SCIENCE & TECHNOLOGY

H T T P : / / W W W . C E N - O N L I N E . O R G C&EN / APRIL 28. 2003 25

iï> t\ K l Α Γ Μ 111 H Λ 1ΓΤ ΓΤ H

Easy recipe for urea derivatives Add two equivalents of a substituted urea to a mixture of one equivalent of isocyanide and one equivalent of acid chloride in tetrahydrofuran. Stir for six to nine hours at 25 °C. Filter off

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I ° R 1 - N = C: R 1 ^ N ^ C ^ N ^ N / R 3 CI-

1 Κ Κ 0 H R2 R4

2 R^ X /R3

H R* 0 0

o R ^ N ^ N ^

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and wash the salt. That's how easy it is to prepare highly substi­tuted formamidine urea derivatives in yields of 50 to 80% using a condensation reaction invented by Amy S. Ripka, working with M. G. Finn, K. Barry Sharpless, and David D. Diaz at Scripps Re­search Institute [Org. Lett., 5,1531 (2003)}. Formamidine ureas— formed here as hydrochloride salts—are important components of bioactive molecules, but a general synthetic route has been lacking until now The coproduct, an iV-acylurea, is easily isolat­ed by evaporating the solvent from the mother liquor.

Ed., 42,1848 (2003)}. "The ex­istence of two types of chan­nels with very different char­acteristics in the same network offers prospects of the simul­taneous introduction of two different species into different channels: for example, ions of opposite charge, such as F~ in­to the hydrophilic channels and a range of cations into the hy­drophobic channels," the re­searchers write. D-Saccharic acid is the polyhydroxydicar-boxylic acid derived from D-glucose. In the zinc saccharate crystal, certain carboxylate and hydroxyl oxygens are coordi­nated to zinc atoms; the oth­ers project into the hydrophilic channels. The walls of the hy­drophobic channels, in con­trast, are surrounded by C-H bonds. The channels are iso­lated from each other: I2 vapor, for example, penetrates the hy­drophobic but not the hy­drophilic channels.

Nothing but Xe, Cp and H By dissociating acetylene molecules in a frozen xenon matrix using UV light or fast electrons, two research teams have independently found spectroscopic evidence for the formation of HXeCCH—for­

mally the insertion of xenon into a C - H bond. The work was reported by Leonid Khri-achtchev and coworkers at the University of Helsinki, Fin­land, and by Vladimir I. Feld-man's group at Karpov Insti­tute of Physical Chemistry and the Institute of Synthetic Polymeric Materials, both in Moscow I/. Am. Chem. Soc, 125,4696 and 4698 (2003)}. The Helsinki researchers, who relied on UV photolysis, also observed IR absorption bands they attributed to HXeCC and HXeCCXeH. The latter is the first neutral rare-gas hydride molecule containing two xe­non atoms. All three molecules were predicted to exist in a computational study coau-thored last year byjan Lundell, a member of the Helsinki team. The new molecules dif­fer from the vast majority of organoxenon compounds in that they do not contain fluo­rine. The two teams suggest that their work may open a new direction in synthetic organoxenon chemistry. But synthetic chemist Gary J. Schrobilgen of McMaster Uni­versity in Hamilton, Ontario, points out to C&EN that such molecular sightings don't pro­vide much insight into how to do this chemistry on a prepar­ative scale.

New Β vitamin identified Japanese scientists have added a new member to the family of Β vitamins that in-

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eludes niacin (vitamin B-3) and riboflavin (vitamin B-2) [Na­ture, 422, 832 (2003)1. Many enzymes rely on small organic molecules called cofactors to assist in redox catalysis. Hu­mans make some of these co-factors from scratch, but oth­ers —called vitamins—must be obtained through the diet. Tadafumi Kato, head of RIKEN's Laboratory for Mol­ecular Dynamics of Mental

Disorders, in Saitama, Japan, and postdoc Takaoki Kasahara demonstrate that pyrrolo-quinoline quinone (PQQ, shown) is required for the prop­er functioning of an enzyme that mice rely on to break down the amino acid lysine. PQQ's critical biochemical role, coupled with mammals' inability to synthesize it, qual­ifies PQQ as a vitamin, the au­thors suggest.

Crystal reveals dual personality X-ray diffraction studies of crystals of zinc saccharate show that its structure consists of a 3-D network with two distinct kinds of parallel channels. One type is hydrophilic and the oth­er hydrophobic, according to Richard Robson, chemistry professor at the University of Melbourne, Australia, and coworkers [Angew. Chem. Int.

SCIENCE & TECHNOLOGY ROUNDUP

• Naturally occurring 209Bi, • The Global Alliance for TE once considered the heaviest Drug Development will func stable isotope, has been caught a project at the Korean Re-radioactively decaying away— search Institute of Chemica albeit very slowly—by a team of Technology to synthesize anc French researchers [Nature, optimize novel quinolones foi 422, 876 (2003)]· The isotope first-line treatment of tuber-was suspected of being ra- culosis. Quinolones such ai dioactive, but until now a suffi- ofloxacin, levofloxacin, anc ciently sensitive detector had ciprofloxacin are currentl) not been made. The isotope de- used as second-line drugs tc cays by α emission to 205T1 and treat drug-resistant strains has ahalf-life of 1.9 Χ 1019years. This project is the first to de-That leaves 208Pb as the heavi- velop new quinolones specifi-est known stable isotope. cally for tuberculosis.

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