Structure of 1-(4-[2-(diethylamino)ethoxy]phenyl)-2-(4-methoxyphenyl)-1-phenylethan- 1-ol, the non-steroidal antiestrogen MER25.

C27H33NO3, M(r) = 419.6, monoclinic, P2(1)/a, a = 22.833 (6), b = 9.370 (3), c = 11.434 (4) A, beta = 110.71 (8) degrees, V = 2288.2 A3, Z = 4, Dx = 1.22 g cm-3, lambda (Cu K alpha) = 1.54178 A, mu = 5.8 cm-1, F(000) = 904, T = 138 K, R = 0.049 for 3265 observed reflections. The molecule of MER25 assumes an extended conformation with rings alpha' and beta in an antiperiplanar (trans) conformation giving the solid-state conformer a closer resemblance to the estrogenic (E) isomer of tamoxifen than the antiestrogenic (Z) isomer. The geometrical features of the triarylethan-1-ol moiety are comparable to related structures but the orientations of the phenyl rings are different. The O-C-C-N segment in the (diethylamino)ethoxy side chain has the uncommon trans conformation instead of the more commonly observed gauche conformation seen in tamoxifen and many of its derivative structures. The amino N atom forms a hydrogen bond with the hydroxyl group of a neighboring molecule to form an infinite chain along the b axis.