New thiazole hybrids were synthesized and evaluated for their in vitro cytotoxicity against a panel of human malignant cell lines. The key steps in the synthesis of hybrids 3-7 involved the initial condensation of appropriate aldononitriles with cysteine ethyl ester hydrochloride, followed by subsequent treatment of resulting thiazolines with DBU to form the thiazole ring. Bioiso-steres 8 and 14 have been prepared after the stereoselective addition of 2-(tri-methylsilyl)thiazole to the hemiacetals obtained by periodate cleavage of terminal diol functionality in the suitably protected D-glucose derivatives. The obtained analogues showed various antiproliferative activities in the cultures of several tumour cell lines. Hybrid 6 was the most potent in HeLa cells, exhibiting more than 10 and 4 times stronger activity than both leads 1 and 2, respectively. The most active compound in Raji cells was hybrid 12, which was nearly 2-fold more potent than the clinical antitumour drug doxorubicin. All analogues were more potent in A549 cells with respect to lead 1, while compounds 6 and 7 were slightly more active than DOX. Preliminary SAR analysis revealed that the presence of a cinnamate group at the C-3 position in analogues of type 7 increases the activity of resulting molecular hybrids.

(5R)-Cleistenolide and a few related analogues have been synthesized starting from d-glucose. The key steps of the synthesis included a Z-selective Wittig olefination and an intramolecular Mitsunobu reaction with an inversion of configuration at the C-5 position. In vitro antiproliferative activity of synthesized compounds was tested on a panel of eight human tumour cells and against a single normal cell line (MRC-5). The majority of tested compounds showed strong antiproliferative effects on certain human tumour cells and all of them showed negligible toxicity to normal foetal lung fibroblasts (MRC-5). The most active compound obtained in this work is lactone 5, which in MDA-MB 231 cell culture showed the same activity as doxorubicin (IC50 0.09 ?M). Strong antiproliferative activities of analogues 2, 5 and 6 were recorded in the K562 cell line (IC50 0.21, 0.34 and 0.33 ?M, respectively), in which they showed very similar activities to doxorubicin (IC50 0.25 ?M). A performed SAR study revealed that a change in the stereochemistry at the C-5 position may increase the activity of resulting stereoisomers.

Four novel conformationally restricted (?)-muricatacin analogues bearing a methoxy group at the C-5 position, with an alkoxymethyl group ?s the C-7 side chain, have been synthesised and their in vitro antiproliferative activity was evaluated against a panel of seven human tumour cell lines, as well as a single normal cell line. All analogues (9-12) showed diverse antiproliferative effects against all tested human malignant cell lines, but were devoid of any significant cytotoxicity towards the normal foetal lung fibroblasts (MRC-5). A SAR study reveals that the introduction of THF ring, exchange of C-8 methylene group in the side chain of muricatacin analogues with the O-8 ether functionality, as well as the length of side chain may be beneficial for the antiproliferative effects of these lactones. All novel analogues were more potent than lead compound, (?)-muricatacin, against HL-60 cell line.