Three contiguous stereocenters with syn-anti structure on the 3-(1-hydroxyalkyl)pyrrolidinone were constructed in one step with high yields and high diastereoselectivity by an Et2AlCl-catalyzed group transfer radical cyclization reaction from N-alkenyl-beta-hydroxyalkanamides with 125-W UV lamp irradiation. The relative stereochemistry was confirmed by X-ray analysis.