During many years we investigate the crystallochemical phenomena of polytypism, polysomatism and others in the crystals of the biologically active binary and mixed complexes with α- amino acids by the electron diffraction method. These phenomena, especially polytypism, serve as the base for prediction, modeling, and description of new unknown compounds. To gain these objectives the crystal structure of copper (II) mixed compound with glycine (Gly) and homoserine (Hoser): Cu2Gly2(D–Hoser)(L–Hoser) has been determined. The structure is made up from separated mirror equal complexes CuGly(D–Hoser) and CuGly(L–Hoser). The complexes of both types are united in the layers parallel to bc crystallographic plane. The complexes inside the layer are symmetry related by glide plane b. The adjacent layers are crystallographically related by translation [1/2 1/2 0]. It was established that the peculiarities of interlayer space and the nature of interlayer interactions in the crystals of Cu2Gly2(D–Hoser)(L–Hoser) make possible the other variants of mutual arrangement of the adjacent layers in the space. In this new predicted structure the adjacent layers are crystallographically related by translation [1/2 0 1/2]. Thus, both structures are built from the same initial structural unit (layer) and differ one from another only by the way of alternation of the structural unit in the crystal space. Thereby, both structures are polytypical modifications of the crystals Cu2Gly2(D–Hoser)(L–Hoser).