4-{[(1R)-6,7-Dimethoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-1-yl]methyl}-2-{[(1R)-1-(4-hydroxybenzyl)-6-methoxy-2-methyl-1,2,3,4-tetrahydroisoquinolin-7-yl]oxy}phenol