Confirmation of the Revised Structure of Samoquasine A and a Proposed Structural Revision of Cherimoline.

The identity of the natural product samoquasine A has remained obscure since its isolation from custard apple seeds in 2000. One of the proposed structures, benzo[ f]phthalazin-4(3 H)-one, was prepared in two steps by regioselective ortho-lithiation/formylation of N, N-diisopropyl-2-naphthylamide, followed by cyclization with hydrazine, but was shown to be different from the natural product. Perlolidine, another candidate structure, was synthesized by a novel route involving a ß-selective Heck reaction of butyl vinyl ether. Both perlolidine and samoquasine A are converted by trimethylsilyldiazomethane into the same N-methyl derivative. In addition, the 13C NMR spectra of perlolidine and another structurally mis-assigned natural product, cherimoline, are almost identical. Thus, both samoquasine A and cherimoline are actually perlolidine.

Solar irradiation of the seed germination stimulant karrikinolide produces two novel head-to-head cage dimers.

Karrikinolide is a naturally derived potent seed germination stimulant that is responsible for triggering the germination of numerous plant species from various habitats around the world. We now report that solar irradiation of karrikinolide yields two novel head-to-head cage photodimers with the formation, stability and bioactivity of both presented herein.

Antiplasmodial activity of atisinium chloride from the Bhutanese medicinal plant, Aconitum orochryseum.

ETHNOPHARMACOLOGICAL RELEVANCE: The plant Aconitum orochryseum Stapf. (Ranunculaceae) is employed together with other plants in Bhutanese traditional medicine and is indicated for malaria-associated fever. AIM OF THE STUDY: To study the in vitro antiplasmodial activity of atisinium chloride, the major alkaloid from Aconitum orochryseum. MATERIALS AND METHODS: Atisinium chloride was extracted and purified from aerial parts of Aconitum orochryseum and its structure and absolute configuration confirmed by single crystal X-ray crystallography. The crude methanol extract, crude alkaloid fraction, and atisinium chloride were tested for in vitro antiplasmodial activity against the malarial Plasmodium falciparum strains TM4/8.2 (TM4; wild type) and K1CB1 (K1; chloroquine and antifolate resistant). RESULTS: The diterpenoid alkaloid atisinium chloride was shown to have moderate antiplasmodial activities with IC(50) values of 4 microM and 3.6 microM, respectively against the TM4 strain and the K1 strain of Plasmodium falciparum. CONCLUSIONS: Our studies provide the first evidence in support of one of the indicated treatments with Aconitum orochryseum in Bhutanese traditional medicine. This alkaloid also represents a potential new antimalarial structural lead.

A new dihydrodibenzodioxinone from Hypericum x 'Hidcote'.

One new compound, 4-hydroxy-4a,7-dimethoxy-4,4a-dihydrodibenzo-p-dioxin-2(3H)-one (1), was isolated from the aerial parts of the hybrid Hypericum x 'Hidcote', together with 8 known compounds: caryophyllene-4,5-epoxide, quercetin, quercitrin, quercetin-3-O-beta-D-galactopyranoside, epicatechin, betulinic acid methyl ester, beta-sitosterol and beta-sitosterol glucoside. The structure of the new compound, as well as its absolute configuration, was established by means of spectroscopic data analyses, including 2D NMR spectroscopy and X-ray structural analysis.

Assembling novel heterotrimetallic Cu/Co/Ni and Cu/Co/Cd cores supported by diethanolamine ligand in one-pot reactions of zerovalent copper with metal salts.

The three novel heterotrimetallic complexes [Ni(H2L)2][CoCu(L)2(H2L)(NCS)]2(NCS)2 (1), [Ni(H2L)2][CuCo(L)2(H2L)(NCS)]2Br2.2H2O (2), and [CuCoCd(H2L)2(L)2(NCS)Br2].CH3OH (3) have been prepared using zerovalent copper; cobalt thiocyanate; nickel thiocyanate (1), nickel bromide (2), or cadmium bromide (3); and methanol solutions of diethanolamine in air. The most prominent feature of the structures of 1 and 2 is the formation of the "pentanuclear"aggregate [[Ni(H2L)2][CoCu(L)2(H2L)(NCS)]2]2+ made up of two neutral [CoCu(L)2(H2L)(NCS)] units and the previously unknown cation [Ni(H2L)2]2+ "glued together" by strong complementary hydrogen bonds. With Cd2+ instead of Ni2+, a different structure is obtained: the [CoCu(L)2(H2L)(NCS)] unit is now linked to the Cd center through coordination of the oxygens of L groups on the Co atom to form the discrete heterotrimetallic molecular species 3. Cryomagnetic measurements of the compounds show that, in all cases, the magnetic behavior is paramagnetic; the polycrystalline EPR spectra contain signals due to monomeric copper species only. At the same time, the EPR spectra of frozen DMF and methanol solutions of 1-3 reveal the presence of triplet-state species that can be generated only by a coupling of the Cu2+ centers within a dimer. The species responsible for the appearance of transitions within the triplet state are thought to be Cu(II) dimeric centers formed by aggregation of two [CuCo(H2L)(L)2] fragments of 1-3 present in solution. The residual monomeric spectra in the g approximately 2 region are indicative of the existence of an equilibrium in solution between the dimeric and monomeric Cu(II) centers in aggregated and free [CuCo(H2L)(L)2] fragments, respectively, with varying degrees of stability. The fragmentation process of 1-3 in solution was screened by electrospray ionization mass spectrometry.

rac-Eudesm-7(11)-en-4-ol.

The isolation and structural determination of rac-eudesm-7(11)-en-4-ol, C15H26O, from the steam distillate of the flowers of Dipterocarpus cornutus Dyer (Dipterocarpaceae) is described. The structure was determined from spectroscopic data and a single-crystal X-ray study. Two similar independent molecules comprise the asymmetric unit of the structure.

Stemocurtisine, the first pyrido[1,2-a]azapine Stemona alkaloid.

A new pentacyclic stemona alkaloid, stemocurtisine (2), with a novel pyrido[1,2-a]azapine A,B-ring system, has been isolated from a root extract of Stemona curtisii. The structure and relative stereochemistry was determined by spectral data interpretation and X-ray crystallography.