Judit Halász

Structure of a Novel Triterpene Saponin from Gypsophila capillaris (Forssk.)

A novel triterpenoid saponin was isolated from Gypsophila capillaris (Forssk.) and its structure and conformational behaviour were investigated by one‐ and two‐dimensional 1H and 13C NMR spectroscopy.

Stereoselective epoxidation of 2-arylidene-1-indanones and 2-arylidene-1-benzosuberones

SummaryOxidation of the (E) and (Z) isomers of 2-arylidene-1-indanones (1) and 2-arylidene-1-benzosuberones (4) by alkaline hydrogen peroxide (methodi) afforded the spiroepoxidestrans-2a–g andtrans-5a–g from both isomers as sole products in high yields. On the other hand, dimethyldioxirane epoxidation(methodii) of the (E) isomers1a–g and4a–g gave the correspondingtrans spiroepoxides in good yields, whereas the (Z) isomers1a,c,e and4a,c,e led to thecis spiroepoxides in moderate yields. Dimethyldioxirane oxidation (methodii) of (Z)-1c and (Z)-4c,e gave diones3c and6c,e as by-products as well. Epoxidation of (Z)-1a,c,e and (Z)-4a,c,e bym-chloroperoxybenzoic acid (methodiii) resulted inca. 6:1 mixtures ofcis-2a,c,e andtrans-2a,c,e orcis-5a,c,e andtrans-5a,c,e spiroepoxides.ZusammenfassungOxidation der (E)- und (Z)-Isomeren von 2-Aryliden-1-indanonen (1) und 2-Aryliden-1-benzosuberonen (4) mit alkalischem Wasserstoffperoxyd (Methodei) liefert aus beiden Isomeren die Spiroepoxidetrans-2a–g undtrans-5a–g als einzige Produkte. Epoxidierung der (E)-Isomeren1a–g und4a–g mit Dimethyldioxiran (Methodeii) ergab die entsprechendentrans-Spiroepoxide in sehr guten Ausbeuten, während die (Z)-Isomeren1a,c,e und4a,c,e diecis-Spiroepoxide in nur mäßiger Ausbeute liefern. Oxidation von (Z)-1c und (Z)-4c,e mit Dimethyldioxiran (Methodeii) ergab die Dione3c und6c,e sowie einige Nebenprodukte. Wurden (Z)-1a,c,e und (Z)-4a,c,e einer Epoxidation mitm-Chlorperbenzoesäure (Methodeiii) unterworfen, entstanden 6:1-Gemische der Spiroepoxidecis-2a,c,e undtrans-2a,c,e odercis-5a,c,e undtrans-5a,c,e.

Synthesis of 2,2-dimethylbenzoxazepinones by the Beckmann rearrangement of 2,2-dimethyl-4-chromanone oximes

2,3-Dihydro-2,2-dimethyl-1,4-benzoxazepin-5(4H)-ones and 2,3-dihydro-2,2,6-trimethyl-1,5-benzoxazepin-4(5H)-ones have been synthesized by the Beckmann rearrangement of 2,2-dimethyl-4-chromanone oximes

Synthesis and stereochemistry of the epoxides of 2-arylmethylidene-1-tetralones

Oxidation of both the E and Z isomers of the 2-arylmethylidene-l-tetralones 1 by alkaline hydrogen peroxide afforded the spiroepoxides trans-2a–g as sole products in high yields. In contrast, the dimethyldioxirane epoxidation of the E isomers la–g gave the corresponding trans spiroepoxides in good yields, while the Z isomers 1a,c,e yielded the respective cis spiroepoxides in moderate yields. Epoxidation of (Z)-1a,c,e by m-chloroperoxybenzoic acid yielded ca. 6 : 1 mixtures of cis-2a,c,e and trans-2a,c,e spiroepoxides. Separation of the isomeric epoxides was achieved by silica gel chromatography and their structures, relative configurations and stereochemistry were elucidated by NMR spectroscopy.

Conformational analysis of 2,3-dihydro-2,2-dimethyl-1,4-benzoxazepines and their 1,5-isomers

SummaryConformational analysis of 2,3-dihydro-2,2-dimethyl-1,4-benzoxazepines (1,3,5, and7) and their 1,5-isomers (2,4, and6) was performed by temperature dependent NMR measurements. The effect of substituents on the ring inversion was studied. The results obtained were corroborated by AMl calculations.ZusammenfassungDie Konformation von 2,3-Dihydro-2,2-dimethyl-1,4-benzoxazepinen (1,3,5 und7) und ihren 1,5-Isomeren (2,4 und6) wurde mittels temperaturabhängiger NMR-Spektroskopie untersucht. Der Einfluß von Substituenten auf die Ringinversion wird diskutiert. Die erhaltenen Resultate werden durch AMl-Rechnungen bestätigit.

UV-induced isomerisation and ring transformation of (E)-3-arylidene-1-thiochromanones and -1-thioflavanones

Depending on the substituent of the arylidene moiety, photoisomerisation of (E)-3-arylidence-1-thiochroman-4-ones 1 and 3 afforded either the expected (Z)-1 and (Z)-3 isomers or the products (2d,e and 4c,d) of an unprecedented phototransformation.

Structure elucidation of the oxidation products of 2-arylidene-1-indanones and 2-arylidene-1-benzosuberones

The relative configuration and stereochemistry of spiroepoxides prepared by dimethyldioxirane, alkaline hydro‐gen peroxide and m‐chloroperoxybenzoic acid and of dione by‐products were elucidated by various 1H and 13C NMR methods.

Synthesis and stereochemistry of 8-methyl-5-nitro-1-octalones

SummaryBase catalyzedMichael addition of 5-nitropentan-2-one ethylene ketal (1) and cyclohex-2-enone (2), subsequent deprotection, and intramolecular aldol condensation yields the 8-methyl-5-nitro-1-octalone isomers (5a,b). The structure, relative configuration, and conformation of5a and5b were elucidated utilizing the results of1H and13C NMR investigationsZusammenfassungBasenkatalysierteMichael-Addition von 5-Nitropentan-2-on-ethylenketal (1) und Cyclohex-2-enon (2), anschließende Entfernung der Schutzgruppe und darauffolgende Aldolkondensation liefert isomer 8-Methyl-5-nitro-1-octalone (5a,b). Struktur, relative Konfiguration und Konformation von5a und5b wurden mittels1H- und13C-NMR-Spektroskopie aufgeklärt.

Dioxirane oxidation of benzopyrans, benzothiopyrans, and related compounds

Dioxiranes are shown to be powerful and convenient oxidation agents for benzopyrans, benzothiopyrans, and α, β-unsaturated ketones.