Pyrolysis of homoadamant-3-ene

Pyrolysis of homoadamant-3-ene ($\text{5}$), generated from 1-adamantylcarbene ($\text{7}$), leads to the same three olefins ($\text{2}$, $\text{3}$, and $\text{4}$) that are produced from pyrolysis of 3-homoadamantyl acetate ($\text{1}$).     

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 of (±)-1-desoxy-2-lycorinone and of a possible trans-dihydro-lycoricidine precursor

En-route from the 5-aryl-3-hydroxy-4-nitro-cyclohexanones $\text{1}$ and $\text{2}$, readily available from poly-enolates and 3.4-methylenedioxy-w-nitro-styrene, to dihydro-lycoricidine $\text{3}$ and to lycorine $\text{4}$, respectively, the title compounds $\text{9}$ and $\text{14}$ are prepared in few steps.     

Synthesis of the n-benzoyl derivatives of L-arabino,L-xylo and L-lyxo (L-vancosamine) isomers of 2,3,6-trideoxy-3-C-methyl-3-aminohexose from a non-carbohydrate precursor

The synthesis of the N-benzoyl derivatives of $\text{L}$-$\text{arabino}$ (10),$\text{L}$-$\text{xylo}$ (13) and $\text{L}$-$\text{lyxo}$ ($\text{L}$-vancosamine) (12) 2,3,6-trideoxy-3-$\text{C}$-methyl-3-aminohexose from the (2$\text{S}$,3$\text{R}$) diol (1) prepared in fermenting bakers' yeast from α-methylcinnamaldehyde and acetaldehyde is reported     

Molecular rearrangements of 5-azido substituted 1,2,3-triazoles

5-Azido-4-methoxycarbonyl-1-phenyl-1,2,3-triazole ($\text{8a}$) and its phenyl substituted derivatives $\text{8b}$,$\text{c}$ rearrange at 60–80°C to give tetrazolyldiazoacetates $\text{9}$, which have been isolated. When the reactions are allowed to go to completion, products derived from the diazo compounds are obtained; i.e. norcaradienes ($\text{10}$) from benzene solutions and imidazotetrazoles ($\text{12}$) from nitrite solutions. The latter decompose photochemically into diazacyclopentadienonimines ($\text{13}$). A kinetic study of the rearrangement $\text{8}$ → $\text{9}$ has been carried out and the mechanism (Scheme VI) is discussed in comparison with the Dimroth rearrangement.     

The mechanism of biomolecular methyl transfer in a methyl aminoalkanesulfonate. application of 18o isotope shifts in 13cmr spectra of sulfonic esters.

¹³Cmr spectra show complete absence of scrambling of an ¹⁸O label in $\text{1}$$\text{a}$ recovered after partial conversion to $\text{2}$$\text{a}$ thereby precluding an $\text{0}$-methylation mechanism for the bimolecular formation of $\text{2}$$\text{a}$ from $\text{1}$$\text{a}$.     

Eugenol and safrole as starting materials for the synthesis of 3-alkyl muconic acid mono and dimethyl esters and 4,4-dialkyl butenolides

Compounds $\text{1b-e}$ and $\text{2b-d}$ prepared from eugenol ($\text{1a}$) and safrole ($\text{2a}$) respectively were submitted to ozonation in methanol at 0°C. The 3-alkyl muconic acid dimethyl esters $\text{4b-e}$ were produced from $\text{1b-e}$ (～ 45%), while starting from $\text{2b-d}$ the 3-alkyl muconic acid monomethyl esters $\text{6b-d}$ were obtained regiospecifically (～ 75%). These latter compounds were transformed (～ 85%) into the 4,4-dialkyl butenolides $\text{7b-d}$.     

Revision of the structure assigned to a monoterpene isolated from Piqueria trinervia

Unambiguous synthesis of 2-methyl-3-isopropenylanisole ($\text{1}$) and 2-isopropenyl-3-methylanisole ($\text{4}$) has led to revision, from ($\text{1}$) to ($\text{4}$), of the structure assigned to a monoterpene phenol ether isolated from $\text{Piqueria trinervia}$.     

Preparation of some highly halogenated derivative of furan

Direct chlorination of 2-(2H-hexafluoropropyl)-tetra- hydrofuran $\text{1}$ gave high yield of 2-(2-chlorohexafluoropropyl)- pentachloro-2,5-dihydrofuran $\text{2}$. Bromination of $\text{1}$ gave very complex mixture of products, from which three compounds, $\text{viz}$. 2-bromo-5-(2H-hexafluoropropyl)-furan $\text{3}$, 3-bromo-5-(2H-hexafluoropropyl)-furan $\text{4}$, and 2,4-dibromo-5-(2H-hexafluoropropyl)furan $\text{5}$ were isolated. Exchange fluorination of $\text{2}$ with dry KF at 240 – 300° led to a stepwise substitution of fluorines for chlorines to give mixtures of chloro-fluoro-2-(2-chlorohexafluoropropyl)-dihydrofurans $\text{7}$,$\text{8}$,$\text{9}$ and $\text{10}$, together with small amounts of 2-(2-chlorohexafluoropropyl)-3,4,5-trichlorofuran $\text{6}$.Exchange fluorination of 3,4-dihalo-2,2,5,5-tetrafluoro- 2,5-dihydrofurans $\text{11a}$ and $\text{11b}$ led to a substitution of fluorine for one vinylic halogen to give 3-halo-2,2,4,5,5-pentafluoro-2,5-dihydrofurans $\text{12a}$ and $\text{12b}$ in good yields.Compounds $\text{2}$ – $\text{12}$ were characterised by n.m.r., m.s., and i.r. spectroscopy and elemental analysis.     

Synthesis of optically active leukotriene (SRS-A) intermediates

In an approach to SRS-A and analogues thereof, the key (5$\text{S}$, 6$\text{S}$)-epoxy alcohol $\text{9}$ and its 6-epimer $\text{18}$ were prepared starting from $\text{D}$-araboascorbic acid and $\text{L}$-diethyl tartrate, respectively.     

Synthesis of erythrinin A,a naturally occurring pyranoisoflavone

Erythrinin A ($\text{10}$) has been synthesised by the oxidative rearrangement of dihydropyranochalcone $\text{1}$ with thallium(III) nitrate (TTN) in trimethyl orthoformate (TMOF) to the dimethyl acetal $\text{2}$, followed by cyclisation to $\text{3}$, demethylation to $\text{6}$ and dehydrogenation. Compound $\text{10}$ could also be obtained from chalcone $\text{4}$ on similar rearrangement followed by cyclisation, demethoxymethylation and dehydrogenation. In another route, chalcone $\text{7}$ was oxidatively rearranged with TTN in TMOF, to $\text{8}$ which on treatment with HCl yielded $\text{10}$.     

Stereospecific synthesis of (5E)-PGE2 by palladium-catalyzed decarboxylative 2-alkenylation of 2-alkenyloxycarbonylated cyclopentanone derivative

(5$\text{E}$)-Prostaglandin E₂ methyl ester was synthesized from ($\text{R}$)-4-$\text{t}$-butyldimethylsiloxy-2-cyclopentenone by $\text{in}$$\text{situ}$ 2-alkenyloxycarbonylation of the organocopper conjugate-addition adduct followed by intramolecular palladium-catalyzed decarboxylative 2-alkenylation. A ($\text{E}$)-2-butenylated cyclopentanone derivative was obtained from either 2-[($\text{E}$)- or ($\text{Z}$)-2-butenyloxy-carbonyl]cyclopentanone derivative under the similar reaction condition.     

Conversion of clavulanic acid into thiadeoxa nuclear analogues

1,4-Addition of sulphur nucleophiles to the diene ($\text{12}$) derived $\text{via}$ the pen-2-em ($\text{5}$) from clavulanic acid provides the thiadeoxa analogues ($\text{14}$–$\text{15}$). X-ray analysis of the ester ($\text{14}$) shows the thermodynamically stable isomers to have the same relative stereochemistry as clavulanic acid.     

The reactions of organolithium compounds with α,α-dibromoaldimines and of lithium amide with α-brominated aldimines

β-Bromoenamines $\text{4}$ and α-bromoaldehydes $\text{6}$ are synthesised from the ambident anions $\text{3}$ generated from either α-bromoaldimines $\text{1}$ or α,α-dibromoaldimines $\text{2}$.     

The total synthesis of d1-dihydrocallitrisin

Bromodiene $\text{2}$ is converted to $\text{dl}$-dihydrocallitrisin ($\text{1}$), a sesquiterpene lactone recently isolated from the heartwood of $\text{Callitris}$$\text{columellaris}$.     

Condensed cyclic and bridged-ring systems : part 12: A novel synthetic route to 4-p-methoxyphenyl-bicyclo[ 2.2.2 ]octan-2-ones and some bicyclo [ 3.2.1 ] octane derivatives by acid-catalyzed intramolecula

The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{5}$) and 4-$\text{p}$-methoxyphenylbicyclo [2.2.2] octan-2-one ($\text{6}$) from easily accessible starting materials. The carbinol $\text{20}$, derived from $\text{5}$, undergoes facile rearrangement leading to 1-$\text{p}$-methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene ($\text{22}$), which has been transformed to $\text{endo}$-1-$\text{p}$-methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one ($\text{25}$).     

Biomimetic reactions of germacrenes

The biomimetic reactions of epoxygermacrene-D ($\text{1}$) with basic alumina afforded three new interesting compounds ($\text{4}$, $\text{5}$, and $\text{6}$), two of which ($\text{4}$ and $\text{6}$) have the same carbon skeleton as that of periplanone-A ($\text{3}$), a sexual stimulant for the American cockroach. The remaining one ($\text{5}$) is a bicyclo[3.1.0]hexane derivative, from whch an axisonitrile-3 type compound ($\text{14}$) has been produced. Finally, preisocalamendiol ($\text{2}$) was also converted into $\text{6}$.     

Synthesis and NMR study of norbornane/norbornene-fused tetracyclic azetidinones

Tetracyclic azetidinones$\text{8}$,$\text{9}$ and $\text{12}$–$\text{17}$ were synthesized. In the cases of$\text{8}$ and$\text{9}$, the main component was isolated from the two-component product of the cycloaddition. The minor component was concentrated to give a mixture, from which a computer technique utilizing the known spectrum of the main component gave the proton resonance spectrum also of the minor component. Only one diastereomer could be isolated for the each of the analogues$\text{12}$–$\text{17}$. Reaction of the 1,3-oxazine $\text{3}$ with chloroacetyl chloride gave, besides the azetidinone $\text{12}$, the 1,3-oxazine [2,3-$\text{b}$]-1,3-oxazin-4-one derivative$\text{18}$. Configurations and conformations were determined by IR, ¹H and ¹³C NMR spectroscopy.     

Synthesis of streptococci phosphatidyl-α-diglucosyldiglyceride and related glycolipids : Application of the tetraisopropyldisiloxane-1,3-diyl (tips) protecting group in sugar chemistry. Part V

A short and convenient synthesis of phosphatidyl-α-diglucosyldiglyceride (i.e. compound $\text{8d}$) and two related Streptococci glycolipids (i.e. compounds $\text{6a}$ and $\text{6b}$) will be presented. 4',6'-Tetraisopropyl-disiloxane-1,3-diyl (TIPS) protected α-glucosyl diglyceride (i.e. compound $\text{2}$) turned out to be a suitable protected precursor. Thus, compound $\text{2}$ was selectively condensed with glucosyl bromide $\text{3}$ to afford $\text{4}$. Removal of the protecting groups from $\text{4}$ gave glycolipid $\text{6a}$. The “dynamic” properties of the TIPS pro- tecting group were utilized to convert 4',6'-TIPS protected $\text{4}$ into 3',4'- TIPS protected derivative $\text{5a}$. Compound $\text{5a}$ could then be condensed with either a stearoyl fatty acid or a phosphatidyl moiety to give the fully protected derivatives $\text{5c}$ and $\text{8a}$, respectively. Finally, removal of all the protecting groups from $\text{5c}$ and $\text{8a}$ afforded the glycolipid $\text{6b}$ and glycophospholipid $\text{8d}$, respectively.     

Reactivity of 1-cyclopropene-1-lactones dependent on the substitution degree

Reaction of the α-chloro lactone $\text{10}$ with KOtBu gives the butoxy lactones $\text{21}$ and $\text{22}$; the seven-membered derivative $\text{11}$ leads to $\text{23}$ as the only isolable product. Formation of the α-substitution product $\text{21}$ as well as the enhanced instability of the Intermediates $\text{12}$ and $\text{13}$ in comparison to their methyl substituted homologues $\text{5}$ and $\text{6}$ show the kinetical stabilization by a methyl group at C-2. Products derived from a cyclopropeno lactone of type $\text{A}$ could not be detected.