Two Novel Alkaloids from the American Ladybug Hippodamia Convergens (Coleoptera, Coccinellidae)

Abstract

During our continuing investigation of Coccinellidae alkaloids [l, 2,3] about 20,000 specimens of Hippodamia convergens were collected in Central California in September 1971. Fractionation of the methanolic extract by solvent partitions and repeated column chromatography afforded two novel alkaloids, hippodamin (I) and convergin (11) in a ratio of about 1 : 2. 'The mass spectrum of hippodamin (I) indicates an empirical formula Cl3HZ3N and shows a fragmentation pattern nearly identical to that of the known alkaloid precoccinellin (111) [l] (that has been shown [2] to be 2-methyl-cis,trans,cis-perhydro9b-azaphenalene with the methyl group equatorial [4]) from which it is readily differentiated by TLC and minor features of the IR spectrum. The pmr spectra of 1 and I11 are likewise very similar, strongly suggesting that 1 is a stereoisomer of 111. The observation that hippodamin N-oxide and hippodamin hydrochloride are devoid of optical activity even at 300 nm establishes that I is either a symmetrical entity like 111 or a racemic mixture. The first hypothesis is excluded by the I3C NMR spectrum of hippodamin N-oxide, displaying chemical shifts very close to those observed for coccinellin (precoccinellin N-oxide) [2] but where the number of signals clearly establishes the lack of symmetry. We therefore propose that hippodamin is a 2-methyltrans, cis, cis-perhydro-9b-azaphenalene, found as a racemic mixture.The molecular weight of convergin (11) (M' = 209 by M.S.) is consistent with the formula C, ,Hz3N0. Its IR spectrum (5 % in chloroform) shows a prominent carbonyl band at 1680cm-' as well as a broad absorption at about 3200cm-I attributed to N-H stretching, as confirmed by acetylation of I1 to an N-acetyl derivative (~,=~1700, 1650 cm-I). The shift of the ketone carbonyl frequency implies the existence of a strong transannular interaction in 11. Convergin hydrochloride is devoid of carbonyl (by IR) and exists thus as the carbinolamine salt, a type of behaviour well documented by Leonard[5]. Treatment of convergin with LAH in refluxing THF affords in nearly quantitative yield an optically inactive derivative identical in all respects with natural hippodamin. The carbinolamine form of convergin is thus an hydroxyhippodamin with the OH function at a ring junction.

Transcriptome analysis reveals candidate genes involved in luciferin metabolism inLuciola aquatilis(Coleoptera: Lampyridae)

“…Different groups of beetles have been reported to produce different defensive compounds. In the family Coccinellidae (ladybugs), many compounds, e.g., coccinelline from Coccinella septempunctata ( Tursch et al, 1971 ), hippodamine from Hippodamia convergens ( Tursch et al, 1972 ), and propyleine from Propylaea quatuordecimpunctata ( Tursch, Daloze & Hootele, 1972 ) were identified. Both larva and adult leaf beetles (family Chrysomelidae) are also known to produce defensive compounds such as isoaxazolinone glucoside 5 and its 3-nitropropionate esters 6 to prevent them from natural enemies ( Pauls et al, 2016 ).…”

Combining two-directional synthesis and tandem reactions, part 11: second generation syntheses of (±)-hippodamine and (±)-epi-hippodamine

“…Hippodamine ( 1 ) is a naturally occurring alkaloid isolated from a ladybird beetle Hippodamia convergens by Tursch and co-workers in 1972. [ 3 ] The structure of hippodamine ( 1 ) was established two years later by the same group[ 4 ] on the basis of a single-crystal X-ray diffraction experiment (Figure 1 ). Epi-hippodamine ( 2 ) is its unnatural isomer with an axial C-5 methyl group.…”