compounds formally derived from an oxoacid RkE(=O)l(OH)m, (l ≠ 0) and an alcohol, phenol, heteroarenol, or enol by linking with formal loss of water from an acidic hydroxy group of the former and a hydroxy group of the latter, oksohapete ja alkoholide, fenoolide, heteroarenoolide või enoolide reageerimisel moodustunud ühendid