It is the (9β,10α) stereoisomer of ergosterol and was produced as a photochemical by-product in the preparation of vitamin D1, which was a mixture of vitamin D2 and lumisterol.
This compound is the (9β,10α) stereoisomer of ergosterol and was created as a secondary product resulting from the photoreaction used to produce vitamin D1, a mixture that also included vitamin D2 and lumisterol.