Synthesis, conformation, and chirality of di-O-methylsequirin D, a biogenetically novel metabolite of Sequoia sempervirens
Abstract
The synthesis of (±)-di-O-methylsequirin D (14; R = H) is reported. A Grignard reaction between 3,3-ethylenedioxypropylmagnesium bromide and deoxyanisoin gave the key alcohol (5), which was transformed into (14) by way of the acid (11) and the tetralone (12). Measurement of the 3-H2,4-H coupling constants in (14; R = D) show the compound to have a 4-axial anisyl substituent, while c.d. data indicate a left-hand skewed styrene geometry in the dimethyl ether of the natural norlignan (2). The absolute configuration of (2) is hence deduced as 1R. The biosynthesis of sequirin-D and the origin of the m-hydroxycinnamate unit are discussed.