Studies on the Syntheses of Sesquiterpene Lactones. 11. The Syntheses of 3-Epizaluzanin C, Zaluzanin C, Zaluzanin D, and Related Compounds 3&α-Hydroxyguaia-1(10),4(15),11(13)-trieno-12,6&α-lactone and 3&α-Hydroxyguaia-4(15),9,11(13)-trieno-12,6&α-lactone

Article abstract of DOI:10.1021/jo00269a039

3-Epizaluzanin C (10), 3α-hydroxyguaia-1(10),4(15),11(13)-trieno-12,6α-lactone (36), and 3α-hydroxyguaia-4(15),9,11(13)-trieno-12,6α-lactone (37) have been synthesized in 4.0percent, 3.0percent, and 1.7percent overall yields, respectively, from α-santonine (13) in 14 steps.Zaluzanin C (11) and zaluzanin D (12) have also been synthesized in 2.4percent and 2.5percent overall yields from α-santonin (13) in 16 steps and 15 steps, respectively.The key step involves the solvolytic rearrangement of (11S)-3α,4α-epoxy-1β-(mesyloxy)eudesmano-13,6α-lactone (27).The stereochemistry of3-epizaluzanin C (10), zaluzanin C (11), and zaluzanin D (12) have been established by these stereospecific syntheses.