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.     

Addition conjuguee d'equivalents d'acyles aux cyclohexen-2 ones et a la Δ1(9) octalone-2: Synthese de dicetones 1–4.

The synthesis of 3-acetylcyclohexanones $\text{11}$, $\text{12}$, $\text{13}$ has been realized by conjugate addition of lithiated cyanohydrin ether $\text{1a}$ to 2-cyclohexenones $\text{2}$, $\text{3}$, $\text{4}$ in THF-HMPA, even if 3-substituted. 3-benzoylcyclohexanones $\text{14}$, $\text{15}$, $\text{16}$ are obtained from $\text{1b}$ and $\text{2}$, $\text{3}$, $\text{4}$ in THF with excellent yields.     

New tetrahydropyrans from a marine sponge

Two new tetrahydropyrans have been isolated from the sponge Haliclona sp. From chemical and spectroscopic evidence they are shown to be (1′$\text{R}$, 2$\text{S}$, 2″$\text{E}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromethyl)-2,5-dimethyl-6-(penta-2″,4″-dienyl)-tetrahydropyran and (1′$\text{R}$, 2$\text{S}$, 5$\text{R}$, 6$\text{R}$)-2-(1′-bromoethyl)-2,5-dimethyl-6-(pent-4″-enyl)-tetrahydropyran.     

Synthetic studies on β-lactam antibiotics. 18. Convenient,stereocontrolled synthesis of 3-methyl 7α-methoxy-1-oxacephems

Alcohols $\text{4}$ and $\text{8}$, prepared from $\text{3}$, underwent completely stereospecific etherification to give 1-oxacephams $\text{5}$ and $\text{10}$, which were converted into the 1-oxacephem nucleus $\text{1b}$ via $\text{6}$ and $\text{1c}$. Functionalization at C-3′ in $\text{6}$ and $\text{1c}$ was unsuccessful.     

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 $\text{1b}$.     

Pyridazines XXIV: Application of radicalic ethoxycarbonylation to the synthesis of pyridazine mono- and polycarboxylic acid esters

Reactivity of pyridazines $\text{1}$, $\text{2}$, $\text{3}$, $\text{16}$ towards ethoxycarbonylradical (generated by redox decomposition of oxyhydroperoxide of ethylpyruvate) was studied. Application of this type of homolytic substitution for synthesis of hitherto not accessible pyridazine carboxylic acid esters $\text{6}$, $\text{8}$, $\text{9}$, $\text{12}$, $\text{13}$, $\text{14}$, $\text{15}$, $\text{17}$ is demonstrated. In addition improved synthesis of diethyl 4,5-pyridazinedicarboxylate ($\text{5}$) is proposed.     

Substituted cyclononatetraenes and nonafulvenes

Reaction of $\text{cis}$,$\text{cis}$,$\text{cis}$,$\text{cis}$-[9]annulene anion ($\text{1}$) with electrophiles ($\text{2a}$-$\text{d}$) leads to substituted $\text{cis}$,$\text{cis}$,$\text{cis}$,$\text{cis}$-1,3,5,7-cyclononatetraenes ($\text{3a}$-$\text{d}$) which are precursors for the preparation of 10- and 10,10′-donor-substituted nonafulvenes (e.g. $\text{7b′}$$\text{e′}$). The influence of solvent and temperature on the ¹H-nmr spectra of the nonafulvenes $\text{7b′}$-$\text{h′}$ has been investigated.     

Synthesis of optically active pheromones with an epoxy ring, (+)-disparlure and the saltmarsh caterpillar moth pheromone [(Z,Z)-3,6-cis-1-9,10-epoxyheneicosadiene]

(+)-Disparlure $\text{2}$, and the saltmarsh caterpillar moth pheromone enantiomers $\text{1}$ were synthesized and the stereochemistry of the naturally occurring $\text{1}$ was shown to be 9$\text{S}$, 1O$\text{R}$.     

Isolation and structural elucidation of heliangolidin,a new sesquiterpene lactone from artemisia canariensis

A new heliangolide has been isolated from aerial parts of $\text{Artemisia canariensis}$, and identified as (6$\text{E}$,10$\text{Z}$)(3$\text{S}$,3a$\text{R}$,4$\text{S}$,lla$\text{R}$)-3a,5,8,11a--tetrahydro-4-acetoxy-3,6, 1O-trimethyl-2,9 (3$\text{H}$, 4$\text{H}$) -cyclodeca[b] furandione. The structural elucidation of the new compound, named heliangolidin, was carried out by spectral means (MS, IR, ¹H and ¹³C NMR, and two dimensional ¹H-¹³C chemical shift correlations) and X-ray diffraction analysis.     

Ciral synthons for the multistriatins

The readily-obtained carbohydrate α-enones $\text{2}$, $\text{5}$ and $\text{8}$ are converted into the four diastereomeric 2,4-di-C-methyl glycopyranosides $\text{4}$$\text{7}$,$\text{10}$,$\text{11}$, which are chiral synthons for the four multistriatins $\text{1a}$-$\text{1d}$.     

Action of tert-butyl azidoformate on the conjugate bases of 1,2,3,4-tetrahydro-9H-carbazole and other indole derivatives

tert-Butyl azidoformate ($\text{2}$) reacts with the conjugate bases of $\text{3a}$, $\text{7a}$, $\text{9}$ (R¹ = R² = CH₃), and $\text{9}$ (R¹ = CH₃, R² = H) to give products [$\text{4}$, $\text{8}$, $\text{12}$, and $\text{14}$, respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives.     

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}$.     

Completely stereoselective synthesis of all four stereoisomeric 1-carbamoyloxy-1,3-alkadienes via anti-diastereoselective homoaldol reaction from aldehydes and a single carbon-three-unit

Lithiation of both ($\text{Z}$)- and ($\text{E}$)-3-trimethylsilyl-2-propenyl $\text{N}$,$\text{N}$-diisopropyl carbamate 2 affords the (2$\text{E}$) -lithium compound 3. Aluminium- or titanium-mediated addition to aldehydes, 4 gives (1$\text{E}$)-(3$\text{R}$*4$\text{S}$*)-enol carbamates 7. A stereospecific Peterson elimination (borontriflouride- or base-mediated) introduces the second double bond either with (3$\text{E}$)- or with (3$\text{Z}$)-configuration. So just by reagent selection for each of the two steps, (1$\text{E}$,3$\text{E}$)-, (1$\text{E}$,3$\text{Z}$)-, (1$\text{Z}$,3$\text{E}$)-, or (1$\text{Z}$,3$\text{Z}$)- dienes 8 - 11, respectively, are prepared with stereoselectivities up to > 99.7%     

Efficient syntheses of naturally occurring 3,4-dihydroxyprolines: Electrophile-mediated lactonization of 2-amino-3-hydroxy-4-pentenoic acid derivatives

Stereospecific conversion of β-hydroxyallylglycine derivatives into (2$\text{S}$, 3$\text{R}$, 4$\text{R}$) 1 and (2$\text{S}$, 3$\text{S}$, 4$\text{S}$) 2 $\text{via}$ halo- or mercuri-lactonization has been described.     

Application of 2d-nmr spectroscopy in the structural determination of a new tobacco cembranoid

Proton-proton shift correlated 2D-NMR spectroscopy has been used to determine the structure of a new tobacco cembranoid as (1$\text{S}$,2$\text{E}$,4$\text{S}$,6$\text{R}$,7$\text{E}$)-4,6-dihy-droxy-2,7,12(20)-cembratrien-11-one (1). This assignment has been verified by chemical means.     

12-S-CIS conformationally locked retinoids: Thermal and photochemical interconversions leading to new geometric isomers

For 12-$\text{s}$-$\text{cis}$ locked retinal analogues, thermal equilibria are established between 11-$\text{cis}$, 13-$\text{cis}$-1c and 13-$\text{cis}$-2c and between 9-$\text{cis}$, 11-$\text{cis}$, 13-$\text{cis}$-1d and 9-$\text{cis}$, 13-$\text{cis}$-2d; a photoisomerization occurs to transform 2c to $\text{all}$-$\text{trans}$-2a and 2d to 9-$\text{cis}$-2b     

Stereochemistry of aplidiasphingosine as proposed by the asymmetric synthesis and 13c-nmr study of sphingosine relatives

The Sharpless asymmetric epoxidation was used for the synthesis of D-$\text{erythro}$-dihydrosphingosine triacetate and (2$\text{S}$, 3$\text{S}$, 5$\text{R}$)-2-acetamino-5,9-dimethyl-8-decene-1,3-diol, whose ¹³C-NMR study coupled with biogenetic consideration enabled us to propose (2$\text{1S}$, 3$\text{S}$, 5$\text{S}$,13$\text{R}$, 14$\text{S}$)-stereochemistry for aplidiasphingosine.     

Zur deprotonierung von chloromethyleniminiumchloriden

Deprotonation of chloromethyleniminium chlorides ($\text{1}$, $\text{13}$) leads to cis-trans-isomeres 1,2-diamino-1,2-dichloro-ethenes ($\text{3a}$, $\text{3b}$ resp. $\text{14a}$, $\text{14b}$); their reactivity is described.     

Synthesis and molecular structure of piplartine (=piperlongumine)

The structure of piplartine (=piperlongumine) was established as ($\text{1}$)-$\text{3}$-3',4',5'-trimethoxycinnamoyl-5,6-dihydro-2(1H)-pyridone ($\text{13}$) by synthesis and by an X-ray crystallographic analysis. Model condensation of ($\text{E}$)-3,4,5-trimethoxycinnamoyl chloride and crotonamide gave not the expected cinnamoylcrotonamide, but ($\text{1}$)-$\text{N}$-3', 4', 5' -trimethoxycinnamoyl-3-chlorobutyramide ($\text{12}$).     

Action de CF3 of sur des aziridines N-non substitutees

Aziridines $\text{I}$ react with trifluoromethyl hypofluorite at ? 40°C to produce mixtures of 1-(aziridine)carbonyl fluoride $\text{II}$ and 1-fluoroaziridine $\text{III}$, the proportions of which depend on steric effects. Several compounds $\text{II}$ react with starting materials to give 1, 1′-(carbonyl)bisaziridines $\text{IV}$. Most compounds $\text{II}$ and all compounds $\text{IV}$ are isolated. Chemical properties and ir and nmr data of $\text{II}$, $\text{III}$, $\text{IV}$ are described; the formation of an isocyanate and a substituted urea from a compound $\text{II}$ is observed. A mechanism for this reaction is suggested.