Boat-chair conformational preference of exo, exo-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid

The ¹H and ¹³C nmr spectra of $\text{exo}$, $\text{exo}$-9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d₆ or alkaline D₂O, clearly show that it exists in a $\text{boat}$-$\text{chair}$-conformation with $\text{equatorial}$ carboxyl groups, thus being the first case of $\text{boat}$-$\text{chair}$ preference of a bicyclo[3.3.1] nonan-9-one due to the presence of $\text{exo}$,$\text{exo}$-2,4- substituents.     

[2+2] Cycloaddition of benzyne to cis,trans- and cis,cis-1,5-cyclooctadiene

The relative rates of formation of $\text{cis}$ and $\text{trans}$ [2+2]cycloadducts of benzyne to $\text{cis}$, $\text{trans}$- and $\text{cis}$, $\text{cis}$-1,5-cyclooctadiene, $\text{trans}$- and $\text{cis}$-cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described.     

Diastereoselective synthesis of N-acetyl-D,L-acosamine and N-benzoyl-D,L-ristosamine

N-Acyl derivatives of $\text{D}$,$\text{L}$-acosamine and $\text{D}$,$\text{L}$-ristosamine were synthesized with high stereo selectivity utilizing intramolecular Michael addition of γ- and δ-carbomoyloxy-α,β-unsaturated esters.     

Synthesis of the enantiomeric forms of cis and trans 1-benzyloxy-2,3-epoxy butane and of (3S,4S) 4-methyl-3-heptanol

The C₄erythro and threo diols (7) and (8) are converted either into the chiral epoxides (13) and (15) or into the enantiomers (14) and (16); the epoxide (13) is used as chiral synthon for the preparation of (3$\text{S}$,4$\text{S}$) 4-methyl-3-heptanol (21).     

Preparation of halo-F-methanes via potassium fluoride-halogen cleavage of halo-F-methylphosphonium salts

Treatment of halo-$\text{F}$-methylphosphonium salts with potassium fluoride and halogen (I₂, Br₂, ICl, IBr) gives modest yields of halo-$\text{F}$-methanes. This method of preparation augments the classical Hunsdiecker approach to these materials.     

New highly oxidized fusicoccane diterpenoids from the liverwort plagiochilaacanthophylla subsp. japonica

Four novel fusicoccane diterpenoids, fusicoplagins A, B, C, and D, have been isolated from the liverwort $\text{Plagiochila}$$\text{acanthophylla}$ subsp. $\text{japonica}$ and the structures determined by spectroscopic methods, chemical transformations, and X-ray crystallographic analysis.     

Autorecycling oxidation of alcohol catalyzed by 1,3,7,9,11,12,14-heptazapentacene-2,4,8,10 (14H,3H,9H,12H)-tetraones (mixed flavins)

1,3,7,9,11,12,14-Heptazapentacene-2,4,8,10 (14$\text{H}$,3$\text{H}$,9$\text{H}$,12$\text{H}$)-tetraones (mixed flavins) were prepared by the cyclization of 1,5-dihydro-8-[N-alkyl-N-(5-nitrouracil-6-yl)-amino-5-deazaflavins with Vilsmeier reagent. The mixed flavins oxidized alcohol under neutral condition in sunlight and a remarkable autorecycling was observed.     

Steroidal antifeedants from the dorid nudibranch Aldisasanguineacooperi

Two steroids, 3-oxo-chol-4-ene-24-oic acid ($\text{2}$) andi ts unsaturated analog $\text{4}$ have been isolated from the dorid nudibranch $\text{Aldisa}$$\text{sanguinea}$$\text{cooperi}$, and the acid $\text{2}$ has been shown to have antifeedant properties.     

Palladium catalysed synthesis of N and S heterocyclic esters

Palladium catalysed alkoxycarbonylation of heterocyclic halides affords a simple and versatile synthesis of both $\text{N}$ and $\text{S}$ heterocyclic esters where a range of catalysts have been studied and a method to employ inexpensive inorganic bases has been found.     

Structures of simarinolide and guanepolide (x-ray analysis), new quassinoids from Simaba cf orinocensis

Simarinolide $\text{4a}$ and Guanepolide $\text{5a}$ are new quassinoids with a C₂₅ basic skeleton isolated from a member of the French Guyanan Simaroubaceae, Simaba cf orinocensis H.B.K. The structure $\text{4a}$ was established by spectral means and that of $\text{5a}$ by X-ray diffraction analysis. The previously known simarolide $\text{1}$ was also isolated.     

Methods for stereospecific synthesis of cis or trans hydrindanones

Methods are described for the stereospecific conversion of hydrindenone 3 either to the corresponding $\text{trans}$ fused or $\text{cis}$ fused hydrindanone (1 or 2, respectively.)     

Synthesis of N-benzoyl-L-daunosamine from D-threonine

The synthesis of N-benzoyl-$\text{L}$-daunosamine (14) from the C₄$\text{threo}$ aldehyde (2b), prepared from $\text{D}$-threonine, through the intermediacy of the C₇ adduct (7a) is reported     

Rotational isomerism between the E and Z forms of o-substituted benzo-N-methyl hydroxamic acids in strong acid

The $\text{E}$∠$\text{Z}$ equilibrium of the cations of benzo hydroxamic acids, in mineral acid, was studied utilizing ¹H NMR spectroscopy, NOEDS and MNDO claculations     

A stereocontrolled synthesis of Z and E terminal dienes from pinacol E-1-trimethylsilyl-1-propene-3-boronate

Pinacol $\text{E}$-1-trimethylsilyl-1-propene-3-boronate reacts with aldehydes to form (±)-($\text{R}$*,$\text{S}$*)-3-trimethylsilyl-4-hydroxy-1-alkenes, which can be deoxysilylated stereoselectively to either 98% $\text{Z}$ or 99% $\text{E}$ 1,3-dienes, including the separate components of the red bollworm moth pheromone.     

Synthesis of (1s,5r)-karahana ether and (1s,5r)-karahana lactone,the optically active forms of unique monoterpenes wit

(1$\text{S}$,5$\text{R}$)-(-)-Karahana ether (8,8-dimethyl-2-methylene-6-oxabi-cyclo[ 3.2.1]octane) and (1$\text{S}$,5$\text{R}$)-(-)-karahana lactone (8,8-dimethyl-2-methylene-6-oxabicyclo [3.2.1]octan-7-one) were synthesized from ($\text{S}$)-3-hydroxy-2,2-dimethylcyclo-hexanone. The natural karahana lactone was shown to be almost racemic ($\text{ca}$. 1.3 % e.e.).     

Synthesis of N-benzoyl L- and D-2,3,6-trideoxy-3-aminoxylo-hexose from non-carbohydrate precursors

The enantiomeric alcohols ($\text{2}$) and ($\text{11}$), obtained from (2$\text{R}$,3$\text{R}$) tartaric acid and, respectively, $\text{L}$-threonine, have been used to construct the C₆, enantiomeric deoxy amino sugar derivatives ($\text{7}$) and ($\text{12}$)     

Highly substituted chromanols from cultures of aspergillusduricaulis

The new compounds $\text{1}$ – $\text{4}$ and $\text{8}$ have been isolated from cultures of $\text{Aspergillus}$$\text{duricaulis}$     

The sterepolides: new isolactaranes from stereumpurpureum

Sterepolide and dihydrosterepolide, new sesquiterpenes isolated from the fungus $\text{Stereum}$$\text{purpureum}$, are assigned structures $\text{4}$ and $\text{7}$, respectively. The assignments are based mainly on spectroscopic studies and similarities to isolactarorufin ($\text{5}$). A possible mode of biogenesis of these isolactarane type sesquiterpenes is discussed.     

Isolation and structures of trans-laurencenyne,a possible precursor of the C15 halogenated cyclic ethers,and trans-neolaurencenyne from laurencia okamurai

Isolation and structural elucidation of two new acetylenic polyenes, $\text{trans}$-laurencenyne $\text{1}$ and $\text{trans}$-neolaurencenyne $\text{2}$ from the marine red alga $\text{Laurencia okamurai}$ were carried out, the former compound $\text{1}$ very recently being proposed to be a biosynthetic precursor of the C₁₅ halogenated cyclic ethers, $\text{7}$ and $\text{8}$.     

A new polyether toxin from Gymnodiniumbreve Davis

A new ichthyotoxic toxin was isolated from the unialgal culture of the deleterious Florida red tide organism, $\text{Gymnodinium}$$\text{breve}$ Davis (Syn. $\text{Ptychodiscus}$$\text{brevis}$), and its structure was elucidated.