An Annulation Approach to the Synthesis of Pseudoguaianolide Sequiterpene Lactones. Total Syntheses of dl-Confertin and dl-Aromatin

Article abstract of DOI:10.1021/ja00265a035

Annulation of 2-methyl-1,3-cyclopentanedione with 4-(halomethyl)-5-(1-oxopropyl)-3-furancarboxylic esters 6a or 6b provides the fully assembled tricyclic framework, 1, of the cytotoxic pseudoguaianolide sequiterpene lactones.Dienedione 1 has been used to construct (+/-)-confertin (2) and (+/-)-aromatin (3).Experiments relevant to a total synthesis of the more complex helenanolides (e.g., the fastigilins, 4) also are discussed.