Stereocontrolled (E,Z and erythro, threo) synthesis of ⊙-hydroxyallylic sulphides

All four isomers of substituted 3-alkylthio-4-hydroxybutenes have been synthesised: both the geometry of the double bond and the relative stereochemistry of the two chiral centres are controlled.     

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.     

[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.     

Die Schwingungsspektren der isomeren Komplexe N,N′-Bis(dimethylgallium)-cis- und trans-N,N′-dimethyloxamideine kritische Analyse

Reaction of Ga(CH₃)₃ with N,N′-dimethyloxamide affords two isomeric N,N′-bis(dimethylgallium)-N,N′-dimethyloxamide complexes, characterized by crystal structure analysis as having cis-and trans-configuration with respect to the central oxamide CC bond and belonging to the point groups C_2v (cis) and C_2h (trans), respectively. Both isomers which are formed in varying ratio, depending upon the reaction conditions, have been isolated in pure form; their vibration spectra (IR/RE) are analyzed in detail in points of alternative behaviour, and are assigned in all bands, especially in the G-C and Ga-X frequency region. The assignment receives further confirmation from a comparison with the vibrational data of the homologous N,N′-bis(dimethylgallium)oxamide (cis/trans isomer mixture).     

A short synthesis of (s)-5-hydroxymethyl-(5h)-furan-2-one and derivatives from d-ribonolactone

We describe a short synthesis of ($\text{S}$)-5-hydroxymethyl-(5$\text{H}$-furan-2-one and some 5-O-derivatives, which are being used as key starting products for the synthesis of several antileukaemic lignan lactones, from $\text{D}$-ribonolactone.     

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 (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.).     

Syncarpurea,a novel metabolite from uvaria afzelii

The isolation and structure determination of syncarpurea (1), a novel urea from $\text{Uvaria afzelii}$ is reported.     

Brunfelsamidine: a novel convulsant from the medicinal plant brunfelsiagrandiflora

A convulsant isolated from $\text{Brunfelsia grandiflora}$ is identified as pyrrole-3-carbox-amidine.     

Aflavinine,a novel indole-mevalonate metabolite from tremorgen-producing aspergillusflavus species

The structure of aflavanine, a new diterpene indole from $\text{A}$. $\text{flavus}$, is presented.