A mixture 9.7 g of (S)-3-[[(1,1-dimethylethyl)-dimethylsilyl]oxy]-1-(2-propynyl)-2-pyrrolidinone, 50 ml of dioxane, 5.7 g of piperidine, 1.8 g of paraformaldehyde, 10.5 ml of acetic acid and 0.16 g of cupric chloride was stirred for 30 minutes and then refluxed for 2 hours. The mixture was cooled in an ice bath, basified with ammonium hydroxide and diluted with water and dichloromethane. The dichloromethane solution was washed with water, dried and concentrated in vacuo, giving the desired product as an oil, [α]D26 =-32° (dichloromethane).
