A Unique Toxic Peptide from the Larvae of the South American Sawfly, Perreyia flavipes

A major toxic component of the South American sawfly larvae, Perreyia flavipes (Pergidae), has been shown to be a heptapeptide with the structure (1). The unique features of this peptide, which has been named pergidin, are the presence of five unnatural D amino acids and a phosphoseryl residue

Bioactivity and chemistry of the genus Hortonia

The dichloromethane extracts of the leaves, stem bark, bark and the roots of the three species of the primitive endemic genus Hortonia, H. angustifolia, H. floribunda and H. ovalifolia, collected from nine geographical locations ranging from lower elevations (84-420 m) to higher (2000 m) showed comparable HPLC profiles and mosquito larvicidal and antifungal activities; protein analysis of the leaves of the three species of Hortonia showed identical peaks and bands. The two major metabolites (4S)-4-methyl-2-(11-dodecynyl)-2-butenolide (2) and (4S)-4-methyl-2-(11-dodecenyl)-2-butenolide (3), which were previously reported from all three plants, showed potent larvicidal activities. Compound 2 was excessively high in the extracts of the stem bark and the roots of all three species amounting to approximately 38 and 60%, respectively. A minor new butenolide (4), (4S)-4-methyl-2-((2R)-hydroxy-11-dodecenyl)-2-butenolide, with much reduced larvicidal activity and ishwarane (1), which showed antifungal activity, were also isolated from all three plants. Treatment of compound 2 with H2/Pd-C afforded the completely reduced compound 5, which showed no larvicidal activity, indicating that unsaturation in both 2 and 3 is necessary for their bioactivity. The foregoing evidence showed that there are major similarities between the three species of Hortonia

A Triad of Bis(orthometalated) d⁸-Complexes Containing Four-Membered Rings

Reaction of 2-LiC6F4PPh2 with [MCl2(SEt2)2] in diethyl ether gives the monomeric bis(chelate) complexes trans-[M(κ2-2-C6F4PPh2)2] [M = Pt (1), Pd (2)] or, in the case of platinum, a mixture of cis- and trans-isomers. Treatment of a mixture of NiCl2 and 2-BrC6F4PPh2 in THF with zinc dust gives trans-[Ni(κ2-2-C6F4PPh2)2] (3). The four-membered chelate rings in 1−3 are opened on addition of the bidentate ligand 1,2-bis(diphenylphosphino)ethane (dppe), and, in the case of 3, 2,2′-bipyridine (bipy) and 1,10-phenanthroline (phen), to give complexes of the type cis-[M(κC-C6F4-2-PPh2)2(L-L)] [L-L = dppe, M = Ni (6), Pd (7), Pt (8); M = Ni, L-L = bipy (9), phen (10)], in which the PPh2 groups are uncoordinated. Complexes 6−8 show unexpectedly large four-bond coupling constants (4JPF), in the range 75−95 Hz, between the fluorine atoms (F6) ortho to the metal−carbon σ-bond and the phosphorus atoms of the PPh2 groups, possibly because F6 and the lone pairs on phosphorus adopt a close to synperiplanar conformation. Treatment of 2 with [PdCl2(NCMe)2] gives the dinuclear complex [Pd2(μ-Cl)2(κ2-2-C6F4PPh2)2] (11), which dimerizes in solution to the tetranuclear complex [Pd4(μ-Cl)4(μ-2-C6F4PPh2)4] (12) as a result of opening of the chelate 2-C6F4PPh2 rings. Carbon monoxide inserts into a nickel−carbon σ-bond of 3 to give, after oxidation, bis-2,2′-(diphenylphosphinoyl)octafluorobenzophenone, {2,2′-C6F4P(O)Ph2}2CO (14). The molecular structures of complexes 1−3, 6, 8, 9, and 14 have been determined by single-crystal X-ray methods