Four series of nucleolipids with either uridine, 5-methyluridine, 5-fluorouridine, and 6-azauridine as β-D-ribonucleoside component have been prepared in a combinatorial (not parallel!) manner (see Formulae). All compounds have been characterized by elemental analyses, ESI mass spectrometry as well as by (1) H-, and (13) C-NMR, and UV spectroscopy. A selection of eight nucleolipids with different lipophilizing moieties, based on earlier findings, as well as of 5-fluorouridine as control were first tested on their cytotoxic effect towards PMA-differentiated human THP-1 macrophages. Those compounds which did not exhibit a significant inhibitory effect on the survival of the macrophages were next tested on their cytostatic/cytotoxic effect towards the human astrocytoma/oligodendroglioma GOS-3 cells as well as against the rat malignant neuroectodermal BT4Ca cell line. Additionally, induction of apoptosis of the cell lines was evaluated. It turned out that particularly a combined lipophilization of the nucleosides by an 2',3'-O-ethyl levulinate residue plus a farnesyl moiety at N(3) of the pyrimidine moiety of the corresponding nucleolipids leads to an active compound with the highest probability.

We report on the synthesis of two series of canonical purine ß‐d‐ribonucleoside nucleolipids derived from inosine and adenosine, which have been characterized by elemental analyses, electrospray ionization mass spectrometry (ESI MS) as well as by 1H and 13C NMR, and pH‐dependent UV/Vis spectroscopy. A selection of the novel nucleolipids with different lipophilic moieties were first tested on their cytotoxic effect toward human macrophages. Compounds without a significant inhibitory effect on the viability of the macrophages were tested on their cytostatic/cytotoxic effect toward human astrocytoma/oligodendroglioma GOS‐3 cells as well as against the rat malignant neuroectodermal BT4Ca cell line. In order to additionally investigate the potential molecular mechanisms involved in the cytotoxic effects of the derivatives on GOS‐3 or BT4Ca cells, we evaluated the induction of apoptosis and observed the particular activity of the nucleolipid ethyl 3‐{4‐hydroxymethyl‐2‐methyl‐6‐[6‐oxo‐1‐(3,7,11‐trimethyl‐dodeca‐2,6,10‐trienyl)‐1,6‐dihydro‐purin‐9‐yl]‐tetrahydro‐furo[3,4‐d][1,3]dioxol‐2‐yl}propionate (8 c) toward both human and rat glioblastoma cell lines in vitro.

Two series of nucleolipids, O-2',3'-heptanylidene- as well as O-2',3'-undecanylidene ketals of six β-d-ribonucleosides (type A) and partly N-farnesyl derivatives thereof (type B) were prepared in a combinatorial manner. All novel compounds were characterized by elemental analysis and/or ESI mass spectrometry and by UV-, H-, and C-NMR spectroscopy. Conformational parameters of the nucleosides and nucleolipids were calculated from various J(H,H), J( H, C), and J(F,H) coupling constants. For a drug profiling, the parent nucleosides and their lipophilic derivatives were studied with respect to their distribution (log P) between water and n-octanol as well as water and cyclohexane. From these data, qualitative conclusions were drawn concerning their possible blood-brain barrier passage efficiency. Moreover, nucleolipids were characterized by their molecular descriptor amphiphilic ratio (a.r.), which describes the balance between the hydrophilicity of the nucleoside headgroup and the lipophilicity of the lipid tail. All compounds were investigated in vitro with respect to their cytostatic/cytotoxic activity toward human glioblastoma (GOS 3) as well as rat malignant neuroectodermal BT4Ca cell lines in vitro. In order to differentiate between anticancer and side-effects of the novel nucleolipids, they were also studied on their activity on differentiated human THP-1 macrophages.

A series of nucleolipids, containing one of the β-D-ribonucleosides 5-fluorouridine, 6-azauridine, uridine, or 5-methyluridine were lipophilized, either at the O-2',3'-position and/or at N(3) of the nucleobase with a large variety of hydrophobic residues. The resulting nucleolipids as well as the parent nucleosides and the lipid precursors were investigated in vitro with respect to their antitumor activity towards i) ten human tumor cell lines from the NCI 60 panel and ii) partly against three further tumor cell lines, namely a) human astrocytoma/oligodendro glioma GOs-3, b) rat malignantneuroectodermal BT4Ca, and c) differentiated human THP-1 macrophages. Inspection of the doseresponse curves allows two main conclusions concerning lipid determinants lending the corresponding nucleoside an ameliorated or an acquired antitumor activity: i) introduction of either a symmetrical O-2',3'-nonadecylidene ketal group or introduction of an O-2',3'-ethyl levulinate moiety plus an N(3)-farnesyl group leads often to nucleolipids with significant cytostatic/cytotoxic properties; ii) for the two canonical and non-toxic nucleosides uridine and 5-methyluridine, the condensation with also non-toxic lipids gives nucleolipids with a pronounced antitumor activity.

Two lipophilic derivatives of formycin A (1) and formycin B (5) carrying an O‐2′,3′‐(ethyl levulinate) ketal group have been prepared. These were base‐alkylated at N(1) (for 1) and N(1) and N(6) (for 5) with both isopentenyl and all‐trans‐farnesyl residues. Upon the prenylation, side reactions were observed, resulting in the formation of nucleolipids with a novel tricyclic nucleobase (→4a, 4b). In the case of formycin B, O‐2′,3′‐(ethyl levulinate) (6) farnesylation gave the double prenylated nucleolipid 7. All new compounds were characterized by 1H‐, 13C‐, UV/VIS and fluorescence spectroscopy, by ESI‐MS spectrometry and/or by elemental analysis. Log P determinations between water and octanol as well as water and cyclohexane of a selection of compounds allowed qualitative conclusions concerning their potential blood‐brain barrier passage efficiency. All compounds were investigated in vitro with respect to their cytotoxic activity toward rat malignant neuroectodermal BT4Ca as well as against a series of human glioblastoma cell lines (GOS 3, U‐87 MG and GBM 2014/42). In order to differentiate between anticancer and side effects of the novel nucleolipids, we also studied their activity on PMA‐differentiated human THP‐1 macrophages. Here, we show that particularly the formycin A derivative 3b possesses promising antitumor properties in several cancer cell lines with profound cytotoxic effects partly on human glioblastoma cells, with a higher efficacy than the chemotherapeutic drug 5‐fluorouridine.