administering a composition comprising a therapeutically effective amount of a pharmaceutically acceptable carrier and a compound having the formula of:

and pharmaceutically acceptable salts thereof, wherein X is a member selected from the group consisting of —O— and —NH—;

Y is a member selected from the group consisting of —O— and —S—;

R¹, R² and R³ are each members independently selected from the group consisting of (C₂-C₂₄)acyl;

R⁴ is a member selected from the group consisting of —H and —PO₃R⁷R⁸, wherein R⁷ and R⁸ are each members independently selected from the group consisting of —H and (C₁-C₄)alkyl;

R⁵ is a member selected from the group consisting of —H, —CH₃ and —PO₃R⁹R¹⁰, wherein R⁹ and R¹⁰ are each members independently selected from the group consisting of —H and (C₁-C₄)alkyl;

R⁶ is selected from H, OH, (C₁-C₄)alkoxy, —PO₃R¹¹R¹², —OPO₃R¹¹R¹², —SO₃R¹¹, —OSO₃R¹¹, —NR¹¹R¹², —SR¹¹, —CN, —NO₂, —CHO, —CO₂R¹¹, and —CONR¹¹R¹², wherein R¹¹ and R¹² are each independently selected from H and (C₁-C₄)alkyl, with the proviso that when R⁴ is —PO₃R⁷R⁸, R⁵ is other than —PO₃R⁹R¹⁰;

wherein “*¹”, “*²”, “*³” and “**” represent chiral centers;

wherein the subscripts n, m, p and q are each independently an integer from 0 to 6, with the proviso that the sum of p and m is from 0 to 6.