Conformation of 1-aryl-2-aryloxy-1-propanols: threo-1-(4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenoxy)-1-propanol

The title compound, C₁₇H₂₀O₅, (I), is structurally related to naturally occurring 1-aryl-2-aryloxy-1-propanols. Such compounds are of interest as lignin models, and neolignans of this type have been detected in a large number of plants. In the crystal structure of (I), the molecules adopt a conformation in which the aryl groups are far apart from each other. The O(aryloxy)—C—C—C(aryl) torsion angle is 177.76 (14)°. The conformation is compared with those of other compounds (neolignans and lignin model compounds) of the 1-aryl-2-aryloxy-1-propanol type (including some acetate derivatives). The comparison shows that in all the examined compounds the above-mentioned torsion angle is close to 180°, and the distance between the centers of the aromatic rings approaches the maximum achievable in most of the compounds. The hydrogen-bonding pattern of (I) is discussed in terms of graph-set theory.