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The synthesis and the X-ray structure of 16a-thiocamptothecin (TCPT), the thiopyridone analog of camptothecin (CPT), are accomplished. The crystal contains two structurally identical, yet independent molecules. Both of them are connected to other molecules via two intermolecular hydrogen bonds. S-methylation of TCPT leads to the cleavage of the C-ring. The cytotoxic activity of TCPT was evaluated against different human tumor cell lines using CPT as reference compound.

New 3-O-glycosyl-3-demethylthiocolchicines containing natural and unnatural sugar moieties were prepared and tested on gamma-aminobutyric acid (GABA) and strychnine-sensitive glycine receptors present in rat brain and spinal cord. Two different synthetic approaches were used with the readily available 3-O-demethylthiocolchicine (1b) and thiocolchicoside (2a). Glycosyl compounds 2a-g were obtained from 1b and 1-fluorosugars 4. 6'-Heterosubstituted glycosyl compounds 6-12 and the 6'-desoxy derivative 2h were prepared from 2a.

A novel class of 3-demethoxy-3-glycosylaminothiocolchicines (7) was prepared and tested for muscle relaxant activity. The syntheses were performed starting from the new 3-amino-3-demethoxythiocolchicine (5) prepared in good yield from 3-O-demethylthiocolchicine (1c) using the Buchwald-Hartwig reaction. The condensation of 5 with a series of pentose and hexose sugars (6) gave a series of 3-demethoxy-3-glycosylaminothiocolchicines (7). Their preparation was accomplished by adapting and improving a previous procedure for the preparation of N-arylglycosylamines. In particular, replacing traditional heating with microwave irradiation represents the key improvement of the process. The biological activity of the 3-demethoxy-3-glycosylaminothiocolchicines (7) was evaluated on GABA and strychnine-sensitive glycine receptors present in rat brain and spinal cord.

A diverse range of chromen-2-one, chromen-4-one and pyrimidoisoquinolin-4-one derivatives was synthesized and evaluated for inhibitory activity against the DNA repair enzyme DNA-dependent protein kinase (DNA-PK), with a view to elucidating structure-activity relationships for potency and kinase selectivity. DNA-PK inhibitory activity varied widely over the series of compounds evaluated (IC(50) values ranged from 0.19 to10 microM), with excellent activity being observed for the 7,8-benzochromen-4-one and pyrimido[2,1-a]isoquinolin-4-one templates. By contrast, inhibitors based on the benzochromen-2-one (coumarin) or 2-aryl-7,8-benzochromen-4-one (flavone) scaffolds were less potent. Crucially, these studies revealed a very constrained structure-activity relationship at the 2-position of the benzopyranone and pyrimido[2,1-a]isoquinolin-4-one pharmacophore, with only a 2-morpholino or 2-(2'-methylmorpholino) group being tolerated at this position. More detailed biological studies conducted with the most potent inhibitor NU7163 (48; IC(50) = 0.19 microM) demonstrated ATP-competitive DNA-PK inhibition, with a K(i) value of 24 nM, and 48 exhibited selectivity for DNA-PK compared with the related enzymes ATM, ATR, mTOR, and PI 3-K (p110alpha). Compound 48 sensitized the HeLa human tumor cell line to the cytotoxic effects of ionizing radiation in vitro, a dose modification factor of 2.3 at 10% survival being observed with an inhibitor concentration of 5 microM. This study identified these structural classes as novel DNA-PK inhibitors and delineated initial structure-activity relationships against DNA-PK.

A series of 2'-methyl taxoids were synthesized and essayed for growth inhibition experiments conducted in human ovarian cancer cell line A2780wt and its counterparts A2780cis, A2780tax, and A2780adr, resistant to cisplatin, paclitaxel, and doxorubicin, respectively, to test the effect of this substituent on the antitumor activity. Additional experiments were performed on MCF-7 human breast cancer cell line and MCF7-R resistant to doxorubicin. In several cases these taxoids were more active than paclitaxel showing subnanomolar IC(50) values.