Oxidative Coupling of Lignans. III. Non-Phenolic Oxidative Coupling of Deoxypodorhizon and Related Compounds

Abstract

Oxidative coupling of deoxypodorhizon (4) with thallium(III) oxide and trifluoroacetic acid may be controlled to give either deoxyisopodophyllotoxin (14) or isostegane (16). These results and those with related non- phenolic substances indicate that the aromatic substituents of the parent diarylbutane play an important role in determining the outcome of oxidative coupling.

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].…”

“…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).…”

Development and Application of New Oxidation Systems Utilizing Oxometalate Catalysts

“…102) A number of biogenetic-type arylaryl coupling reactions have been investigated using heavy metal oxidizing reagents such as mercury(II), thallium(III), vanadium(V), iron(III), manganese(IV), and ruthenium(IV) salts. [103][104][105][106][107][108] However, the yields are not always satisfactory. Moreover, heavy metal reagents are highly toxic and must be handled very carefully.…”

Constituents of Asarum sieboldii with Inhibitory Activity on Lipopolysaccharide (LPS)‐Induced NO Production in BV‐2 Microglial Cells

“…XII (12 g), eluted with hexane/CHCl 3 1 : 1, were further fractionated by FC (300 g SiO 2 ; hexane/AcOEt 99 : 1, 98 : 2, 95 : 5, 9 : 1. 4 : 1, then neat MeOH, 3 l each) to yield 4 (154 mg, 0.0051%) [26] and 5 (389 mg, 0.013%) [27]. Fr.…”

“…Herein, we describe the isolation, structural identification, and biological properties of ten known isolates from A. sieboldii, including the biologically active constituents (À)-sesamin (1) [14], (2E,4E,8Z,10E)-N-(2-methylpropyl)dodeca-2,4,8,10-tetraenamide (2) [14], kakuol (3) [10], and 3,4,5-trimethoxytoluene ( ¼ 1,2,3-trimethoxy-5-methylbenzene; 4) [26], as well as the inactive compounds methylkakuol (5) [27], 3,5-dimethoxytoluene ( ¼ 1,3-dimethoxy-5-methylbenzene) [28], safrole [29], asaricin [30], methyleugenol [12], and (À)-asarinin [14].…”