Asymmetric Total Syntheses of (+)-Mycoepoxydiene and Related Natural Product (−)-1893A:  Application of One-Pot Ring-Opening/Cross/Ring-Closing Metathesis to Construct Their 9-Oxabicyclo[4.2.1]nona-2,4-diene Skeleton

The total syntheses of (+)-mycoepoxydiene and (−)-1893A have been completed. The present synthetic strategy features the use of one-pot ring-opening/cross metathesis (ROM/CM) followed by a ring-closing metathesis (RCM) reaction, allowing for the concise construction of the 9-oxabicyclo[4.2.1]nona-2,4-diene framework from a 7-oxabicyclo[2.2.1]hept-2-ene derivative and 1,3-butadiene. The sequential metathesis product was converted into (+)-mycoepoxydiene through the oxidative rearrangement of a furfuryl alcohol to a pyranone, thereby establishing its absolute stereochemistry. From the common intermediate, a structurally related natural product (−)-1893A was also synthesized via the vinylogous aldol reaction.