To a stirred solution of trimethylsilylacetylene (0.18 ml, 1.27 mMol) in THF (18 ml) at −78° C. is added n-Butyllithium (0.49 ml, 2.5 M in cyclohexane). After 5 minutes, [(R)-1-Formyl-3-(4-heptyloxy-phenyl)-1-methyl-propyl]-carbamic acid tert-butyl ester (200 mg, 0.51 mMol) in THF (2 ml) is added and the reaction is stirred at −78° C. for 5 hours. After that time, the cooling is removed and the reaction is stirred for 16 hours at RT. The reaction mixture is then poured onto a biphasic mixture of AcOEt and NaHCO3 (saturated aqueous solution). The aqueous phase is extracted with AcOEt (3 times). The combined organic layers are dried (Na2SO4) and concentrated under reduced pressure. Column chromatography eluting with 8%-45% AcOEt in heptane gives (R)-5-Ethynyl-4-[2-(4-heptyloxy-phenyl)-ethyl]-4-methyl-oxazolidin-2-one and its C5 epimer.
