Abstract: | Although the epimerization of lupinine ( 1 ) has been largely investigated, a previously not observed compound of formula C10H17NO was now isolated from the mixture of alkaloids that remains after the separation of epilupinine ( 2 ). It is insoluble in dry Et2O but soluble in EtOH, from which it is recovered as an Et2O‐soluble oil that slowly returns to the Et2O‐insoluble solid form. For these characteristics and based on GC/MS, 1H‐NMR, and IR data, it is considered as the inner salt 6 of the common enolic form 5 of lupinal ( 3 ) and epilupinal ( 4 ), with which it is in equilibrium when standing in solution (see Scheme 1). The oily form, but not the solid one, is able to improve the conversion of 1 to 2 , establishing the role of the aldehydes in the epimerization process. It was observed that also 2 can be converted to 1 . Finally, the solid lupinal described by Zaboev should be considered as being identical to the now isolated inner salt 6 , while the oily epilupinal of Wicky and Schumann is, indeed, a mixture of epilupinal ( 4 ) with a minor amount of lupinal ( 3 ), which, on standing, is converted to the inner salt 6 of the common enolic form 5 . |