Dihydroergotamine Mesylate Impurity D (2_-epi- 9, 10 -dihydroergotamine)

Dihydroergotamine Mesylate Impurity D (2-epi-9,10-dihydroergotamine) is a stereoisomeric degradation product arising from the reduction of the 9,10-double bond in the tetracyclic ergot alkaloid core of ergotamine. The 2-epi configuration introduces a reversed stereochemistry at the C2 position, while the dihydro moiety saturates the pyrrolizine ring. This impurity retains the indole, methoxy, and amino acid-derived side chain functionalities critical to the parent compound's pharmacophore. It serves as a reference standard for HPLC-based quantification of process-related impurities in ergotamine-derived APIs.