[CH3:1][C@@H:2]([CH2:11][C:12]#[CH:13])[CH2:3][O:4][CH:5]1[CH2:10][CH2:9][CH2:8][CH2:7][O:6]1.C([Li])CCC.CN(C)[C:21](=[O:23])[CH3:22].O.C(O)(=O)CC(CC(O)=O)(C(O)=O)O>C1COCC1.O.CCCCCC>[CH3:1][C@H:2]([CH2:3][O:4][CH:5]1[CH2:10][CH2:9][CH2:8][CH2:7][O:6]1)[CH2:11][C:12]#[C:13][C:21](=[O:23])[CH3:22]To a solution of 100.0 g (RS)-2-{[(S)-2-Methylpent-4-in-1-yl]oxy}3,4,5,6-tetrahydro-2H-pyran (Ireland, Robert E. et al., Tetrahedron, 1997, 53, 39, 13221-13256) in 200 ml THF were added, dropwise at −30° C., 439 ml n-butyllithium (15% in hexane). The solution was stirred for 20 minutes at −30° C. and 20 minutes at −20° C. After cooling to −30° C., a solution of 95.6 g N,N-dimethylacetamide in 200 ml THF was added during 15 minutes and the reaction mixture was stirred for 30 minutes at −20°. The reaction mixture was then poured into a stirred precooled (0° C.) mixture of 1000 ml hexane and a solution of 104,8 g citric acid monohydrate in 700 ml water. The aqueous phase was separated and the organic phase was washed with 300 ml water and then filtered over 100 g silica gel. The silica gel was washed with 1000 ml hexane. The combined eluates were reduced to an oil by vacuum distillation.
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