The Diels–Alder adduct between ergosterol and 4-phenyl-1, 2, 4-triazolin-3, 5-dione is reconverted into ergosterol in high yield by reduction with lithium aluminium hydride. The adduct has been used in a synthesis of ergosta-5, 7, 22, 24 (28)-tetraen-3β-ol. An analogous synthesis of ergosta-5, 7, 22, 24 (28)-tetraen-3β-ol using radioactive intermediates enabled the intermediacy of this compound in ergosterol biosynthesis in yeast to be demonstrated.
