Corrigendum to <‘Synthesis and biological evaluation of 2,6-disubstituted-9H-purine, 2,4-disubstitued-thieno[3,2-d]pyrimidine and -7H-pyrrolo[2,3-d] pyrimidine analogues as novel CHK1 inhibitors’ [Eur. J. Med. Chem. 151 (2018) 836–848]