  The aim of this work is to bridge the gap between CC SNe and their remnants
by investigating how post-explosion anisotropies in the ejecta influence the
structure and chemical properties of the remnant at later times. We performed
three-dimensional magneto-hydrodynamical simulations starting soon after the SN
event and following the evolution of the system in the circumstellar medium
(consisting of the wind of the stellar progenitor), for 5000 years, obtaining
the physical scenario of a SNR. Here we focused the analysis on the case of a
progenitor red supergiant of 19.8 M_sun. We also investigated how a
post-explosion large-scale anisotropy in the SN affects the ejecta distribution
and the matter mixing of heavy elements in the remnant, during the first 5000
years of evolution. In the case of a spherically symmetric SN explosion without
large-scale anisotropies, the remnant roughly keeps memory of the original
onion-like layering of ejecta soon after the SN event. Nevertheless, as the
reverse shock hits the ejecta, the element distribution departs from a
homologous expansion, because of the slowing down of the outermost ejecta
layers due to interaction with the reverse shock. In the case of a large-scale
anisotropy developed after the SN, we found that the chemical stratification in
the ejecta can be strongly modified and the original onion-like layering is not
preserved. The anisotropy may cause spatial inversion of ejecta layers, for
instance leading to Fe/Si-rich ejecta outside the O shell, and may determine
the formation of Fe/Si-rich jet-like features that may protrude the remnant
outline. The level of matter mixing and the properties of the jet-like feature
are sensitive to the initial physical (density and velocity) and geometrical
(size and position) initial characteristics of the anisotropy.
