JT VAE method decomposes every molecule into building blocks. One of the central assumptions that we used in our work is that the dictionary of simple structures forming the molecules is large enough for decomposing any possible molecule. This assumption is rarely satisfied when we change from one chemical database to another. Therefore, for the MIX dataset we expanded the vocabulary of simple compounds as much as possible. In particular, we grow the dictionary from 780 original building blocks covering the ZINC database in JT VAE to 2327 basic objects spanning MIX. The total number of molecules in MIX is 355796.