Stereoselective synthesis and moulting activity of 2,3-diepi-20-hydroxyecdysone and 2,3-diepi-5α-20-hydroxyecdysone

The ecdysteroid analogues 2,3-diepi-20-hydroxyecdysone and 2,3-diepi-5α-20-hydroxyecdysone have been synthesized from the readily available ecdysteroid, 20-hydroxyecdysone, and moulting activity has been determined using the Musca bioassay. As expected, the 2,3-diepi-analogue was less active than the parent ecdysteroid, 20-hydroxyecdysone. However, the 2,3-diepi-5α-analogue, which was expected to be inactive in the assay, exhibited moulting activity though it was approximately 1.5-fold less active than its 5β-analogue. The activity of the 5α-analogue could possibly result from the ability of this compound to bind to the ecdysteroid receptor. Alternatively, a possible in vivo C-5 epimerization of the 2,3-diepi-5α-analogue to the corresponding 5β-analogue could account for its activity.