Lignans chemical synthesis

The structure (121) of thomasic acid was established by extensive spectroscopic and chemical degradation studies (116,119,120) and presents several interesting features. It is one of the few lignans occurring naturally in racemic form and in possessing a free carboxyl group. In addition, the trans vicinal substituents (at C-1,2) adopt a diaxial conformation. The synthesis of this product (Scheme 25) was... 

The leaf-closing substance 79 has been isolated from a nyctinastic plant," and compound 80 is a new lignan glycoside isolated in tiny proportions from the roots of Saussurea lappa Xyloside 81 is a new glycoside isolated from the mycelia of Hericium erinaceum which contains compounds that stimulate nerve growth factor synthesis. Two derivatives were made by chemical transformations. 

There is at present little need for reviews on chemistry and synthesis of lignans and neolignans. An adequate chemical coverage up to mid-1976 (122) was subsequently complemented up to the end of 1983 (56, 164). Synthesis was covered in a very substantial paper published in 1982 (161). This does not mean, of course, that after the indicated dates science has lost interest in lignoids. Indeed, precisely the opposite has happened due to the powerful stimulus provided by the discovery of new and potentially exciting applications. Concomitantly, synthetic procedures became more varied (16) and analytical methods became more sophisticated. 

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