Rosalind Y. Wong

Toxaphene Insecticide: A Complex Biodegradable Mixture

Adsorption and gas-liquid chromatography separate toxaphene into at least 175 polychlorinated 10-carbon compounds including Cl6, Cl7, Cl8, Cl9, and Cl10 derivatives. One toxic component is 2,2,5-endo,6-exo,8,9,10-heptachlorobornane. Rats metabolically dechlorinate toxaphene, removing about half of the chlorine from the technical insecticide and from each of seven subfractions of varying composition and toxicity.

Isolation and identification of the first C-17 limonin epimer, epilimonin.

Limonoids are a family of highly oxygenated triterpenoid secondary metabolites found in significant quantities in Citrus and reported to possess multiple health promoting properties. This is the first known report of the isolation and characterization of an epimer of limonin. The epimer, named epilimonin, was isolated by fractional crystallization from a mixture consisting mainly of limonin and epilimonin obtained as byproduct from our efforts to isolate limonin glucoside. Side-by-side comparison of the MS, IR, and (1)H and (13)C NMR data of epilimonin and limonin lead to the assignment of C-17 as the site of epimerization. An earlier study on the bioavailability of limonin glucoside in humans had indicated that limonin glucoside was metabolized to give limonin and a second limonin metabolite. Results from analyzing epilimonin by the same chromatographic conditions used for the bioavailability study suggest that the second limonin metabolite was epilimonin.

Methylene bisflavonoids from frond exudate of Pentagramma triangularis ssp triangularis

Abstract Fronds of a distinct chemotype of Pentagramma triangularis ssp. triangularis produce an exudate from which two novel flavonoids have been isolated. Common to both substances is a kaempferol-4′-methyl ether moiety bearing a C-8 methylene to which is attached in one instance a second kaempferol-4′-methyl ether moiety through the 8 position and in the other instance a dihydrochalcone moiety through the 3′ position. The structural assignments were made by means of spectral data and X-ray crystallographic analysis.

Lipase-catalyzed methanolysis of triricinolein in organic solvent to produce 1,2(2,3)-diricinolein.

The objective of this study was to find the optimal parameters for lipase-catalyzed methanolysis of triricinolein to produce 1,2(2,3)-diricinolein. Four different immobilized lipases were tested, Candida antarctica type B (CALB), Rhizomucor miehei (RML), Pseudomonas cepacia (PCL), and Penicillium roquefortii (PRL). n-Hexane and diisopropyl ether (DIPE) were examined as reaction media at three different water activities (aw), 0.11, 0.53, and 0.97. The consumption of triricinolein and the formation of 1,2(2,3)-diricinolein, methyl ricinoleate, and ricinoleic acid were followed for up to 48 h. PRL gave the highest yield of 1,2(2,3)-diricinolein. Moreover, this lipase showed the highest specificity for the studied reaction, i.e., high selectivity for the reaction with triricinolein but low for 1,2(2,3)-diricinolein. Recoveries of 93 and 88% DAG were obtained using PRL in DIPE at aw of 0.11 and 0.53, respectively. Further, NMR studies showed that a higher purity of the 1,2(2,3)-isomer vs. the 1,3-isomer was achieved at higher aw (88% at aw=0.53), compared to lower aw (71% at aw=0.11). The DAG obtained was acylated by the DAG acyltransferase from Arabidopsis thaliana. Therefore, this enzymatic product is a useful enzyme substrate for lipid biosynthesis. Accordingly, the use of PRL in DIPE at aw 0.53 is considered optimal for the synthesis of 1,2(2,3)-diricinolein from triricinolein.

The characterization and absolute stereochemistry of barbaline, a diterpenoid alkaloid from Delphinium barbeyi

The structure and absolute stereochemistry of a new diterpenoid alkaloid, barbaline, was determined by NMR spectroscopy techniques and single-crystal X-ray diffraction analysis.

Constituents of Tabebuia guayacan: The structure of guayacanin

Abstract The heartwood of T. guayacan has yielded tectol and a new, novel dibenz-xanthene derivative (guayacanin). The structure of guayacanin suggests its biogenetic derivation through the condensation of prenylnaphthalene quinols. The tetrahydro derivative of the xanthene was synthesized by an analogous acid catalyzed reaction of prenylnaphthalene quinol derivatives of lapachol and 1,4 naphthalene diol.

Irregular sesquiterpenoids from Ligusticum grayi roots

Root oil of Ligusticum grayi (Apiaceae) contains numerous irregular sesquiterpenoids. In addition to the known acyclic sesquilavandulol and a sesquilavandulyl aldehyde, two thapsanes, one epithapsane, and 14 sesquiterpenoids representing eight hitherto unknown carbon skeletons were found. These skeletons are: prethapsane, i.e. 1,1,2,3a,7,7-hexamethyloctahydro-1H-indene; isothapsane, i.e. 1,2,3a,6,7,7a-hexamethyloctahydro-1H-indene; ligustigrane, i.e. 1,1,2,7,7,7a-hexamethyloctahydro-1H-indene; isoligustigrane, i.e. 1,1,2,6,7,7a-hexamethyloctahydro-1H-indene; preisothapsane, i.e. 1,1,2,3a,6,7-hexamethyloctahydro-1H-indene; isoprethapsane, i.e. 1,1,2,4,7,7-hexamethyloctahydro-1H-indene; allothapsane, i.e. 1,1,2,3a,7,7a-hexamethyloctahydro-1H-indene; and oshalagrane, i.e. 1,1,2,4,6,6-hexamethylspiro[4.4]nonane. The bicyclic sesquiterpenoids are presumably biosynthesized by head-to-head coupling of geranyl diphosphate and dimethylallyl diphosphate, followed by a cyclization sequence leading to a hydroindane skeleton with six one-carbon substituents. Subsequent rearrangements--primarily methyl migrations--account for the remarkable variety of structures represented in L. grayi root oil.

Conformational analysis of 10α-cucurbitadienol

Evidence has been obtained on the solid state (determined by X-ray crystallography) and solution (determined by 1H and 13C NMR spectroscopy) properties of 10α-cucurbita-5,24-dien-3β-ol which indicate that the molecule orients into a bent rather than flat conformation, the 3β-OH group aligns into the unusual axial rather than the equatorial position, and the side chain orients into the right-handed conformation.

Quinones and quinone methides—IV: Dimerization reactions of 2-phenylmethyl-5-methoxy-1,4-benzoquinones

Abstract Base catalyzed dimerization of 2-(4-methoxyphenylmethyl)-5-methoxy-1,4-benzoquinone 6 yields as the chief product an unusual tetrahydroxanthen derivative 7a. The structure of 7a suggests that it is formed by combination of two molecules of the ortho-quinone methide tautomer of 6. Rearrangement of 7a yields the dihydro-oxepin derivative 15 and the indanspirocyclohexene derivatives 17 and 18a, all of which are formed as minor products in the dimerization of 6. In contrast to 6 related 2-(1-phenylethyl)-1,4-benzoquinones do not dimerize in basic media.

Ergostanoids from Petunia parodii

Abstract Leaves of Petunia parodii gave three new petuniolides, one of which has a 9,11-double bond. Of the other two, one has a 9β-OH with an 11,12-double bond and the second has a 9β, 19-cyclopropyl system as well as an 11β-OH and a 12-keto group. Also present are six new petuniasterones which arise from rearrangement of the D-ring epoxides, petuniasterones K and L. A 13,17- seco -petuniasterone was also present.