De novo designed contrasteric Diels–Alder reactions of 5-(2-oxazolynyl)-1,2,3,4,5-pentamethylcyclopentadiene

5-(2-Oxazolynyl)cyclopentadiene was designed on the basis of the orbital mixing rule to react with dienophiles with highly contrasteric manner in Diels–Alder reactions. The design was validated by the synthesis and reactions of the corresponding pentamethyl derivative, 5-(2-oxazolynyl)-1,2,3,4,5-pentamethylcyclopentadiene, to afford the products with the ratios of syn/anti=89–93/11–7.