Lignan Skeleton Research Articles

Alpha,beta-Dibenzyl-gamma-butyrolactone lignan alcohols: total synthesis of (+/-)-7'-hydroxyenterolactone, (+/-)-7'-hydroxymatairesinol and (+/-)-8-hydroxyenterolactone.

Two trans-alpha,beta-dibenzyl-gamma-butyrolactone lignans carrying a hydroxyl group at the beta-benzylic carbon atom and a alpha-hydroxy alpha,beta-dibenzyl-gamma-butyrolactone lignan were synthesized in racemic form using the tandem conjugate addition reaction to construct the basic lignan skeleton. Subsequent reaction steps involved either a catalytic reduction of the regenerated keto group to the alcohol, or a hydrogenolysis to benzylic methylene followed by lactone enolate formation and oxidation to give the alpha-hydroxybutyrolactones. These procedures were applied for the synthesis of 7'-hydroxyenterolactones and 7'-hydroxymatairesinols, and 8-hydroxyenterolactones, respectively. The diastereomeric mixtures of these compounds were separated either by HPLC techniques or column chromatography and the structures were elucidated using NMR spectroscopy.

Transformations of lignans, part IV. Acid-catalysed rearrangements of gmelinol with BF 3-etherate and study of a product with a unique lignan skeleton formed by further oxidation with DDQ

Reaction of gmelinol 1 with BF 3-etherate followed by treatment with various additives gave two isomeric products 2 and 5 formed by rearrangement of the 2,6-diaryl-3,7-dioxabicyclo[3.3.0]octane skeleton. Compounds 2 and 5 on oxidation with DDQ in trifluoroacetic acid or benzene produced enantiomers 8 and ent-8 respectively, which have a “distorted furofuran” skeleton. Compound 5 on reduction with triethylsilane and BF 3-etherate gave 13, which is isomeric with di- O-methyl cycloolivil.

A tetrameric derivative of caffeic acid from Rabdosia japonica

A component which showed tanning activities, was isolated from Rabdosia japonica, and was named rabdosiin. It was shown to be a tetramer of caffeic acid with a lignan skeleton.

Synthesis of the aryltetralin lignan skeleton via the Prins reaction

Synthesis of the aryltetralin lignan skeleton via the Prins reaction

Synthesis of lignan lactones by conjugate addition of thioacetal carbanions to butenolide

The conjugate addition of carbanions dervied from arylbis(phenylthio)methanes to butenolide followed by trapping of the enolate anion so generated by a benzyl halide affords adducts (8) containing the basic lignan skeleton. Desulphurisation of these adducts by Raney nickel affords a short efficient synthesis of trans-dibenzylbutyrolactones and this route has been used to prepare enterolactone (9c) and an antitumour lignan (9b), derived from Bursera schlechtendalii. Treatment of the adducts (8) with heavy-metal salts induces cyclisation leading to arylnaphthalene lactones, including retrojusticidin B (13).

Synthesis of a lignan skeleton via nickel- and palladium-phosphine complex catalyzed grignard coupling reaction of halothiophenes

A lignan skeleton is prepared in good yield through desulfurization of 3,4-dibenzyl-thiophene or 2,5-diaryl-3,4-dimethylthiophenes which are obtained by the nickel- or palladium-phosphine complex catalyzed Grignard cross-coupling reaction of halothiophenes.

A Simple Method for the Synthesis of Lignan Skeleton. Syntheses of (±)-Parabenzlactone and (±)-Hinokinin

Abstract The reaction of 2-aryl-2-lithio-l,3-dithianes with 2-butenolide followed by quenching with benzyl halides gave lignan skeleton in fairly good yield.