Molecular design and synthesis of B-10 carriers for neutron capture therapy

The authors have developed several new synthetic methods for B-10 containing bio-related molecules. The palladium-catalyzed coupling reaction of halogenated nucleoside derivatives with the aryltin compound having a boronic moiety proceeded chemoselectively at the C-Sn bond rather than the C-B bond to give boron containing nucleoside derivatives in good yields. The use of Pd(PPh3)4 as a catalyst, and the use of a less polar solvent such as toluene and a higher reaction temperature were essential to achieve the coupling. The use of acetonide and methoxymethyl as the sugar protecting groups, or conducting the reaction without protection gave poor results. The sterically bulky t-butyldimethylsilyl group afforded the coupling products in much higher yields