Lignans, neolignans, and related compounds

Abstract

Lignans2.1 Dibenzylbutanes, Dibenzylbutyrolactones, and Substituted Furans This Section covers those lignans containing only one carboncarbon bond (8-8') between the two shikimate-derived biogenetic subunits.' meso-Nordihydroguaiaretic acid (1) was used for many years

Biomimetic Synthesis of Lignans

“…Upon treatment of 33 with Tl 2 O 3 in trifluoroacetic acid (TFA) a C1 epimeric, des-4-hydroxypodophyllotoxin (34) results (Scheme 18.4). Under hypervalent iodine or ruthenium catalysis, an unexpected eight-membered ring (35) forms exclusively [30]. Thus, with the proper metal catalysis, a biomimetic approach to podophyllotoxin is possible, but other routes have proven more direct and, importantly, enantioselective [28].…”

“…Further diversity emanates from the degree of core oxidation and the stereochemistry of pendant aryl groups (exo or endo face). Representative furofurans 36-41 ( Figure 18.3) are highlighted, and several excellent reviews have been written [32][33][34][35][36][37]. This class of lignans has demonstrated a wide range of biological activities with therapeutic relevance, and is found in traditional medicines [32,38].…”

“…This class of lignans has demonstrated a wide range of biological activities with therapeutic relevance, and is found in traditional medicines [32,38]. Like podophyllotoxin (15) and related compounds, numerous synthetic routes have been developed to access furofurans based on acyl anion additions, aldol chemistry, cycloaddition/rearrangements, and radical/photochemistry [30][31][32][33][34][35][36]. Here, we discuss the biomimetic, oxidative (β -β ) dimerization of cinnamyl derivatives, which follows the synthetic route illustrated in Scheme 18.3 for the biomimetic synthesis of (+)-pinoresinol (17).…”

Potencial alelopático de duas neolignanas isoladas de folhas de Virola surinamensis (Myristicaceae)

“…Quando se observam os efeitos médios promovidos individualmente por cada substância testada sobr e a germin ação das sementes (Tabela 3) e o desenv olvimento da radícula (Tabela 4) e do hipocótilo (Tabela 5), verificase que, independentemente do fator da planta analisado, a surinamensina inibiu, com maior ordem de grandeza, todos os fatores analisados das plantas, indicando que essa substância possui maior potencial como aleloquímico do Nos últimos anos, vários trabalhos em que se analisaram a química e a atividade biológica das lignanas e neolignas foram public ados (Gottieb, 1978;Whitting, 1987;Mac Rae & Tower s, 1984). Estudos como os de Swain (1977) e Russell & Fenemore (1973) têm classificado esses compostos como agentes de defesa contra o ataq ue de insetos.…”

Structural Diversity in Lignans and Neolignans

“…Lignans have been the subject of several reviews, notably in two books entirely devoted to them (5,7), in chapters of monographs (8,9), and several journal reviews (6,(10)(11)(12)(13)(14)(15)(16)(17)(18). They have become topical in recent times because increasing numbers of them have been described, from 14 in Haworth's 1936 review (7) to 440 in 1987 (5) (exclusive of neolignans), and because of their strong and varied biological activities.…”