The thermostable transketolase from Geobacillus stearothermophilus (TK gst) was successfully engineered for the synthesis of aliphatic acyloins with varying carbon backbone lengths (C 5 À C 10) based on protein structure-guided studies. Efficient TK gst variants were identified with enhanced activities for substrate combinations of aliphatic aldehydes as acceptors together with aliphatic pyruvate homologues as donors. The TK gst single variant L382F was able to catalyze efficiently the transfer of the ketol group from hydroxypyruvate on all targeted aliphatic aldehydes (C 3 À C 8) to give the corresponding 1,3-dihydroxy ketones with good yields and excellent enantioselectivity. The combination of the H102L/H474S mutation previously designed for the improved utilization of aliphatic pyruvate homologues together with a F435I exchange gave the new variant H102L/H474S/F435I, which is able to transfer the acyl goup of 2-oxobutyrate and 2-oxovalerate to aliphatic aldehydes, giving mono hydroxylated ketones.

The ring-opening of epoxidized methyl oleate by aqueous H 2 O 2 has been studied using tungsten and molybdenum catalysts to form the corresponding fatty β-hydroxy hydroperoxides. It was found that tungstic acid and phosphotungstic acid gave the highest selectivities (92-93 %) towards the formation of the desired products, thus limiting the formation of the corresponding fatty 1,2-diols. The optimized conditions were applied to a range of fatty epoxides to give the corresponding fatty βhydroxy hydroperoxides with 30-80 % isolated yields (8 examples). These species were fully characterized by 1 H and 13 C NMR spectroscopy and HPLC-HRMS, and their stability was studied by differential scanning calorimetry. The thermal cleavage of the β-hydroxy hydroperoxide derived from methyl oleate was studied both in batch and flow conditions. It was found that the thermal cleavage in flow conditions gave the highest selectivity towards the formation of aldehydes with limited amounts of byproducts. The aldehydes were both formed with 68 % GC yield, and nonanal and methyl 9-oxononanoate were isolated with 57 and 55 % yield, respectively. Advantageously, the overall process does not require large excess of H 2 O 2 and only generates water as a byproduct.