3,beta-Hydroxy-5agr-cholestan-6-one: A Possible Precursor of agr-Ecdysone Biosynthesis.

The conversion of cholesterol into 3beta-hydroxy-5alpha-cholestan-6-one has been demonstrated to occur in prothoracic glands of last instar larvae of the silkworm, Bombyx mori. Incubation of glands containing radiolabeled 3beta-hydroxy-5alpha-cholestan-6-one results in the disappearance of this sterol from the glands and the concomitant appearance of radiolabeled alpha-ecdysone in the medium. The observations suggest that the sterol is an intermediate in the synthesis of alpha-ecdysone.