A review with 114 references about mammalian lignans (enterolignans). Several aspects have been reviewed: the precursors of mammalian lignans and their biosynthesis, biological activities and health effects, metabolism (in vivo and in vitro) in human and animals, some synthetic strategies to obtain enterolignan skeleton types, including the synthesis of haptens and deuterated lignans, and finally an overview of the analytical methods to detect and quantify lignans in biological matrices and foods.

The asymmetric synthesis of a series of (7'S,8R,8'R)-7'-hydroxylignano-9,9'-lactones is presented, among them the mammalian lignan (7'S)-hydroxyenterolactone and (7'S)-parabenzlactone, allowing the stereochemistry of natural occurring (-)-parabenzlactone to be re-assigned. A hydroxylactone rearrangement and its possible mechanisms are discussed. Finally a brief survey of the current naming and numbering variants of 7'-hydroxylignano-9,9'-lactones is presented, along with a suggestion for harmonization of the nomenclature.

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Abstract:a-Hydroxynaphthylthiophthalimide (1) is a suitable precursor of the reactive ortho-thioquinone 2, which can be generated in situ and trapped by glycals. The reaction is an inverse electron-demand [42] cycloaddition that occurs in a totally regioselective and highly stereoselective way. A series of differently substituted glycals (3, 5 ± 12, 21, 22, 38) as well as various ortho-thioquinones (25 ± 27) are successfully used as electron-rich dienophiles and electron-poor dienes, respectively, with chloroform, dimethylformamide, and dimethyl sulfoxide as solvents. The stereochemistry of substituents on the dienophile strongly influences the selectivity of the cycloaddition, which becomes totally stereoselective when galactals 8 ± 10 or arabinals 21 and 22 are employed as dienophiles. Among the heterodienes tested, the a-naphthol derivative 25 and the tyrosine derivative 26 were successfully used to prepare the naphthyl-a-O-rhamnoside 32 a and the tyrosine-a-O-glucoside 34, respectively. Cycloadducts 4 a, 17, 24, and 33 a were successfully desulfurized, affording the corresponding aryl 2-deoxy-a-O-glycosides 39 and 40 ± 42.

Seven new dibenzylbutyrolactone and six new dibenzylbutanediol lignans were prepared to assist in the identification of a number of potential mammalian metabolites of the endocrine disrupting plant lignans syringaresinol and medioresinol, present in food.