Medicinal plants of southern Africa. Part 2. Synthesis of 1,3-bis-(4-methoxyphenyl)penta-1,4-diene, a stereoisomer of dimethylhinokiresinol, and its 4-monomethoxy analogue

A six-step synthesis of the title compounds (6) and (7) from prop-2-yn-1-ol, and proceeding via 3-(4-methoxyphenyl)prop-1-yne, is described. Detailed 1H n.m.r. spectral analysis (500 MHz) suggests that the synthetic compounds have a 1,2-E stereochemistry in contrast to the Z-configuration present in the naturally occurring hinokiresinol (3). By utilizing a different, and much less efficient route, a small quantity of (Z)-3-(4-methoxyphenyl)-1-phenylpenta-1,4-diene (5) was obtained.