Protecting group found for hydroxyls, aminos
CHICAGO Scientists at the University of Kansas, Lawrence, have devised a reagent to protect hydroxyl and amino groups dur ing multistep syntheses. Postdoctoral fel low student Binghe Wang of the Univer sity of Kansas School of Pharmacy told the Division of Organic Chemistry that the protecting group thus attached is re movable by mild reducing agents when no longer wanted. Such a reagent is useful because chemists want to selectively protect groups that are removable by many dif-
ferent mechanisms. Such a choice en ables them to apply and remove each group by design, while sparing protect ing groups that are still needed. The new reagent is a quinonebutanoic acid, 3-methyl-3-(3,5-dimethyl-2-benzoquinone)butanoic acid. In use, research ers would form amides or esters of the carboxyl group. To remove the group, the derivative would be shaken for a few minutes with dilute aqueous sodium dithionite. This procedure reduces the qui none to a hydroquinone. A hydroquinone hydroxyl group maneuvers around to displace the amine or alcohol from the carboxyl group to form a coumarin, spe cifically 3,4-dihydro-6-hydroxy-4,4^,7-tetramethylcoumarin. The coumarin can be recovered and reoxidized to the quinone reagent. Working with medicinal chemistry professor Ronald T. Borchardt and post doctoral fellow Siming Liu, Wang makes the reagent in three steps and in 70% overall yield from commercially avail able 2,6-dimethylbenzoquinone.
Protecting group removable by reducing agents
Stephen Stinson
Progress made in design of zeolite synthesis
UÏM.M.NI Researchers haven't yet achieved the ability to design a synthetic route that would make a specific zeolite. But Mark E. Davis, professor of chemical engineering at the California Institute of Technology, Pasadena, believes it won't be long. Davis explored the outlook for zeo lite synthesis for the Division of Colloid & Surface Chemistry. Organic struc ture-directing agents can be designed, he says, and the required molecular building blocks are available. What re mains is to combine these elements with the chemical compatibilities that lead to self-assembly.
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ΤΎ Polyester
CH3
Quinone derivative
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rizzazz.
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DuPont DBE Intermediates
OH Coumarin derivative X = — O—} - N R R = group being protected, possibly a sugar or amino acid or a natural product
© 1993 DuPont Company
CIRCLE 2 7 ON READER SERVICE CARD SEPTEMBER 13,1993 C&EN
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