Structure elucidation and chemical synthesis of stigmolone, a novel type of prokaryotic pheromone

Approximately 2 mu mol of a novel prokaryotic pheromone, involved in starvation-induced aggregation and formation of fruiting bodies by the myxobacterium Stigmatella aurantiaca, mere isolated by a large-scale elution procedure. The pheromone was purified by HPLC, and high-resolution MS, IR,H-1-NMR, and C-13-NMR mere used to identify the active substance as the hydroxy ketone 2,5,8-trimethyl-8-hydroxy -nonan-4-one, which has been named stigmolone, The analysis was complicated by a solvent-dependent equilibrium between stigmolone and the cyclic enol-ether 3,4-dihydro-2,2,5-trimethyl-6-(2-methylpropyl)-2H-pyran formed by intramolecular nucleophilic attack of the S-OH group at the ketone C4 followed by loss of H2O. Both compounds were synthesized chemically, and their structures mere confirmed by NMR analysis, Natural and synthetic stigmolone have the same biological activity at cn. 1 nM concentration.