The present invention relates to new heterocyclic compounds of general formula (1) wherein the groups R
1
to R
7
, k, X and Y have the meanings given in the claims and specification, the isomers and salts thereof as well as the use thereof as medicaments. Background to the invention WO 01/36423 describes 3,4-dihydrospiro[chromene-2,4′-piperidine] derivatives for treating diseases of the central nervous system. Spirocyclic heterocycles as δ-opioid receptor ligands for treating pain and anxiety states as well as diseases of the gastrointestinal tract are known from WO 2005/033073. The aim of the present invention is to indicate new active substances which can be used for the prevention and/or treatment of diseases characterised by excessive or abnormal cell proliferation.