title: Synthesis and binding to tubulin of colchicine spin probes.
abstract: Spin probes of deacetylcholchicine (1), 4-(hydroxymethyl)colchicine (2), and colchifoline (3) have been synthesized to study the binding site for colchicine on tubulin. Acylation of 1-3 with (+/-)-2,2,5,5-tetramethyl-1-pyrrolidinyloxy-3-carboxylic acid (4) afforded diastereomeric mixtures of the esters 5-8 and the amides 9 and 10. Pure diastereomers of 3 were synthesized with 4a and 4b, which inhibited the binding of colchicine by 60%. In the presence of calf brain microtubular protein, the colchifoline spin labels underwent reduction of the nitroxide group, which precluded their use to study the topography of the colchicine binding site.
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000378:metabolism; D003078:Colchicine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D004578:Electron Spin Resonance Spectroscopy; D007202:Indicators and Reagents; D013058:Mass Spectrometry; D008870:Microtubules / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D013113:Spin Labels / Q000138:chemical synthesis*; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014404:Tubulin / Q000378:metabolism*
chemical_list: D007202:Indicators and Reagents; D013113:Spin Labels; D014404:Tubulin; C003707:trimethylcolchicinic acid methyl ether; C043919:4-(hydroxymethyl)colchicine; C043920:colchifoline; D003078:Colchicine