Semi-synthetic quassinoid

Polonsky et al [112] reported the effect of forty-six natural and semi-synthetic quassinoids, on feeding of tobacco budworm (HeliotMs virescens). Their activity is compared to that of the well-known antifeedant azadirachtin from Azadirachta indica Juss. 

The same assay was carried out for five semi-synthetic quassinoids, which were obtained by esterification of the C-15 OH group of desacetyl-isobrucein-B (124) as shown in Table 13. All ester derivatives showed higher antitumor promoting activity than that of the starting quassinoid, desacetyl-isobrucein-B (124). A compound containing a fluorinated aliphatic ester showed the highest potency [36]. 

Four semi-synthetic and fourteen quassinoids were tested for their antifeedant and insecticidal activity against 3rd instar larvae of the diamondback moth(Plutellaxylostella) [111]. 

---