Formal total synthesis of β-pipitzol

(±)-$\text{O}$-methylperezone ($\text{1b}$) was obtained by selective oxidative demethylation of (±)-leucoperezone trimethyl ether ($\text{4a}$). Compound ($\text{4a}$) was prepared by condensation of 2,3,5-trimethoxytoluene ($\text{5e}$) with 6-methyl-5-hepten-2-one, followed by reductive removal of the tertiary alcohol. The aromatic precursor $\text{5e}$ was prepared in four steps from 2,3-dimethoxytoluene ($\text{5a}$) and, alternatively, in three steps from 5-bromoveratraldehyde ($\text{6a}$). Racemic $\text{1b}$ and $\text{4a}$ were directly compared with the optically active molecules prepared from natural R(-)-perezone ($\text{1a}$).     

Synthesis and absolute configuration of +-lineatin,the pheromone of trypodendronlineatum

A new synthesis of (±), (+)- and (-)-lineatin (3,3,7-trimethyl-2, 9-dioxatricyclo [3.3.1.0^4,7] nonane, $\text{1}$) was achieved. The stereochemistry of (+)-lineatin was established as 1$\text{R}$, 4$\text{S}$, 5$\text{R}$, 7$\text{R}$ by an X-ray crystallographic analysis of an intermediate $\text{1}$$\text{5}$.     

Structure and synthesis of reductiline,a novel metabolite from a variant of streptomyces orientalis

The structure of reductiline, a metabolite of a variant of $\text{Streptomyces orientalis}$ was elucidated as ($\text{1}$) based on chemical and spectroscopic evidence. Transformation of an antitumor antibiotic reductiomycin ($\text{2}$) into reductiline ($\text{1}$) was carried out. Synthesis of reductiline ($\text{1}$) was achieved starting from β-cyanopropionaldehyde dimethylacetal.     

Facile syntheses of 2,4,6-cycloheptatrienyl ketones

The synthesis of the 2,4,6-cycloheptatrienyl ketones $\text{1a}$–$\text{1e}$ by two alternative routes is reported: Route 1): The adducts $\text{3a–c}$ from the phenyl(trimethylsiloxy)-acetonitriles $\text{2a–c}$, known as “umpolung” reagents, and tropylium tetrafluoroborate are cleaved by triethylammonium fluoride to form the aromatic cycloheptatrienyl ketones $\text{1a}$–$\text{1c}$. Route 2): the phenyl, methyl, and cyclopropyl ketone ($\text{1a}$, $\text{1d}$, $\text{1e}$) are prepared by treatment of the acid chloride $\text{7}$ with the corresponding organomanganese iodides RMnI ($\text{8a}$, $\text{8d}$, $\text{8e}$). The Fe-catalyzed coupling reaction of the acid chloride $\text{7}$ with a Grignard reagent was also used for the preparation of ketone $\text{1b}$.     

A facile synthesis of (±)-sesbanine via γ-addition of ketene silyl acetal with quaternized methyl nicotinate

Total synthesis of (±)-sesbanine ($\text{1}$) was carried out using γ-addition of ketene silyl acetal of methyl 3-cyclopentenecarboxylate to quaternized methyl nicotinate. The resulting 1,4-dihydropyridine ($\text{7}$) was oxidized with DDQ to give 4-substituted nicotinate ($\text{2}$) and $\text{2}$ was converted to alcohol ($\text{8}$) by stereoselective oxymercuration followed by treatment with ammonia to give $\text{1}$.     

Photochemical studies. Irradiation induced transformations of 1,2-dihydrophthalides

The photochemical behavior of $\text{cis}$-1,2-dihydrophthalide ($\text{1}$) and its 1,2-trimethylene derivative ($\text{4}$) was studied. Besides bicyclo[2.2.0]hexene formation in both cases, ($\text{1}$) transforms into its $\text{trans}$ isomer ($\text{3}$) whereas ($\text{4}$) undergoes a 1,2-shift to ($\text{7}$).     

Biogenetic-type synthesis of (±)-dictyopterene A,an odoriferous substance obtained from brown seaweeds, Dictyopteris

Biogenetic-type synthesis of (±)-dictyopterene A ($\text{1}$) was achieved employing 1,$\text{cis}$-5-undecadien-3-ol ($\text{2}$) postulated to be a biosynthetic intermediate of $\text{1}$: this synthesis means that transformation of dictyoprolene ($\text{4}$) into dictyopterene A ($\text{1}$) was formally made.     

New highly strained bridgehead imines, 2-azaadamant-1-ene and 4-azaprotoadamant-3-ene

An azaanalog of adamantene, 2-azaadamant-1-ene ($\text{1}$) and 4-azaprotoadamant-3-ene ($\text{7}$) were generated in the nonstatistical ratio via photolysis of 3-azidonoradamantane ($\text{2}$). The highly strained $\text{1}$ and $\text{7}$ could not be isolable but were trapped by MeOH. Acidolysis of $\text{2}$ was also reported, and discussed in comparison with the photolysis.     

Chiroptical studies of labile or difficult to resolve molecules generated by chiral laser photochemistry.1. (1S,5R-1-methoxybicyclo[3.2.0] hepta-3,6-dien-2-one

The optical activity of (1$\text{S}$,5$\text{R}$-1-methoxybicyclo[3.2.0]hepta-3,6-dien-2-one ($\text{1}$) is determined by partial photoresolution of the racemate with circularly polarized laser light; although a rearranged, optically active product was also formed, isolation of the $\text{1}$ enantiomers was note required.     

Synthesis of (2S,3R,1'R)-stegobinone,the pheromone of the drugstore beetle,with stereocontrol at C-2 and C-1'

(2$\text{S}$,3$\text{R}$,1'$\text{R}$)-Stegobinone [2,3-dihydro-2,3,5-trimethyl-6-(1'-methyl-2'-oxobutyl)-4H-pyran-4-one], the pheromone of $\text{Stegobium}$ $\text{paniceum}$ L., was synthesized with stereocontrol at C-2 and C-1' starting from ethyl ($\text{R}$)-3-hydroxybutanoate and methyl ($\text{R}$)-3-hydroxy-2-methylpropanoate. The dihydro-γ-pyrone ring of the pheromone was constructed by an intramolecular acylation followed by acid-catalyzed cyclization.     

The resolution of racemic 2-alkyl-1-aminocyclopropane-1-carboxylic acids

Practical procedures for the resolution of racemic modification of (1$\text{R}$, 2$\text{S}$)-and (1$\text{S}$, 2$\text{R}$)-1-amino-2-ethylcyclopropane-1-carboxylic acid $\text{1a}$,$\text{b}$,(1$\text{R}$, 2$\text{S}$)- and (1$\text{S}$, 2$\text{R}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{2a}$,$\text{b}$, and (1$\text{R}$, 2$\text{R}$)- and (1$\text{S}$, 2$\text{S}$)-1-amino-2-methylcyclopropane-1-carboxylic acid $\text{3a}$,$\text{b}$ are described; the structures as $\text{1a}$,$\text{2a}$, and $\text{3a}$ were confirmed by X-ray-crystallographic methods.     

Photooxygenation of bicyclopropylidene

Upon photooxidation bicyclopropylidene ($\text{1}$) yields spiro[2.3]hexan-4-one ($\text{4}$) and 7-oxatrispiro[2.0.2.1]heptane ($\text{6}$). The formation of these is rationalized. Authentic $\text{6}$ was prepared by epoxidation of $\text{1}$, and $\text{4}$ by isomerization of $\text{6}$.     

Generation of an active acyl species from stable 1-methyl-2-acyl-1h-imidazoles

1-Methyl-2-(1′-cyano-1′-trimethylsilyloxy)alkyl-1H-imidazoles ($\text{2}$) were easily prepared from the corresponding stable carbonyl compounds, 1-methyl-2-acyl- ¹H-imidazoles ($\text{1}$). When the quarternary salts of $\text{2}$ were treated with various nucleophiles, reactive acyl species, which was presumed to be acylcyanide ($\text{12}$), was generated in situ under CC bond fission to result in producing the corresponding acylated compounds ($\text{5}$–$\text{10}$) in good yields.     

Stereoselective olefinic cyclization assisted by the selenyl group — biogenetic-type synthesis of caparrapi oxide

The acid catalysed cyclization of β-hydroxy selenide ($\text{4}$), which was prepared from nerolidol ($\text{1}$) $\text{via}$ the epoxide ($\text{3}$), was carried out to give bicyclic ether ($\text{5}$) directly which was further transformed into caparrapl oxide ($\text{6}$).     

The synthesis of cis- and trans-1,2-dibromocyclopropane

A preparative route to cis- and trans-1,2-dibromocyclopropane ($\text{1}$) was developed via the Hunsdiecker reaction of silver cyclopropane-1,2-dicarboxylate ($\text{2}$). Cis- and trans-$\text{2}$ gave the same ratio of cis- and trans-$\text{1}$ (1:3.2). The mechanism of this reaction is briefly discussed.     

New Phenyl propanoids having weak piscicidal action and the related compound: wutaiensol,wutaiensal, wutaialdehyde,and methyl demethoxywutaiensate

The structures of three new prenylphenyl propanoids, wutaiensol ($\text{1}$), wutaiensal ($\text{2}$), and methyl demethoxywutaiensate ($\text{4}$) were established by correlating with S-rutaretin methyl ether ($\text{9}$) or S-marmesin ($\text{24}$) by chemical means. The structure of wutaialdehyde ($\text{3}$), a related compound, was also established by total synthesis of the racemate and by correlating with $\text{1}$. Preliminary piscicidal test on these compounds disclosed that $\text{2}$ and $\text{4}$ are weakly bu distinctly positive.     

Efficient photochemical oxetane formation from 1-methyl-2,4,5-triphenylimidazole and benzophenones

In contrast to simple imidazoles, 1-methy1–2,4,5-triphenylimidazole ($\text{1}$) produced stable oxetane photoadducts $\text{3b}$ - $\text{e}$ with good efficiency upon irradiation in the presence of benzophenone derivatives $\text{2b}$ - $\text{e}$ in acetonitrile solution. Irradiation in the solid-phase was also studied. The oxetanes $\text{3b}$ - $\text{e}$ readily underwent cycloreversion by acid catalysis or by heating.     

4,6-Thioanhydro-hexopyranosides,synthesis and chemical behaviour of methyl 2-0-p-toluenesulfonyl-4,6-thioanhydro-α-d-gulopyranoside

Methyl 4-0-benzoyl-6-bromo-6-deoxy-α-D-glucopyranoside ($\text{1}$, Figure 1) was converted, via the corresponding ditosylate $\text{2}$, into methyl 2,3-di-0-p-toluenesulfonyl-4-0-benzoyl-6-S-acetyl-6-thio-α-D-glucopyranoside ($\text{3}$) by a selective nucleophilic displacement of 6-bromo-group with thioacetate. Unexpectedly, on treating the compound $\text{3}$ with an excess of sodium methoxide in benzene-methanol (1:1) at room temperature, methyl 2-0-p-toluenesulfonyl-4,6-thioanhydro-α-D-gulopyranoside ($\text{4}$) was obtained in a yield of 84%. In order to determine the structure of the relatively unstable oily product $\text{4}$, some stable crystalline derivatives ($\text{5}$, $\text{6}$ and $\text{7}$) were prepared. Detailed analysis of the ¹H-NMR-spectra (200 MHz) of $\text{6}$ and $\text{7}$ gave the conclusive evidence for the structure of $\text{4}$ A self-imposing mechanism of the clean and smooth transformation of $\text{3}$ to $\text{4}$ is proposed, involving: a) formation of $\text{9}$ (Figure 2) as a crucial intermediate and b) a highly regioselective epoxide opening in $\text{9}$ (at C-4) by an intramolecular nucleophilic attack of the mercaptide anion from C-6.