8 -Hydroxy-lignan

Both, a-hydroxylated lignans of the dibenzyllactone-type and of the biarylcyclooctane-type have been enantioselectively prepared from the corresponding / -benzyl-y-butyrolactones via a-alkylation followed by a-oxy-genation (Scheme 5). The hydroxy group was introduced in two different... 

Dimethoxy-4, 4"-hydroxy-2,3-di-benzyl-butyrolactone 4 -0-Glc (lignan glucoside)... 

Natural products 130-140 are dibenzocyclooctadiene lignans (Figure 9-8). Structurally, they contain a linked biphenyl or phenyl/ketocyclohexadiene system, which can have either an S- (130-136) or R-configuration (137-140). Each ring is substimted at positions 1, 2, 3 and 12, 13, 14 with combinations of methoxy, methylenedioxy, or hydroxy groups. Four carbons C-6 C-9 and the biphenyl link-... 

The monographs (8,9) also present clear expositions of methods of synthesis. A recent communication addressing a short approach to both symmetrical and unsymmetrical tetrahydrofurofuran lignans is outlined in Scheme 32 (149). Michael addition of the sodium salt of the silyl monoprotected diol (155) to the a-sulfonylcinnamate (156) gave the ether (157) which on desulfurization and hydrolysis gave the hydroxy acid (158). Lactonization of (158) by the Mukaiyama method... 

Oxidative cleavage of the furo-furan unit of lignans delivers hydroxy ketones. However, the successful transformation must be carried out at -20° and under high dilution. 

A large number of chiral a,a -orz/zo-disubstituted diphenyldiselenides with hydroxy and amino functions (e.g., 244 and 245) have been prepared by Wirth and co-workers. They were used as electrophiles for a number of asymmetric addition and cyclization reactions including the total synthesis of the lignan derivatives (-l-)-samin and (-l-)-membrine as well as catalysts in the asymmetric diethylzinc addition to aldehydes. 

K Kuriyama, T Murai. Scavenging of hydroxy radicals by lignan glucosides iu germinated sesame seeds. Nippon Nogei Kagaku Kaishi 69 703-705, 1995. 

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