Pii: S0968-0896(98)00129-1

ÐAllatostatins are 6±18 amino acid peptides synthezed by insects to control production of juvenile hormones, which in turn regulate functions including metamorphosis and egg production. Four insect allatostatin neuropeptide analogues incorporating turn-promoting pseudopeptide moieties in the region responsible for biological activity were prepared by solid phase peptide synthetic methods. Bioassay indicated that activities approached those of the natural neuropeptides, and molecular models based on NMR data showed similar conformations and the presence of a b-turn in the active core region for the four analogues. Di€erences in activity are believed to be due to di€erences in bulk and relative position of atoms in the unnatural portion of the analogues, and their di€ering degrees of conformational freedom. The studies support the feasibility of development of neuropeptide-based insect control agents resistant to peptidase deactivation. # 1998 Published by Elsevier Science Ltd. All rights reserved.