Two main sources of compounds were employed in this work. The first is the Mcule catalogue , that contains more than 40 million compounds and their up-to-date prices compiled from more than a hundred vendors. In order to avoid common errors that may arise from the integration of different catalogues (misdrawn and incorrect structures), the catalogue is curated using the Mcule Advanced Curation process (MAC) that involves a rigorous molecule registration system including structural checks, and various steps of standardization, preparation and correction, ensuring that the information contained in the catalogue is highly reliable. From this catalogue we extracted the subset of in-stock compounds (~7M), that was divided into train, validation, and test partitions randomly. The price of each compound was collected on March 2021 from the Mcule database as the best price for 1 g of compound. Prices were then converted from $/g to $/mmol because, as found by Fukunishi et al. , correlations with SA measurements were stronger. All statistics and Figures included in this work are derived from the compounds in the test set except when explicitly stated. The test set is also referred to as the purchasable compounds dataset (PC) throughout this manuscript as it only contains purchasable compounds. For the generalizability study, a random subset of 100K virtual compounds was also extracted from the Mcule catalogue as a separate independent test set. The second source of compounds was the ZINC database from which we extracted a subset comprising only non-commercially available natural products, that we refer to as the NPNP (Non-Purchasable Natural products) dataset. We use this dataset as an approximate set of non-synthesizable compounds. We also employed two of the datasets compiled by Gao and Coley . These were their dataset of molecules compiled from five different sources: MOSES , ZINC , ChEMBL , Sheridan et al. , and GBD-17 ; and their dataset of de novo generated molecules comprising of two subsets of molecules optimized against multiple properties including or not the SAscore.