Masakazu Sono

Eremophilane-type sesquiterpenes from fresh rhizomes of Petasites japonicus

Abstract Ten new eremophilane-type sesquiterpene lactones, eremopetasitenins A1, A2, B1, B2, C1, C2, C3, D1, D2, and D3, sulphoxide bearing lactone, eremopetasinsulphoxide, and two methoxyl derivatives, as well as seven previously known sesquiterpenes have been isolated from fresh rhizomes of Petasites japonicus and their structures determined by spectroscopic techniques. Epoxyeremophilanolides, eremopetasitenins A1, A2, B1, and B2, are proposed to be important biogenetic intermediates.

Chemical and genetic diversity of Ligularia vellerea in Yunnan, China

Intra-specific diversity in Liularia vellerea growing in the northwestern to central Yunnan province of China was studied by chemical and genetic approaches. Samples collected in the Jianchuan, Lijiang, and Zhongdian areas contained 6,15-dioxygenated furanoeremophilanes as their major components (type A); whereas samples from the Luguhu area accumulated 1,6-dioxygenated furanoeremophilanes (type B); a sample from near Kunming, however, contained 6,15-dioxygenated eremophilanolides (type C). 11 beta H- and 11 alpha H-6 beta-angeloyloxy-15-carboxyeremophil-7-en-12,8-olides (eremofarfugins D and E) were also isolated and their structures were determined. A correlation between the composition and the DNA sequence was observed in the ITSs.

Functionalisation including fluorination of caffeine, guanosine tetraacetate, and uridine triacetate using electrochemical oxidation

Abstract The title compounds have been subjected to electrochemical oxidation with Et 3 N-3HF as an electrolyte. Caffeine afforded 8-fluorocaffeine as a sole product in 43% yield. Guanosine tetraacetate and uridine triacetate gave the fluorinated compounds in 7.3 and 4.8 % yield, respectively. Similar electrochemical oxidation of caffeine with methanol, KCl or KCN yielded 8-methoxycaffeine, 8-chlorocaffeine, or 8-cyanocaffeine, respectively.

NOVEL EPOXYEREMOPHILANOLIDES, EREMOPETASITENINS A1, A2, B1, AND B2, FROM PETASITES JAPONICUS

Abstract Eremopetasitenins A1, A2, B1, and B2 have been isolated from the fresh rhizomes of Petasites japonicus and their structures determined by spectroscopic methods to have eremophilane skeletons with epoxylactones.

Cyclization into perhydronaphthalenones using samarium diiodide

Samarium(II) diiodide has been employed to promote the intramolecular cyclization reactions of aldehydes or ketones onto α,β-unsaturated ketones. The cyclization reactions described herein provide a general approach to the syntheses of perhydronaphthalenones with a cis-relationship between the OH at C-5 and the proton or methyl group at C-4a with good diastereoselectivity under mild reaction conditions.

Eremofarfugin A and eremopetasitenin B3, two new eremophilanolides from Farfugium japonicum

Abstract Two new eremophilanolides, eremofarfugin A and eremopetasitenin B 3 , have been isolated from the methanol extract of fresh rhizomes of Farfugium japonicum (Compositae) and their structures have been determined on the basis of high resolution 2D NMR analysis.

Four alkaloids, lucidine B, oxolucidine A, lucidine A, and lucidulinone from Lycopodium lucidulum.

The structures of four alkaloids extracted from Lycopodium lucidulum (Lycopodiaceae) were established by X-ray and 2D NMR spectroscopic analyses. The dihydro-derivative of oxolucidine A, which was obtained by NaBH4 reduction of oxolucidine A, was treated with p-bromobenzoyl chloride to afford crystals, whose X-ray crystallographic analysis established the stereostructure, including the absolute configuration. The 2D NMR spectra of tetrahydrodeoxylucidine B were fully analyzed to establish the full structure of lucidine B, and the hitherto unknown stereochemistry at the C-14 position was established as beta-H. The structure of a new alkaloid, lucidulinone, was determined by spectroscopic analysis to be luciduline lactam.

First direct evidence of radical intermediates in samarium diiodide induced cyclization by ESR spectra.

The mechanism of samarium diiodide (SmI(2))-induced cyclization of α,β-unsaturated esters and ketones to bicyclic compounds was examined using ESR spectroscopy. This is the first report of direct evidence of the radical intermediates in the SmI(2) reaction. The preferential reduction of the α,β-unsaturated carbonyl part in some substrates should be recognized as a main route.

Synthesis of liverwort sesquiterpene (−)-isocuparene (herbertene) via a Diels-Alder reaction using phenylethylamine as chiral auxiliary

Abstract The imine of 2-methylcyclopentanone with ( S )-(−)-phenylethylamine was subjected to reaction with methyl propiolate and the product was transformed into (−)-isocuparene by use of a Diels-Alder reaction to construct the aromatic ring.

Total synthesis of coronafacic acid through 6-endo-trig mode intramolecular cyclization of an enone-aldehyde to a hydrindanone using samarium(II) iodide

Abstract Coronafacic acid has been synthesized from a hydrindanone prepared by a 6- endo - trig mode cyclization reaction of the enone-aldehyde with samarium(II) iodide. The stereochemistry of the hydrindanone was controlled by the coordinated samarium species resulting in cis in respect of the hydroxyl group at C-4 and the juncture proton at C-3a.