEi îCjyâHÉflrÇATI
Now two months old, "Cc:" is the first and only one of 87 implanted cloned cat embryos to survive, say researchers at Texas A&M University [Nature Online, http://www. nature.com/nsu/ 020211/020211-13. html). She is completely unlike her surrogate mother but is a genetic match to her donor mother. / FEBRUARY
18, 2002
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