Metaldehyde comes to mind, which is commonly sold as a snail poison in gardening. Where Paraldehyde is acetaldehyde trimer, Metaldehyde is the tetramer, an octagonal ring. I wouldnt go ingesting it though. Vomiting, convulsions, rapid death. If you make simple sedative molecules too big, they become convulsants. Going from Paraldehyde to Metaldehyde, that barrier is crossed. A pity, its a crystalline solid.