Each pair above are stereoisomers due to rearrangements between lysergic and isolysergic acids. The natural levorotataory ergot alkaloids are derived from lysergic acid, such as, ergotamine. the dextrorataory members such as ergotaminine are derived from isolysergic acid. The natural levorotatory alkaloids have powerful pharmacological action, whereas the corresponding dextrorotatory compounds posses only a fraction of the activity.