1.1: methyllithium / formaldehyde diethyl acetal; tetrahydrofuran / -70 - -60 °C / Inert atmosphere 1.2: 0.5 h / -50 - -40 °C / Inert atmosphere 1.3: -60 - -50 °C / Inert atmosphere 2.1: hydrogen / palladium 10 on activated carbon / ethyl acetate; water / 60 °C / 3000.3 Torr 3.1: oxalyl dichloride; dimethyl sulfoxide / dichloromethane / 1 h / -70 - -60 °C 3.2: -70 - 0 °C 4.1: trifluoroacetic acid / acetonitrile / 16 h / 15 - 30 °C 5.1: Lipase PS SD / acetone / 22 h / 50 - 60 °C / pH 8 / Enzymatic reaction View Scheme