The synthesis and metathesis of a range of alkene containing, proline derived, substrates, in order to identify a substrate that could be used for the generation of a dynamic combinatorial library of peptidomimetic receptors, is described. The metathesis reactions of substrates containing an acryloyl group were found to be very slow, with little or no metathesis products being formed. Substrates containing an N-allylamide group were also found to be problematic during metathesis, with isomerisation / cleavage of this group occurring to fonn the corresponding enamides or amides. This isomerisation / cleavage reaction was found to be a fairly general process for a range of N-allylamides, however, under the conditions described, it only occurred to a small extent, thus it was not found to be a useful synthetic procedure. The metathesis of N-pent-4-enoylproline but-3-enylamide gave the most promising results, with LC-MS analysis indicating that complete consumption of the starting material had occurred to form both linear and cyclic oligomers, e.g. cyclic monomer, cyclic dimer(s), cyclic trimer(s) and linear dimer(s), with cyclic dimer(s) being the major product formed. Due to the polarity of these products and also the presence of ruthenium containing catalyst by-products, their purification / separation, by column chromatography and preparative HPLC, proved difficult. Investigations of the reversibility of the metathesis reaction were carried out using Npent-4-enoylproline but-3-enylamide, with LC-MS analysis being used to detect any changes that occurred in the product distribution. The reversible nature of the metathesis reaction was initially investigated under various reaction conditions, with the addition of ethene and a further portion of catalyst to the reaction mixture, after 48 hrs, resulting in the regeneration of some starting material, thus suggesting that the products formed during the metathesis of N-pent-4-enoylproline but-3-enylamide are recyclable. The synthesis of diastereomerically pure samples of the products formed from the metathesis of N-pent-4-enoylproline but-3-enylamide, via a non dynamic combinatorial route, was also attempted, in order to further investigate the reversible nature of the metathesis reaction. The trans isomers of two of the possible linear dimers were successfully prepared and were subjected to the standard metathesis reaction conditions. The metathesis of one of these linear dimers resulted in the formation of the expected cyclic dimer, while the other, in addition to the expected cyclic dimer, resulted in the formation of some reverse reaction products, i.e. cyclic monomer and N-pent-4enoylproline but-3-enylamide, thus further suggesting that the products fo1med during the metathesis of N-pent-4-enoylproline but-3-enylamide are recyclable.