Asymmetric synthesis of naturally occurring (−)-seimatopolides A and B

Asymmetric total synthesis of polyhydroxylated naturally occurring nonenolide seimatopolide A (3S,6S,7S,9R) and seimatopolide B (3S,6R,9R) is described in this article. An E-selective cross metathesis (CM) reaction between two suitable fragments followed by macrolactonization reaction is the main highlight of our synthesis for the two natural products. The fragment containing 6S,7S,9R stereocenters for seimatopolide A has been synthesized from l-tartaric acid as a chiral pool starting material, by employing (R)-CBS-mediated stereoselective keto reduction reaction. Another fragment, which is common for both the molecules, containing the 3S stereocenter was prepared by ME-DKR (metal enzyme combined dynamic kinetic resolution) method. The fragment having 6R,9R stereocenters for seimatopolide B has been prepared from n-decanal by adopting (R)-CBS-mediated keto reduction and Brown asymmetric allylation reaction.