Efficient synthesis of methylenebis(phosphonate) analogues of P-1,P-2-disubstituted pyrophosphates of biological interest. A novel plausible mechanism

Synthesis of novel nucleoside bicyclic trisanhydrides 7 in the reaction of nucleoside-5'-methylenebis-(phosphonate)s (4) with DCC is described. They were obtained by P-1,P-3- and P-2,P-3-dehydration of initially formed P-1,P-2,P-3,P-4-bismethylenetetraphosphonate 6. Reaction of 7 (N = 2',3'-O-isopropylideneadenosin-5'-yl) with 2',3'-O-isopropylidenetiazofurin gave, after hydrolysis and deisopropylidenation, beta-methylene-TAD (10a), the known potent inhibitor of inosine monophosphate dehydrogenase (IMPDH). Similar reaction of 7 with benzyl 2,3-O-isopropylidene-beta-D-riboside followed by hydrolysis and deprotection afforded a new methylenebis(phosphonate) analogue of ADP-ribose 10b. Upon reaction of 7 with riboflavin, the corresponding beta-methylene-FAD (10c) was obtained. Bicyclic trisanhydride 7 prepared from (2',3'-O-isopropylidene-N-4-acetylcytidin-5'yl)methylenebis(phosphonate) was used in the synthesis of the methylenebis(phosphonate) analogues of CDP-ethanolamine 10d and CDP-dipalmitoylglycerol 10e.