Chemical studies of rectal gland secretions of some species ofBactrocera dorsalis complex of fruit flies (diptera: Tephritidae)

Male-produced rectal gland secretions of a number of species now considered to be members of theBactrocera dorsalis complex of fruit flies have been examined by combined gas chromatography-mass spectrometry. The structures of a number of previously unreported compounds have been confirmed by synthesis and Chromatographic comparisons. Compounds identified in these secretions include fatty acids, esters, amides, keto alcohols, diols and spiroacetals. These chemical findings are in agreement with taxonomic revisions based on other criteria.

Synthesis and stereochemistry of some bicyclic gamma-lactones from parasitic wasps (Hymenoptera: Braconidae). Utility of hydrolytic kinetic resolution of epoxides and palladium(II)-catalyzed hydroxycyclization-carbonylation-lactonization of ene-diols

A palladium(II)-catalyzed hydroxycyclization-carbonylation-lactonization sequence with appropriate pent-4-ene-1,3-diols provides efficient access to the bicyclic gamma-lactones, 5-n-butyl- and 5-n-hexyltetrahydrofuro-[3,2-b]furan-2(3H)-ones (3) and (4), respectively, in both racemic and enantiomeric forms. Some of the substrate pent-4-ene-1,3-diols of high enantiomeric excess (ee) have been derived from racemic terminal epoxides by hydrolytic kinetic resolution (HKR) using cobalt (III)-salen complexes. (9Z,12R)-(+)-Ricinoleic acid also serves as a "chiral pool" source of other pent-4-ene-1,3-diols. These syntheses and enantioselective gas chromatography confirm the structures and absolute stereochemistry of the lactones in some species of parasitic wasps (Hymenoptera: Braconidae). The highly abundant 5-n-hexyltetrahydrofuro-[3,2-b]furan-2(3H)-one (4) in Diachasmimorpha kraussii and D. longicaudata is of high ee (>99%) with (3aR,5R,6aR) stereochemistry.

Synthetic studies of the HIV-1 protease inhibitive didemnaketals: stereocontrolled synthetic approach to the key mother spiroketals

The stereocontrolled synthesis of (2S,4R,6R,8S,10S,1'R,1' 'R)-2(acetylhydroxymethyl)-4,10-dimethyl-8(isopropenylhydroxymethyl)-1,7-dioxaspiro[5,5]undecane (4a) and its C1' '-epimer (4b), the key mother spiroketals of the HIV-1 protease inhibitive didemnaketals from the ascidian Didemnum sp., has been carried out through multisteps from the natural (R)-(+)-pulegone, which involved the diastereoselective construction of four chiral carbon centers(C-2, C-6, C-8, and C-1') by intramolecular chiral induce.

Carbon hydroxylation of alkyltetrahydropyranols: a paradigm for spiroacetal biosynthesis in Bactrocera sp

[figure: see text] In a number of Bactrocera species the penultimate step in the biosynthesis of spiroacetals is shown to be the hydroxylation of an alkyltetrahydropyranol followed by cyclization. The monooxygenases that catalyze this side chain hydroxylation show a strong preference for oxidation four carbons from the hemiketal center, to produce the spiroacetal. The hydroxy spiroacetals observed in Bactrocera appear to derive from direct oxidation of the parent spiroacetals and not from alternate precursors.

Chemistry of fruit flies: Glandular secretion ofBactrocera (Polistomimetes) visenda (Hardy)

The major component (>90% of volatiles) of the male rectal glandular extract of the nonpest speciesBactrocera visenda (Hardy) is 3-methyl2-butenyl acetate, with minor components being the isomeric 3-methyl-3-butenyl acetate, the homologous esters, 3-methyl-2-butenyl propanoate and 3-methyl-2-butenyl formate, along with 3-methyl-2-buten-1-ol, 3-methyl-2-butenal, and 3-methylbutyl acetate. None of these compounds has been identified previously from aBactrocera species, supporting the view thatBactrocera visenda is taxonomically distant from otherBactrocera species identified from the Australian mainland. This collection of compounds adds to the known types utilized by dipteran species and emphasizes their extensive biosynthetic capability.

Silylcuprate Routes to Cyclohex-2-enylsilanes

The efficacy of the dimethyl(phenyl)silylcuprate and (to a lesser extent) the methyl-diphenylsilylcuprate reagents in converting cyclohex-2-enyl chlorides into the corresponding allylsilanes has been investigated. The presence of copper(I) greatly suppresses formation of the coupled hydrocarbon, and promotes stereo- and regio-selective carbon-silicon bond formation, in a predominantly anti-SN2′ manner. Spectroscopic characterization of the diastereomeric silanes is presented. Grignard routes to some of these silanes are described.

Carvone- and Piperitone-Derived Allylic Stannanes and Aspects of Their Electrophilic Substitution

cis - and trans- Carvotanacetols and - piperitols have been converted into the corresponding allylic chlorides, which were made to react with both trimethyltinlithium and triphenyltinlithium . The resulting allylic stannanes were characterized by 1H, 13C and 119Sn n.m.r . spectroscopy, which permitted assignment of the relative configurations. Triphenyltinlithium appears to react in a (substantially) concerted fashion with the (optically active) chloride from the carvotanacetols yielding an optically active stannane . The corresponding trimethylstannane is optically inactive. Substitution reactions (SE′) with acid and sulfur dioxide (in chloroform) are preferentially γ-anti and specifically γ- syn respectively, in line with conclusions based on other cyclohex-2-enyl systems.

Stereochemical Aspects of Aldehyde Additions to Cyclohex-2-Enylstannanes

Cyclohex-2-enylation of aldehydes, mediated with boron trifluoride etherate, involves γ-equatorial approach of the presumed aldehyde-Lewis acid adduct (RCHO-BF3), irrespective of starting stannane stereochemistry. Marginal threo selectivity characterizes homoallyl alcohol formation from benzaldehyde, whereas alkanals react with high erythro selectivity, so that 1-(1′-hydroxyalkyl)cyclohex-2-enes in this diastereomeric form are available based on allyltin chemistry.

Synthesis and electrophilic substitution of some Hexa- and Penta-2,4-dienyl-silanes,-germanes and -stannanes

Penta-2,4-dienyl and hexa-2,4-dienyl derivatives of silicon, germanium and tin have been synthesized (normally as E/Z mixtures) by metalation of the corresponding pentadienyllithium reagents. The E/Z isomeric mixtures have been fully characterized by 1H and 13C nuclear magnetic resonance spectroscopy. Trifluoroacetolysis of these compounds (CF3COOD) has been studied by direct 2H n.m.r. spectroscopy, and ε-electrophilic attack is predominant. In contrast, sulfur dioxide insertion (with the stannanes) is γ-regiospecific, but these kinetic γ-sulfinates rearrange, by a presumed electrocyclic process, to the conjugated dienylmethylsulfinates.

Stannylation and germylation of some 4-, 5- and 6-Alkylcyclohex-2-enyl chlorides

The allylic alcohols, trans-5-t-butylcyclohex-2-enol, trans-4-t-butylcyclohex-2-enol and trans-4- methylcyclohex-2-enol, have been converted into cyclohex-2-enyl chlorides by reaction with thionyl chloride and N-chlorosuccinimide-dimethyl sulfide. The stereochemistry of the allylic chlorides has been determined by 1H and 13C nuclear magnetic resonance spectroscopy. Stannylation of these chlorides with trimethyltinlithium, and triphenyltinlithium, has been examined and the resulting stannanes fully characterized by 1H, 13C and 119Sn n.m.r, spectroscopy, and electrophilic cleavage (acidolysis with deuterated trifluoroacetic acid) to the corresponding deuterocyclohexenes. A less extensive study of germylation (trimethylgermyllithium in hexamethylphosphoramide) was conducted also, and the allylic germanes fully characterized. Triphenyltinlithium and trimethylgermyllithium exhibit higher levels of stereo- and regio-specificity in chloride displacement than trimethyltinlithium.

Carbon magnetic resonance studies of some phenyl, furyl and thienyl organometallics. Some comments on carbon-metal scalar coupling

13C chemical shift variations within a series of phenyl, furyl and thienyl Group IVB organometallics appear to be best understood in terms of the usual alkyl and aryl substituent effects on 13C chemical shifts and not variations in dπ ?pπ metal-aryl interactions. Large changes in 13C-metal scalar coupling constants have been observed suggesting that other factors besides the s-character of the carbon-metal bond is responsible in determining the coupling constant.

Substituent effects by carbon-13 nuclear magnetic resonance: Concerning the π-inductive effect

13C Substituent chemical shifts (scs) data for the C4 and C10 carbon atoms in 1-x-naphthalenes and 9-x-anthracenes respectively do not corroborate the proposal that the meso disposition in anthracene is a suitable model for the detection of the π-inductive or inductomesomeric effect.

Organotin complexes with ethyl and benzyl sulphoxides

A series of complexes of methyltin halides with dibenzyl, diethyl, and methyl benzyl sulphoxides has been prepared and characterized. Vibrational and proton magnetic resonance spectra have been employed to allow suggestions as to the structures of the complexes. The change from dimethyl sulphoxide to sulphoxides with larger steric requirements and presumably dissimilar basicities is sufficient to allow the isolation of complexes of different stoicheiometries and structures. The magnetic inequivalence of the methylene groups Banking sulphur is influenced seriously by oxygen coordination to tin.

The configurations and P.M.R. spectra of iodo lactones and oxymercurials derived from some 5-Norbornene-2-endo-carboxylic acids

Iodo lactones and chloromercuri lactones derived from a number of 2- and 3-methyl-5-norbornene-2-endo-carboxylic acids have been prepared and characterized. Analyses of 60-MHz and 100-MHz proton magnetic resonance spectra have estab- lished their configurations, which conform to a general pattern of trans-addition. Criteria for stereochemical assignments in this system can be based upon identifiable vicinal, geminal, and some long-range 1H-1H and 1H-199Hg coupling constants. These criteria are used to establish that 5-norbornene-2-endo,3-endo-dicarboxylic acid and its derivatives do not follow the cis-oxymercuration route previously suggested.

Complexes of methyl-tin and -lead halides with substituted pyridine N-oxides

Complexes of some methyl-tin and -lead halides with a range of 4-substituted pyridine N-oxides have been prepared and characterized. The fluctuations in v(N-O) and in J(CH3-M) have been examined as a function of substituent, and the resonance positions of ring protons in the proton spectra are discussed.

A re-evaluation of the proton magnetic resonance spectra of some olefinmercury(II) systems

The 60-MHz and 100-MHz proton spectra of some oxymercurials derived from ethylene and propylene have been examined. Such spectra, contrary to other reports, provide no evidence for the existence of the mercurinium ion in detectable amounts. A more plausible interpretation of the spectra is presented.

Nuclear magnetic resonance of some fluoro-substituted phenyl and benzyl mercurials

l9F and lH nuclear magnetic resonance data are reported for the para and meta fluoro-phenyl and -benzyl mercurials of types R2Hg and RHgX where X is a halide. The 19F data for the fluorophenyl mercurials provide no evidence for direct aryl-mercury conjugation, and mercuri substituents exert very feeble electronic effects. The shielding for the fluorobenzyl mercurials suggests a quite pronounced o-p electron donating effect for the metallomethyl group (NCH2-). Some 199Hg-lH spin coupling constants are derived from the proton spectra of the benzyl mercurials.

Kinetics and mechanisms of mercuration of aliphatic carboxylic acids

The kinetics of the mercuration of acetic acid by mercuric acetate under anhydrous and aqueous conditions have been studied. The reaction is first order in mercuric acetate and possibly first order in acetic acid. Radicals are not involved. The reaction is insensitive to added salts and is not catalysed by acetate. Enol or carbanion intermediates are excluded by the absence of H-D exchange. A four-centre (SF2) mechanism is suggested. The reaction is accelerated by perchloric acid and this is attributed to mercuration by acetoxymercuric perchlorate probably in the form of an ion pair. Mercuric perchlorate and mercuric nitrate are more effective mercurating agents than mercuric acetate. Although the perchloric acid catalysed reaction may follow the SE2 mechanism an SF2 pathway is preferred. Propionic acid is mercurated exclusively at the α-carbon atom and trimethylacetic acid is unreactive. Acetic acid is 2.7 times as reactive as propionic acid. Optically active methylethylacetic acid appears to be mercurated stereospecifically.

199Hg-1H Spin-spin coupling in vinyl and ethynyl mercurials

The proton magnetic spectra of cis and trans-2-chlorovinylmercuric chloride, bis(trans-2-chlorovinyl)mercury, and methylethynylmercury have been determined. Large variations in the 199Hg-1H spin-spin coupling constants are observed for different hybridization states and different geometries.

Kinetics of the Decomposition of Sulphur Dicyanide in Aqueous Solution

The kinetics and stoicheiometry of the decomposition of aqueous solutions of sulphur dicyanide have been studied at temperatures between 0-70 �C and in media ranging from dilute perchloric acid to pH 7. The predominant reaction is nucleophilic substitution at carbon, but in perchloric acid solutions an alternative reaction path has been revealed.