Novel rearrangements of 3-ylidene-piperazine-2,5-dione (1) were achieved affording Cope rearrangement products 3 and 4 under neutral conditions or tricyclic piperazine-2,5-diones 5, rac-6 and 7 by additional tandem cyclisation in formic acid. Cope rearrangement products 3 and 4 were transformed into new quaternary α-amino acids 9 and 11 by hydrogenation and hydrolysis.