Synthesis of boron cluster lipids: closo-dodecaborate as an alternative hydrophilic function of boronated liposomes for neutron capture therapy.

We succeeded in the synthesis of the double-tailed boron cluster lipids 4a-c and 5a-c, which have a B12H11S moiety as a hydrophilic function, by S-alkylation of B12H11SH (BSH) with bromoacetyl and chloroacetocarbamate derivatives of diacylglycerols for a liposomal boron delivery system on neutron capture therapy. Calcein encapsulation experiments revealed that the liposomes, prepared from the boron cluster lipid 4b, DMPC, PEG-DSPE, and cholesterol, are stable at 37 degrees C in FBS solution for 24 h. [reaction: see text].