Phosphonate derivatives are frequently used as re- placements of the phosphate moiety of biologically active mo1ecules.l Substitution of a methylene or difluorometh- ylene group for one of the bridging oxygen atoms of a phosphate provides a nonhydrolyzable analogue of a phosphoester linkage.2 Phosphonate derivatives have recently been exploited as inhibitors of proteases and esterase^,^ mechanistic probes of PLAz,4 and haptens for the production of catalytic ...
