Insect moulting hormones. LIV. The synthesis and biological acitvity of some alkylated ecdysone analogues

Abstract

A number of ecdysone analogues were prepared, with alkyl substituent groups projecting above and below the plane of the A-ring of the analogue (37), to gain an insight into the steric requirements for the binding of ecdysteroids to the hormone receptor. Moulting hormone activities of these analogues, determined with the Calliphora bioassay, revealed that the β-face is more sensitive to projecting alkyl groups than the α-face. It is concluded that binding of the hormone to the receptor probably takes place on both sides of the A-ring but that a close fit is more important on the β-face than the α-face.