1-Alkylcarbonyloxymethyl prodrugs of 5-fluorouracil (5-FU): synthesis, physicochemical properties, and topical delivery of 5-FU.

1-Alkylcarbonyloxymethyl (1-ACOM) prodrugs of 5-fluorouracil (5-FU) have been synthesized and characterized by their solubilities in isopropyl myristate (SIPM) and pH 4.0 buffer (SH2O), by their partition coefficients between isopropyl myristate (IPM) and pH 4.0 buffer (K) and by their abilities to deliver total 5-FU species into (Cs) and through (Ji) hairless mouse skin from an IPM vehicle. All of the prodrugs were much more lipophilic (SIPM) than 5-FU (> 60 times), and two members of the series (alkyl = C1 and C2, acetyl- and propionyloxymethyl) were also more soluble in water than 5-FU. The two more water-soluble members gave larger Ji values than the other members of the series, with C2 exhibiting the best biphasic solubility and the largest Ji value (16 times that of 5-FU). The ability of the 1-ACOM-5-FU prodrugs to deliver total 5-FU species into skin (Cs) was greater than the delivery of 5-FU by 5-FU, except for the last two members of series (alkyl = C7 and C9, octanoyl- and decanoyl-oxymethyl). However, the ratios of normalized Cs to Ji for the series was less than that exhibited by 5-FU, except for C7 and C9. Also, except for C9, significant amounts of intact prodrug as percentages of total 5-FU species were found in the receptor phases during the course of the diffusion cell experiments, ranging from 55% for C1 to 12% for C7.