Fig. 10: RetroTide algorithm for the design of PKSs from a target chemical structure.

The RetroTide algorithm has the following steps: a The user provides a desired target chemical structure. b RetroTide loads all possible PKS starter module final structures. c The cartesian product between all possible starters, and all possible extension modules is used to compute all possible 1 module PKS products. These extension module structures are pre-computed once and reused as RetroTide runs. d All structures are compared with the user defined similarity metric to the defined target, and only the N (a user selectable parameter) top scoring designs are retained. Next, steps (c) and (d) are repeated iteratively adding all possible single PKS modules to the end of each of the best scoring designs from the previous round, until scores stop increasing for each round and then the algorithm halts, providing the best scoring designs to the user. Finally, the best scoring designs are optionally “released” as lactone/lactam, or carboxylic acid products.