GuacaMol's Distribution-Learning Benchmarks . The total number of compounds obtained from ChEMBL was 1,352,672, which were divided into 1,273,104 for training and 79,568 for validation. As the second dataset, compounds were obtained from ZINC , where drug-like compounds are registered, in order to evaluate the capability to optimize the physicochemical properties of molecular generation. The number of compounds obtained from ZINC was 249,456, which were divided into 199,565 for training and 49,891 for validation.