Generative machine learning models sample drug-like molecules from chemical space without the need for explicit design rules. A deep learning framework for customized compound library generation is presented, aiming to enrich and expand the pharmacologically relevant chemical space with new molecular entities 'on demand'. This de novo design approach was used to generate molecules that combine features from bioactive synthetic compounds and natural products, which are a primary source of inspiration for drug discovery. The results show that the data-driven machine intelligence acquires implicit chemical knowledge and generates novel molecules with bespoke properties and structural diversity. The method is available as an open-access tool for medicinal and bioorganic chemistry.Innovative molecular design methods are needed to support medicinal chemistry by efficient sampling of untapped drug-like chemical space 1,2,3 . Recently, the field of drug design has adopted so-called generative deep learning models to construct new molecules with desired properties 4,5,6,7,8 . Deep learning methods represent a class of machine learning algorithms that learn directly from the input data and do not necessarily depend on rules coded by humans 9,10 . Some of these methods implement a language modeling approach 11 , where an artificial neural network aims to learn the probability of a 'token' (e.g., a word or a character) to appear in a sequence based on the distributions all previous tokens in a sequence 12 . Through this process, deep neural networks can learn the features of sequential data. Once trained, these models can generate novel sequences based on the sampled feature distributions.