Loline, a saturated pyrrolizidine-type alkaloid, was isolated from tall fescue (Festuca arundinacea) seed infected with the endophytic fungus Acrmonium cwnophialum. Procedures are described for the efficient conversion of loline to derivatives also known to occur naturally: norloline, N-formylnorloline, N-acetylnorloline, N-methylloline, N-formylloline, and Nacetylloline. The loline alkaloids are of interest as they are suspected contributors to several disease syndromes in cattle that consume endophyte-infected tall fescue. The structure of hydroxychlorololine, a reaction product of loline with HCI, was determined, and complete 'H- and "Cnmr assignments for all the lolines are reported.