MOLECULAR RECOGNITION: SYNTHETIC RECEPTORS BY RATIONAL DESIGN AND TARGETED SYNTHESIS

摘要

The preceding sections have given several examples of receptors which were rationally conceived and which behaved largely as expected. However, it is important not to generate a false impression - disappointments are common and many problems remain. They are especially acute when we target complex substrates such as carbohydrates. The selectivity of 24 for cellobioside is pleasing, but it is also quite exceptional. Moreover, we have no comparable designs for lactoside, maltoside or the many other disaccharide units. Molecular modelling may eventually remove some of the uncertainties, but further developments are needed. Current methodology can predict a single structure with good accuracy, but complexes cannot be understood without surveying all possible arrangements of all possible conformations of substrate and receptor, taking account of solvation, and considering entropy as well as enthalpy. This may be possible at some stage, in which case rational design will have come of age. However, in the medium term it seems an alternative approach may be needed. The methods of combinatorial chemistry have recently been applied to the problem and may present the best chance of a good, general solution. In any case, the study of molecular recognition through synthetic receptors will continue to attract interest, and will certainly stimulate further discoveries of relevance to molecular electronics.