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The cis – trans isomerization of (thio)amides was studied by DFT calculations to get the model for the higher preference for the cis conformation by guided predictive chemistry, suggesting how to select the alkyl/aryl substituents on the C/N atoms that lead to the trans isomer. Multilinear analysis, together with cross-validation analysis, helped to select the best fitting parameters to achieve the energy barriers of the cis to trans interconversion, as well as the relative stability between both isomers. Double experimental check led to the synthesis of the best trans candidate with sterically demanding t -butyl substituents, confirming the utility of predictive chemistry, bridging organic and computational chemistry. 

Abstract Bacterial polyhydroxyalkanoates (PHAs) are a unique class of biodegradable polymers because of their biodegradability in ambient environments and structural diversity enabled by side‐chain groups. However, the biosynthesis of PHAs is slow and expensive, limiting their broader applications as commodity plastics. To overcome such limitation, the catalyzed chemical synthesis of bacterial PHAs has been developed, using the metal‐catalyzed stereoselective ring‐opening (co)polymerization of racemic cyclic diolides (rac‐8DL^R, R=alkyl group). In this combined experimental and computational study, polymerization kinetics, stereocontrol, copolymerization characteristics, and the properties of the resulting PHAs have been examined. Most notably, stereoselective copolymerizations ofrac‐8DL^Mewithrac‐8DL^R(R=Et, Bu) have yielded high‐molecular‐weight, crystalline isotactic PHA copolymers that are hard, ductile, and tough plastics, and exhibit polyolefin‐like thermal and mechanical properties.