Jorunnamycins A-C (1a-c), three stabilized renicramycin-type bistetrahydroisoquinolines, were isolated from the mantles, the visceral organs, and the egg ribbons of the Thai nudibranch Jorunna funebris that was pretreated with potassium cyanide (KCN), along with five known compounds, renieramycins M (2m), N (2n), O (2o), and Q (2q) and mimosamycin (3). The structures of la-c were elucidated from spectroscopic data and by chemical conversion of renieramycin M (2m) into 1c via 1a. The chemical stability and the oxidative degradation generating simple isoquinoline alkaloids of a carbinolamine analog 1d, which was easily prepared by reacting 1c with silver nitrate in aqueous acetonitrile, are discussed. The results of cytotoxicity studies are also presented.