methyl oxane-2-carboxylate

Conditions: temp:-78.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A solution of N,N-diisopropylamine (909 mg, 1.25 mL, 9 mmol) in tetrahydrofuran (4 mL) was stirred at −78° C. under nitrogen. n-Butyllithium (3.6 mL, 9 mmol, 2.5 M solution in hexane) was added dropwise and the reaction mixture was stirred at −78° C. for 30 minutes. A solution of tetrahydro-pyran-2-carboxylic acid methyl ester (864 mg, 6 mmol) in tetrahydrofuran (8 mL) was added and the reaction mixture was stirred at −78° C. for 20 minutes. Acetaldehyde (792 mg, 1.0 mL, 18 mmol) was added in one portion. The cooling bath was removed and the reaction mixture was stirred at room temperature for 1 h. The reaction mixture was cooled to 0° C. and ice-cold hydrochloric acid (2 M) was added to acidify the reaction mixture to pH 2. Sodium chloride was added to saturate the aqueous phase and the mixture was extracted with diethyl ether. The organic extracts were combined and washed with brine. The organic solution was filtered through a hydrophobic frit and the filtrate was evaporated. The residue was purified by silica gel chromatography using a gradient of pentane/diethyl ether 1:1 to 0:1 to afford the title compound (1.28 g) as an oil and as a 2:1 mixture of diastereoisomers. LCMS (m/z) 189.3 [M+H], Tr=1.23 min. the reaction mixture was stirred at −78° C. for 20 minutes The cooling bath was removed the reaction mixture was stirred at room temperature for 1 h The reaction mixture was cooled to 0° C. ice-cold hydrochloric acid (2 M) was added Sodium chloride was added to saturate the aqueous phase the mixture was extracted with diethyl ether washed with brine The organic solution was filtered through a hydrophobic frit the filtrate was evaporated The residue was purified by silica gel chromatography