IRA missed MRDs

When the decedent died, she had not taken MRDs from her IRA for several years. The IRA administrator will not take out catch up MRDs unless I provide some authority that shows they may be taken out, which they may. I'm just not sure of the legal authority.

The issue is that the IRA beneficiary is different from the estate beneficiary who would inherit the money from the MRD if it was part of an account held in the estate.

Does anyone know of any authority that says catch up MRDs can be taken out?