ABSTRACT
Total synthesis of the Galbulimima alkaloid G. B. 13 was achieved utilizing a functionalized pyridine moiety as a piperidine surrogate. Key to the success of the synthesis was the development of an unprecedented rhodium-catalyzed 1,2-addition of an arylboronic ester into an unactivated ketone.
Subject(s)
Alkaloids/chemistry , Alkaloids/chemical synthesis , Ketones/chemistry , Pyridines/chemistry , Rhodium/chemistry , Boron/chemistry , Catalysis , Esters/chemistry , Models, Molecular , Molecular Conformation , Oxidation-Reduction , Piperidines/chemistryABSTRACT
A series of 13 anthrapyrazole compounds that are analogues of piroxantrone and losoxantrone were synthesized, and their cell growth inhibitory effects, DNA binding, topoisomerase IIalpha mediated (EC 5.99.1.3) cleavage of DNA, and inhibition of DNA topoisomerase IIalpha decatenation catalytic activities were determined. Cell growth inhibitory activity was well-correlated with DNA binding, suggesting that these compounds may act by targeting DNA. However, cell growth inhibition was not well-correlated with the inhibition of topoisomerase IIalpha catalytic activity, suggesting that these anthrapyrazoles did not act solely by inhibiting the catalytic activity of topoisomerase II. Most of the analogues were able to induce DNA cleavage, and thus, it was concluded that they acted, at least in part, as topoisomerase II poisons. Structure-based three-dimensional quantitative structure-activity analyses (3D-QSAR) were carried out on the aligned structures of the anthrapyrazoles docked into DNA using comparative molecular field analysis (CoMFA) and comparative molecular similarity index (CoMSIA) analyses in order to determine the structural features responsible for their activity. Both CoMFA and CoMSIA yielded statistically significant models upon partial least-squares analyses. The 3D-QSAR analyses showed that hydrogen-bond donor interactions and electrostatic interactions with the protonated amino side chains of the anthrapyrazoles led to high cell growth inhibitory activity.
Subject(s)
Anthraquinones/chemistry , Anthraquinones/pharmacology , Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Pyrazoles/chemistry , Pyrazoles/pharmacology , Pyrazolones/chemistry , Pyrazolones/pharmacology , Anthracyclines/chemistry , Antigens, Neoplasm/drug effects , DNA/chemistry , DNA/drug effects , DNA Topoisomerases, Type II/drug effects , DNA-Binding Proteins/drug effects , Models, Molecular , Nucleic Acid Conformation , Nucleic Acid Denaturation , Quantitative Structure-Activity RelationshipABSTRACT
Anthrapyrazoles have been investigated as cancer chemotherapeutic agents. The mechanism of action of these compounds is thought to involve inhibition of DNA topoisomerase II. A structure-activity study was carried out to determine the in vitro cytotoxic activity of nine novel anthrapyrazoles against human breast carcinoma, head and neck squamous cell carcinoma and leukemia cells, and against Chinese hamster ovary cells. The activity of these anthrapyrazole analogues was compared with that of two clinically tested anthrapyrazoles, losoxantrone and piroxantrone. Inhibition of topoisomerase II as a mechanism of action for the analogues was also investigated. The cytotoxic activity of the analogues was determined in vitro by MTT cell growth inhibition assay and inhibition of catalytic topoisomerase II activity by each compound was measured using a fluorometric DNA decatenation assay. All of the anthrapyrazole analogues inhibited the growth of the four cell lines with IC50 values that ranged from 0.1 to 45.2 microM. Losoxantrone was the most potent of the anthrapyrazole analogues studied. A tertiary amine in the basic side chain at N-2 increased the cytotoxic activity compared with a secondary amine in this side chain for many of the analogues, but not if there was a basic side chain at the C-5 position. A chlorine substituent on the basic side chain at N-2 did not have a consistent effect on activity. Moving the position of a chlorine substituent from C-5 to C-7 or introducing a basic side chain at C-5 did not have a consistent effect on cytotoxic activity. Anthrapyrazole analogues showed a broad range of activity for inhibiting topoisomerase II decatenation activity. Losoxantrone and piroxantrone were the most potent inhibitors of topoisomerase II activity. There was no significant correlation between the cytotoxic activity of the anthrapyrazole analogues and their ability to inhibit decatenation by topoisomerase II.
Subject(s)
Antineoplastic Agents/chemistry , Antineoplastic Agents/pharmacology , Topoisomerase II Inhibitors , Animals , Anthracyclines/chemistry , Anthracyclines/pharmacology , CHO Cells , Cricetinae , Cricetulus , DNA Topoisomerases, Type II/genetics , Drug Screening Assays, Antitumor , Humans , Inhibitory Concentration 50 , K562 Cells , Quantitative Structure-Activity RelationshipABSTRACT
[reaction: see text] A general set of conditions that achieves the union of aryl halides and divinyl or enyne carbinols to afford tri- or tetrasubstituted olefins in good yields (up to 83%) is described. The mechanism by which this proceeds is believed to involve the intermediacy of a cyclopropanol, followed by a novel skeletal reorganization. The ability to suppress beta-hydride elimination of organopalladium intermediates appears to be critical to the success of these processes.
ABSTRACT
The compact tricyclic substructure of solanoeclepin A containing the cyclobutanone ring was prepared by using as the key step a highly regioselective intramolecular [2 + 2]-photocycloaddition reaction between one of the [small pi]-bonds of an allene and the CC double bond of a butenolide.
