Synthesis and antitumor activity of 2'-bromo- and 2'-chloro-3'-acetoxy-3'-deaminodaunorubicin analogs

Halogen Atom Participation in Guiding the Stereochemical Outcomes of Acetal Substitution Reactions

Acetal substitution reactions of α-halogenated five- and six-membered rings can be highly stereoselective. Erosion of stereoselectivity occurs as nucleophilicity increases, which is consistent with additions to a halogen-stabilized oxocarbenium ion, not a three-membered-ring halonium ion. Computational investigations confirmed that the open-form oxocarbenium ions are the reactive intermediates involved. Kinetic studies suggest that hyperconjugative effects and through-space electrostatic interactions can both contribute to the stabilization of halogen-substituted oxocarbenium ions.

Synthesis and Preliminary Anticancer Activity Assessment of N-Glycosides of 2-Amino-1,3,4-thiadiazoles

The addition of 2-amino-1,3,4-thiadiazole derivatives with parallel iodination of differently protected glycals has been achieved using a double molar excess of molecular iodine under mild conditions. The corresponding thiadiazole derivatives of N-glycosides were obtained in good yields and anomeric selectivity. The usage of iodine as a catalyst makes this method easy, inexpensive, and successfully useable in reactions with sugars. Thiadiazole derivatives were tested in a panel of three tumor cell lines, MCF-7, HCT116, and HeLa. These compounds initiated biological response in investigated tumor models in a different rate. The MCF-7 is resistant to the tested compounds, and the cytometry assay indicated low increase in cell numbers in the sub- G1 phase. The most sensitive are HCT-116 and HeLa cells. The thiadiazole derivatives have a pro-apoptotic effect on HCT-116 cells. In the case of the HeLa cells, an increase in the number of cells in the sub-G1- phase and the induction of apoptosis was observed.

Inhibitory activity of four demethoxy fluorinated anthracycline analogs against five human-tumor cell lines

Four anthracycline analogs synthesized in our laboratory were evaluated in comparison with adriamycin (doxorubicin) for their growth-inhibitory effect against five human-tumor cell lines, including lung carcinoma, colon adenocarcinoma, breast adenocarcinoma, melanoma, and glioblastoma. The compounds included 4-demethoxy-7-O-(2,6-dideoxy-2-fluoro--l-talopyranosyl)daunomycinone (2), its 3',4'-diacetate (1), its 14-bromo derivative 3, and its 14-hydroxy analog, namely 4-demethoxy-7-O-(2,6-dideoxy-2-fluoro-α-l-talopyranosyl)adriamycinone (4). Compounds 1, 2, and 3 showed moderate cytotoxic effect in most of the cell lines, while compound 4 had a strong effect, comparable to or better than that of adriamycin in most of the cell lines.

Anthracycline glycosides of 2,6-dideoxy-2-fluoro-alpha-L-talopyranose

The methyl beta-glycoside of the title sugar, obtained from 2-deoxy-2-fluoro-beta-D-glucopyranose tetraacetate by a sequence with detailed characterization of all intermediates, was converted by acetolysis-bromination into 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl bromide, coupling of which with (7S,9S)-4-demethoxydaunomycinone afforded the 3,4-diacetate of 4-demethoxy-9-O-(2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl)daunomycinone (19). The antitumor-active 19 was converted by way of its 14-bromo derivative into the 14-hydroxy analogue, the antitumor-active 4-demethoxyadriamycinone glycoside 21.

Theoretical study of anthracycline antibiotic analogues--III. Conformational analysis on different 2, 6-dideoxy-2-halo-alpha-l-hexopyranoses by molecular mechanics and semiempirical methods

Conformational analysis of 2,6-dideoxy-2-halo-alpha-L-hexopyranoses (compounds 1-11) has been performed by molecular mechanics and molecular orbital calculations including solvation effects. The numerical results obtained and those obtained from the electrostatic potential calculation have been used together to interpret theoretically the influence of the introduction of the halogen atom at the C-2 position of the sugar moiety.

Design and tumor targeting of anthracyclines able to overcome multidrug resistance: a double-advantage approach

A novel, 'double-advantage approach' to developing more effective chemotherapies will be reviewed. This approach is based on a presumption that analogs designed on a sound hypothesis, and combined with a rationally selected drug delivery system, will optimize antitumor activity by creating drugs that are more active and that can be more specifically targeted to tumors. In the design of drugs superior to doxorubicin, we have focused on typical multidrug resistance and new anthracycline analogs, whose uptake is not affected by P-glycoprotein. Analysis of structural elements of anthracyclines affecting activity against multidrug resistant tumors and affinity for liposomes will be discussed. Annamycin, a lipophilic anthracycline analog, was selected for further preclinical development as a liposomal formulation and demonstrated, in the initial biological evaluation, high activity against tumors resistant to doxorubicin.

Iodoalkoxylation of 1,5-anhydro-2-deoxy-hex-1-enitols (glycals)

Exclusive trans-addition is observed in the iodoalkoxylation of the 6-membered cyclic enol ethers 3,4-di-O-acetyl-L-rhamnal (1), 3,4-di-O-acetyl-L-fucal (2), and related glycal derivatives. The main products from 1 and from 3,4,6-tri-O-acetyl-D-glucal (3) thus had the alpha-manno configuration. Similarly, alpha-talo products were obtained from 2 in 87-93% yield. The product distribution is not affected by the electronegativity of the 5-substituent. It is concluded that steric factors in the glycal and the nucleophile affect only the step of trans-diaxial opening of the intermediate iodonium ion. Enhanced yields of the desired trans-diaxial products were observed in reactions of glycals having the lyxo configuration when the reactions were conducted in tetrahydrofuran or methanol.

Synthesis of antitumor-active 7-O-(2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl)-daunomycinone and -adriamycinone

The title compounds (17 and 23) were prepared by coupling 3,4-di-O-acetyl-2,6-dideoxy-2-fluoro-alpha-L-talopyranosyl bromide (15) with daunomycinone. The key step in the preparation of 15 was the epoxide-ring opening of methyl 2,3-anhydro-4-O-benzyl-6-deoxy-alpha-L-gulopyranoside with KHF2 in ethylene glycol, whereupon 2-fluoro-alpha-L-idopyranoside was obtained. Compounds 17 and 23 showed strong antitumor activity.