Complex sentence: Ergot contains no lysergic acid diethylamide (LSD) but instead contains ergotamine, which is used to synthesize lysergic acid, an analog of and precursor for synthesis of LSD.
Split into simpler sentences: Ergot contains no lysergic acid diethylamide (LSD) but instead contains lysergic acid as well as it's precursor, ergotamine. Lysergic acid is an analog of and precursor for synthesis of LSD.