Abstract The stereochemistry of substitution at dihalomethylphosphonothioates is the same as for phosphogothioates whereas that for monohalomethylphosphono- thioates is similar to the unsubstituted phosphoflothioates. ... It has been suggested' that halomethylphosphonates are electronically better analogues of natural phosphates than the corresponding unsubstituted phosphonates and may therefore be useful in studies of biosynthetic pathways and enzyme ...