Structural studies of some hydroxyeriobrucinol derivatives

Single-crystal X-ray structure determinations of the acetate derivative of hydroxyeriobrucinol methyl ether (1) and eriobrucinol methyl ether (2) have been carried out and confirm their structures and relative configurations. A tentative assignment of absolute configuration for the system has been made on the basis of a structure determination carried out on a non-stoicheiometric brominated derivative (3) of (1), and is consistent with that derived for (-)-bruceol. Conformational inversion of the dihydropyran ring from a half-boat in (1) to a half-chair in the bromo-derivative is observed and parallels that noted in solution for these compounds.