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The method, which has earned the “hot paper” status by the editorial
board of the prestigious scientific journal Angewandte Chemie
International Edition where the research will be published, consists
in constructing a template on which the molecule with the desired
structure is assembled. Specifically the objective was to form a
macrocycle, that is, a ring-shaped molecule. The annular structure is
fundamental when it comes to achieving certain properties. In fact
numerous drugs, such as anti-carcinogenics or antibiotics, have a
cyclic structure.
Now the question is, how can a ring on a molecular scale be
constructed? To date, there have been mainly two approaches. One of
them relies on chance: group the molecules that are to integrate the
final compound together and wait for them to assembly and form an
annular structure. “That’s almost like dropping a thread and hoping it
will form a circle when it lands. Some statistical laws intervene here,
but they do not guarantee more than 10% effectiveness for that to
happen”, indicates Santiago Luis, professor of the Department of
Inorganic and Organic Chemistry at UJI and the researcher responsible
for the study. In short, only 10 out of 100 molecules end up forming a
ring shape.
The second approach involves the use of templates around which the
molecular ring is assembled. Those most widely used to date have been
the positively or negatively charged atoms. The problem is that these
spherical templates offered by nature have fixed diameters and this
results in a limited set of templates which leaves little room for
refinements. “These spherical systems oblige us to make completely
symmetric molecules, and what we’re really interested in is in playing
with form”, adds Santiago Luis.
The novelty of this technique presented by the UJI researchers lies in
the fact that it is the first time that an anionic organic template (negatively
charged) is used to prepare ring-structured pseudoprotein compounds.
The idea is to construct a molecule which acts as a chemical negative
for the molecule that we wish to obtain, thus serving as a structure
around which the latter can be constructed. This works in a similar
fashion to the way jewellers create a circular mould around which
molten gold takes the ring shape intended.
“The election of an appropriate molecular template allows us to obtain
these structures with high selectivity and effectiveness. We are
talking about effectiveness between 80% and 100%”, Santiago Luis
affirms. The main contribution of the UJI group work is, precisely, to
leave behind the work with set molecular templates and open the way to
directed template modification. This is why the editors of Angewandte
Chemie International Edition are interested in highlighting this
finding.
“What we’ve done is to conceptually prove that we can design and
construct anionic organic templates that we can use perfectly well to
favour a given chemical reaction”, Santiago Luis concludes.
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