Simple synthesis of oxiranylidene-2,2-bis(phosphonic acid): Tetrabenzyl geminal bisphosphonate esters as useful intermediates

Tetrabenzyl geminal bisphosphonate esters are shown to be useful synthetic equivalents of 1,1-bis(phosphonic acid)s which may be easily functionalized at the central carbon atom without phosphonate ester hydrolysis. The parent bis(phosphonic acid) unit is readily regenerated by hydrogenolysis. The chemistry is used to prepare the elusive epoxide oxiranylidene-2,2-bis(phosphonic acid) by a short and reliable procedure.