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Chromatographic R Mw and log k' w parameters have been used as alternatives to the shake flask n-octanol/water partition coefficient method to study the lipophilic character of several known pyrimidinic nucleoside derivatives and two novel ones. The R M and log k' values were measured by means of reversed-phase thinlayer chromatography (RP-TLC) and reversed-phase high performance liquid chromatography (RP-HPLC) respectively. Good linear relationships were observed between log P values obtained from the classical shake flask method (log P o/w ) and each one of those obtained by chromatographic techniques (log P RP-TLC and log P RP-HPLC ) and by theoretical calculations using the CLOGP program (log P CLOGP ). The R Mw and log k' w values have proven to be reliable parameters for describing the lipophilic properties of this family of compounds. 855

An efficient, short synthesis of four potential prodrugs of 3'-azido-3'-deoxythymidine (AZT) and their antibacterial activity are reported. The 5'-OH group of AZT was functionalized with oxalyl chloride obtaining an acyl chloride derivative (AZT-Ox), which by further transformation with leucine, isoleucine and valine amino acids led to the corresponding AZT analogs, namely AZT-Leu, AZT-iLeu and AZT-Val. A carboxyl acid derivative (AZT-Ac) was also obtained by hydrolysis of AZT-Ox. These compounds, which exhibit anti HIV activity, have killed collection and clinical strains of some opportunistic infectious agents in AIDS-related complex. Thus, the clinical strains, K. oxytoca, S. typhi and K. pneumoniae, and collection strain K. pneumoniae ATCC 10031 showed sensitivity to antibiotics. The activity order for the studied compounds against the most sensitive strain (K. pneumoniae ATCC 10031) was AZT-Leu > AZT-iLeu > AZT-Val > AZT-Ac > AZT. On the other hand, the activity order for the second most sensitive strain (K. oxytoca) was AZT-Leu > AZT-Val = AZT-Ac > AZT-iLeu > AZT. The most effective antibacterial drug AZT-Leu, M.I.C.=0.125 microgmL(-1)) was 16 times more active than AZT (AZT, M.I.C.=2 microg mL(-1)) against K.