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Step 1: Synthesis of 8-methyl-1,4-dioxaspiro[4.5]decan-8-ol: 1,4-dioxaspiro[4.5]decan-8-one (7.8 g, 50.0 mmol) was dissolved in dry THF (75 mL) and cooled to -78 °C under argon protection. Methyl lithium solution (1.5 M in ether, 43.3 mL, 65.0 mmol) was added slowly, controlling the reaction temperature to not exceed -55 °C. After addition, the reaction mixture was continued to be stirred at -55 °C for 4 hours. Subsequently, the reaction system was slowly warmed to room temperature and the reaction was quenched with saturated NH4Cl solution. The organic layer was separated and concentrated in vacuum, and the resulting residue was purified by silica gel column chromatography (eluent ratio: ethyl acetate:petroleum ether = 1:9 to 1:3) to afford the target product, 8-methyl-1,4-dioxaspiro[4.5]decan-8-ol, as a white solid (6.8 g, yield: 80%).