Natürliche Stilbene. Synthese von Polyhydroxystilbenäthern durch Wittig‐Reaktion

Abstract

Bisher schwer zugangliche Ather verschiedener naturlich vorkommender Polyhydroxystilbene werden mit 60-95 % Ausbeute durch Wittig-Reaktion erhalten.Pflanzeninhaltsstoffe mit Stilbenstruktur sind seit langem bekannt und in ihrer Konstitution geklart 1). Die uberwiegende Mehrzahl der naturlichen Stilbene besitzt Sauerstoff-Funktionen in Position 3 und 5 des einen aromatischen Ringes, wahrend der andere Ring entweder unsubstituiert ist oder bis zu drei Hydroxylgruppen in verschiedenen Stellungen enthalten kann. Die einfachen, niedrigsubstituierten Verbindungen sind uber die Stilbencarbonsauren durch Decarboxylierung dargestellt worden 1). Die entsprechende Synthese von Derivatenmit mehr als insgesamt drei freien Hydroxylgruppen, z. B. 3.4.3'.5'-Tetrahydroxy-stilben (Piceatannol), ergab nur sehr geringe Ausbeutenz), wahrend 2.4.3'.5'-Tetrahydroxy-stilben (Oxyresveratrol) synthetisch bisher uberhaupt noch nicht und einige seiner Vorstufen mit nur unbefriedigendem Ergebnis erhalten werden konnten. Uns interessierte im besonderen ein besserer Zugang zu Vorstufen des Oxyresveratrols, aus denen das in der thailandischen Volksmedizin als Anthelmintikum verwendete Hydroxystilben gewinnbar sein sollte.Der Tetramethylather des Oxyresveratrols wurde von Burnes und Gerber3) nach folgendem Verfahren synthetisiert : Umsetzung von 3.5-Dimethoxy-phenylacetonitril mit Resorcin und 1) G. BilleJc, Fortschritte der Chemie organischer Naturstoffe, Bd. 22,

Complexation of rhodium and platinum with P-functionalized calix[4]resorcines

“…3, Schemes 2 and 3). Similar reac tions were observed, e.g., in the synthesis of thienyla midophosphonium salts [22] or the thermal dealkyla tion of alkylamidophosphonium halides [23]. Moreover, similar reactions are favored by the destabilization of electron density in the macroring under the influence of Lewis acids and protic acids like compounds 1, 3, and 4.…”

Spasmolytic Effects, Mode of Action, and Structure−Activity Relationships of Stilbenoids from Nidema boothii,

“…14-16 Analogues 28 and 33 were synthesized by catalytic reduction of resveratrol and piceatannol, respectively. 17,19 Bibenzyls 23, 25, 28, and 29 were synthesized as previously described, and their spectral data were in agreement with those reported. [15][16][17][18][19] Compound 31 was newly synthesized, but it was previously isolated as a natural product from Dendrobium plicatile; 20 compounds 25, 21 27, 22 28, 23 29, 21 30, 24 and 33 25 have also been described as natural products, while bibenzyls 26 and 32 were previously obtained using catalytic reduction and methylation of rhapontigenin and O-methylbatatasin III, respectively.…”

“…17,19 Bibenzyls 23, 25, 28, and 29 were synthesized as previously described, and their spectral data were in agreement with those reported. [15][16][17][18][19] Compound 31 was newly synthesized, but it was previously isolated as a natural product from Dendrobium plicatile; 20 compounds 25, 21 27, 22 28, 23 29, 21 30, 24 and 33 25 have also been described as natural products, while bibenzyls 26 and 32 were previously obtained using catalytic reduction and methylation of rhapontigenin and O-methylbatatasin III, respectively. The 1 H NMR data of 26, 20 32, 24 obtained by the Wittig reaction in the present investigation, and 31, 26 as well as the complete spectral data for compounds 34 27,28 and 35, 29 were in agreement with those previously described.…”

“…[15][16][17][18][19] In all cases, the spectroscopic properties of the synthetic materials were identical to those described in the literature. [15][16][17][18][19] 4-Methoxy-3,3′,5-trihydroxybibenzyl (26). Compound 20 (1 g, 2 µmol) was dissolved in dry tetrahydrofuran (15 mL) under a N2 atmosphere; NaH (0.0814 g, 2 µmol) and 11 (0.591 g, 1.86 µmol) were added to the mixture, which was stirred during 3 h. After this period of time, water was added and the product extracted with EtOAc.…”

Selektive katalytische Hydrierungen und Hydrogenolysen, 4. Mitt. Darstellung von 1‐Benzylisochinolinen

“…Man isolierte nicht das entsprechende 2-Cyanobenzylisochinolin 4n sondern ein tiefgelbes, kristallines Produkt, das in Losungsmitteln wie Ether oder Chloroform bemerkenswert fluoreszierte. Nach eiementaranalytischen sowie IR-, 'H-NMR-, I3C-NMR-und MS-spektroskopischen Daten handelt es sich dabei um das bisher nicht bekannte 8H-8-Iminodibenzo[a,g]chinolizin (6).…”