Synthesis and DNA Cleavage Activity of Bis-3-chloropiperidines as Alkylating Agents

Nitrogen mustards are an important class of bifunctional alkylating agents routinely used in chemotherapy. They react with DNA as electrophiles through the formation of highly reactive aziridinium ion intermediates. The antibiotic 593A, with potential antitumor activity, can be considered a naturally occurring piperidine mustard containing a unique 3-chloropiperidine ring. However, the total synthesis of this antibiotic proved to be rather challenging. With the aim of designing simplified analogues of this natural product, we developed an efficient bidirectional synthetic route to bis-3-chloropiperidines joined by flexible, conformationally restricted, or rigid diamine linkers. The key step involves an iodide-catalyzed double cyclization of unsaturated bis-N-chloroamines to simultaneously generate both piperidine rings. Herein we describe the synthesis and subsequent evaluation of a series of novel nitrogen-bridged bis-3-chloropiperidines, enabling the study of the impact of the linker structure on DNA alkylation properties. Our studies reveal that the synthesized compounds possess DNA alkylating abilities and induce strand cleavage, with a strong preference for guanine residues.