In addition to the toxic indolizidine alkaloid swainsonine, the diablo locoweed (Astragalu oxyphysus) has been found to produce [1,8a-trans]-1-hydroxyindolizidine and [1,8a-trans-1,2-cis]-1,2-dihydroxyindolizidine, known precursors of swainsonine in the fungus Rhizoctonia leguminicola. As in the fungus, [G-3H]-pipecolic acid is incorporated into all three alkaloids. It is proposed that swainsonine biosynthesis in A. oxyphysus occurs by a pathway very similar to the fungal route. © 1988.