No abstract

No abstract

The secretion of the defensive glands of adults of the chrysomelid beetle Platyphora ligata from Panama has been shown to contain, besides chlorogenic acid (1) and a mixture of phosphatidylcholines, two new oleanane triterpene saponins, named ligatosides A and B. Their structures were established as 3-O-beta-D-glucuronopyranosyl-16alpha,23-dihydroxyoleanol ic acid-28-O-2-(3,4-dimethoxybenzoyl)-beta-D-glucopyranoside (2) and 3-O-beta-D-glucopyranosyl-(1-->2)-beta-D-glucuronopyranosyl-16a lpha, 23-dihydroxyoleanolic acid-28-O-2-(3, 4-dimethoxybenzoyl)-beta-D-glucopyranoside (3), respectively, by a combination of extensive 1D and 2D NMR methods (COSY, HMQC, HMBC, and TOCSY) and FABMS. This is the first report of triterpene saponins in the defensive secretion of an insect.

The alkaloids of two coccinellid beetles, Calvia14‐guttata and C.10‐guttata have been studied. The major alkaloid of these two species is the new piperidinic cis‐lactone 1a, for which the name calvine has been coined. The corresponding trans‐lactone 1b (2‐epicalvine) is also present as a minor constituent (±10%) in both species. We report here the structure determination and the total synthesis of these compounds. Kept in methanolic solution, these lactones undergo epimerisation as well as opening of the lactone ring leading to a complex mixture of nine main components.