Condensation of the isoprenoid and amino precursors in the biosynthesis of domoic acid

► Reacting domoic acid with chloroformates yields a derivative analyzable by GC-MS. ► GC-MS detects incorporation of isotopically-labeled precursors into domoic acid. ► C1 of geranyl diphosphate is not oxidized in domoic acid biosynthesis.