The synthesis of novel O-alkyl analogues of the energy-repartitioning [beta]-agonist clenbuterol and their physiological and immunological characterisations

Abstract

It was proposed that some O-alkyl analogues of the beta-adrenergic agonist clenbuterol would be effective structural and functional congeners of clenbuterol which may then be used for the production of clenbuterol-specific idiotypic antibodies. These antibodies could possibly then be used to generate anti-idiotypic antibodies that mimic the energy-repartitioning effects of clenbuterol. Therefore, the aim of this work was to synthesise and characterise these compounds, evaluate their physiological effects, characterise the specificity of antibodies produced in response to protein conjugates of two of the novel compounds, and then use this data to determine the utility of these compounds for the generation of anti-idiotype antibodies which mimic clenbuterol. The target compounds were synthesised in five steps from 3,5-dichloro-4-hydroxyacetophenone in overall yields of 5-28%. A synthetic scheme similar to that which has led to clenbuterol was used to form the phenylethanolamine backbone, with modifications to include the O-alkyl moiety via a modified Williamson ether synthesis, and elimination of a synthetic chlorination step. Overall, 15 new compounds were synthesised, which were characterised and their structure confirmed from proton and carbon-13 NMR, IR and mass spectral data. The two haptenic analogues were then conjugated to carrier proteins using carbodiimide-based chemistries. In conclusion, the results indicated that the O-alkyl analogues, although structurally similar, were ineffective functional mimics of clenbuterol. Therefore, the anti-clenbuterol antobodies produced from the novel O-alkyl analogues would appear to be unsuitable for production of anti-idiotypic antibodies that mimic the energy-repartitioning effects of clenbuterol since the antibodies were unable to distinguish between the compound which demonstrated energy-repartitioning effects (clenbuterol) and those that did not (O-alkyl clenbuterol analogues).