The invention relates to compounds of the formulae (I) and (II) in which R1, R2, R3, R4, R5, R8, X and m have the meaning indicated in the claims, and/or physiologically acceptable salts, tautomers and stereoisomers thereof, including mixtures thereof in all ratios. The compounds of the formula (I) can be used for the inhibition of serine/threonine protein kinases and for the sensitisation of cancer cells to anticancer agents and/or ionising radiation. The invention also relates to the use of the compounds of the formula (I) in the prophylaxis, therapy or progress control of cancer, tumours, metastases or angiogenesis disorders, in combination with radiotherapy and/or an anticancer agent. The invention furthermore relates to a process for the preparation of the compounds of the formula (I).