University of Warwick Chemist Dr Andrew Clark has devised a method of creating medically useful linked rings of atoms that do not rely on the toxic, expensive, environmentally unfriendly methods used until now.

A large number of biologically and or medicinally active chemicals (e.g drugs and naturally occurring biological molecules) contain rings of atoms linked together. If we wish to treat diseases by the discovery of new drugs or design new "smart" materials it is of vital importance that chemists can construct these rings of atoms efficiently. One approach to making rings is that of stitching two ends of a chain of atoms together via a reactive molecule called a "free radical". Virtually all free radical reactions use other chemicals to "initiate" the construction process. Most procedures use one initiator in particular, called "tributyl tin hydride", however it has the following disadvantages:

• It is highly toxic.
• It is quite expensive.
• A large quantity of the chemical is normally required.
• It is destroyed in the stitching process and its remaining toxic residues are often difficult to separate (i.e. uneconomic) from the final desired ring product.
• Once finally separated from the desired ring product it is necessary to dispose of large amounts of the toxic chemical residues (i.e. it is environmentally unacceptable).

Andrew Clark and his fellow researchers have developed an alternative chemical based upon copper to control and initiate the stitching process. The new mediator is very cheap (900 times less expensive). It is just as efficient as the old initiator, even when the team use ten times less. The new chemical is also a catalyst which means that it is not destroyed in the stitching process. The catalyst can be easily recovered from the reaction and it can be re-used again in other reactions. Consequently, as a bonus there are no toxic residues to dispose of. The team will
'"/>

Contact: Dr Andrew Clark
A.J.Clark@warwick.ac.uk
+44 1203 523242
University of Warwick
5-Dec-1997