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Iridium(III)—salen complexes (I) catalyze the title reaction of 2-ethylbenzenesulfonyl azides to give five-membered sultams with high enantioselectivities.

One-step chemical conversion of flavanones into isoflavones by use of thallium trinitrate (TIN) is reported, and the mechanism of a 2,3-aryl migration in this reaction is discussed in relation to in vivo rearrangement process of flavanone precursors in the isoflavone biosynthesis.

The 9,10-dicynoanthracene (DCA)-sensitized photoreaction of 1,2-diarylcylopropanes 1a-d in nitrogen oxide (NO)-saturated CH 3 Cn afforded 3,5-diaryl-2-isoxazolines 2a-d in excellent yiels. The reaction of 1a-d with NOBF 4 or with a mixture of NO and O 2 in CH 3 CN also afforded 2a-d or 2a-b. These reactions proceed via the attack of NO on the radical cation of 1 which is formed by electron transfer from 1 to 1 DCA . or NO +

The construction of a carbon-selenium double bond was achieved by the reaction of acetal derivatives with bis(dimethylaluminum) selenide, and a variety of selenocarbonyl compounds containing selenoaldehydes, selenoformamides, and selenonesters were efficiently synthesized.

From the rhizome of Anemarrhena asphodeloides Bunge (Liliaceae), four new steroidal saponins named anemarrhenasaponins I-IV (1-4) were isolated, together with known saponins, timosaponin A-III (5), marcogenin diglycoside (6) and timosaponin B-II (7) and a xanthone C-glycoside, mangiferin. These saponins are coprostane type steroidal glycosides. Their structures were established on the basis of spectroscopic and chemical evidence.

The photochemical properties of 1,2-diarylcyclopropanes bearing an acetylphenyl group were studied by product analysis and laser flash photolysis. All cyclopropanes showed efficient cis−trans photoisomerization followed by inefficient isomerization to 1,3-diarylpropenes. All the products were unquenched by the addition of triplet quencher, 2-methyl-1,3-butadiene (ET ≃ 60 kcal mol-1), whereas molecular dioxygen gave oxygenated products. Triplet 1,3-biradicals generated from a short-lived acetophenone-like triplet (≲1 ns) were observed as intermediates in these reactions through nanosecond laser flash photolysis. Polar substituent effects on the lifetime of the 1,3-biradicals were small, except for a heavy atom effect in the case of Br. Spin−orbit coupling calculations on model 1,3-biradicals show a negligible effect on polar substituent and thus predict a negligible effect on the intersystem crossing rate. Conjugated biradicals in general now seem unlikely to show the “ionic character effect” on intersyste...

A novel family of mesoporous oxides of rare earth metals (Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were synthesized with specific surface areas of 253-348 m(2) g(-1) and pore diameters of 2.5-3.0 nm (see Scheme). The mesoporous solids and their surfactant mesophase precursors are paramagnetic and exhibit a magnetic anomaly due to the mesostructured atomic arrangement.

The effect of amines on the selective bromination of some β-substituted-2-butenoic esters is described. The bromination of methyl (Z)-4-t-butyldiphenylsilyloxy-3-methylbutenoate 2 in the presence of DIPEA (N, N-diisopropylethylamine) and the successive treatment of the obtained dibromide with potassium t-butoxide afford the desired Z bromide selectively. But the corresponding E bromide forms exclusively when 2, 6-di-t-butyl-4-methylpyridine is used in the bromination.

Drei- und siebengliedrige Ringe lieferte die Titelreaktion von terminalen Olefinen mit Vinyldiazolacton als Carbenquelle (siehe Beispiel). Die Dreiringe entstanden mit hoher trans-Selektivitat, und bei 1,3-Dienen wurde hoch regioselektiv die terminale Doppelbindung cyclopropaniert. Hydrolyse dieser Lactone und Cope-Umlagerung fuhrten mit hoher Enantioselektivitat zu den Siebenringen.

Two new compounds, 8'-phospho derivatives of amicoumacins A and B, were isolated from the culture broth of a strain of Bacillus pumilus together with amicoumacins A and B. Their structures were elucidated on the basis of spectroscopic methods and alkaline phosphatase treatments. Comparison of the antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA) of these compounds suggested that C-8' hydroxyl and C-12' amide group of amicoumacin A played a critical role for anti-MRSA activity.

A novel shunt product, actinoperylone, has been isolated from a deletion mutant of the actVA-ORF5 and ORF6 genes involved in the biosynthesis of a benzoisochromanequinone (BIQ) antibiotic actinorhodin (ACT) in Streptomyces coelicolor A3(2). Spectroscopic analysis revealed its perylenequinone-type skeleton with the four chiral centers, obviously derived from the dimerization of an ACT intermediate. The structure of actinoperylone indicates the essential role of ActVA-ORF5 in the oxygen introduction at C-6, which is common to the formation of BIQ chromophore. The present results also agree with the distribution of the actVA-ORF5 homologues in all known BIQ biosynthetic clusters in streptomycetes.

Tertiary cyclopropanol compounds react with a catalytic amount of vanadyl acetylacetonate in the presence of oxygen affording β-hydroxyketones and β-diketones. For 3-substituted-bicyclo[4.1.0]alkanols, peroxides are obtained, as are the β-hydroxyketones. Conversely, 2-ethoxycarbonylcyclopropyl silyl ethers produce ethyl γ-oxocarboxylate derivatives given the same reaction conditions.

A series of novel 26-substituted milbemycin A4 derivatives was synthesized from 5-O-t-butyldimethylsilyl-26-hydroxymilbemycin A4 prepared by selenium dioxide oxidation of 5-O-t-butyldimethylsilyl-milbemycin A4. Their acaricidal activities were assessed against the organophosphorus-sensitive two-spotted spider mite (Tetranychus urticae) on the primary leaves of cowpea plants (Vigna sinesis Savi species) by spraying.

Triphenylgermane easily adds to acetylenes or terminal olefins in the presence of Et3B to give alkenyltriphenylgermane or alkyltriphenylgermane respectively under excellent control of regio- and stereoselectivities. While Et3B catalyzed addition of Ph3GeH to 1-dodecyne at −78 °C affords (Z)-1-triphenygermyl-1-dodecene exclusively, the addition of Ph3GeH at 60 °C provides (E)-1-triphenylgermyl-1-dodecene as a single product. The triphenylgermyl radical is also effective to isomerize Z-olefins into their thermodynamically more stable E-isomers.

Apres hydrogenolyse des produits sur Pd/C, obtention des 1,2-threo-2,3-erythro-2-alkyl-1,3-diaryl-1,3-diols correspondants. Mecanisme de la photoreaction

Treatment of terminal or internal acetylenes bearing a variety of substituents with perfluoroalkyl iodides in the presence of a catalytic amount of triethylborane provides the corresponding perfluoroalkenes in good to excellent yields. The addition of perfluoroalkyl iodides to olefins is also described.

Treatment of terminal acetylenes (R 1 CCH) with secondary or tertiary alkyl iodides (R 2 I) in the presence of triethylborane provides the corresponding alkenyl iodides (R 1 C(I)CHR 2 ) in good yields.