This invention relates to compounds of the general formula: ##STR00001##
in which R.sup.A, R.sup.B, R.sup.C and R.sup.D are as defined herein, and
to their preparation and use. In these compounds, R.sup.B is an
aliphatic, heteroaliphatic, aryl, or heteroaryl moiety which comprises
one or more phosphorus-containing moieties.