Patent ID: 7262182

Claim:
A compound of formula B: where: each R is independently hydrogen, C 1-6 alkyl, or —CH 2 CH 2 X, where each X is independently Cl, Br, C 1-6 alkanesulfonyloxy, halo-C 1-6 alkanesulfonyloxy, or benzenesulfonyloxy optionally substituted with up to three substituents selected from halo, C 1-3 alkyl, halo-C 1-3 alkyl, C 1-3 alkyloxy, or halo-C 1-3 alkyloxy, provided that at least two R's in each phosphorodiamidate group are —CH 2 CH 2 X; and R 2 is optionally substituted alkanediyl, optionally substituted heteroalkanediyl, optionally substituted arenediyl, optionally substituted arenedialkyl, optionally substituted heteroarenediyl, or optionally substituted heteroarenedialkyl, or its salt.