  Deep generative models have been shown powerful in generating novel molecules
with desired chemical properties via their representations such as strings,
trees or graphs. However, these models are limited in recommending synthetic
routes for the generated molecules in practice. We propose a generative model
to generate molecules via multi-step chemical reaction trees. Specifically, our
model first propose a chemical reaction tree with predicted reaction templates
and commercially available molecules (starting molecules), and then perform
forward synthetic steps to obtain product molecules. Experiments show that our
model can generate chemical reactions whose product molecules are with desired
chemical properties. Also, the complete synthetic routes for these product
molecules are provided.
