Synthetic study on curacin A: A novel antimitotic agent from the cyanobacterium Lyngbya majuscula

Functionalised bicyclic tetramates derived from cysteine as antibacterial agents

Routes to bicyclic tetramates derived from cysteine permitting ready incorporation of functionality at two different points around the periphery of a heterocyclic skeleton are reported. This has enabled the identification of systems active against Gram-positive bacteria, some of which show gyrase and RNA polymerase inhibitory activity. In particular, tetramates substituted with glycosyl side chains, chosen to impart polarity and aqueous solubility, show high antibacterial activity coupled with modest gyrase/polymerase activity in two cases. An analysis of physicochemical properties indicates that the antibacterially active tetramates generally occupy physicochemical space with MW of 300-600, clog D7.4 of -2.5 to 4 and rel. PSA of 11-22%. This work demonstrates that biologically active 3D libraries are readily available by manipulation of a tetramate skeleton.

Synthetic and structure-activity relationship studies on bioactive natural products

This review summarizes our research into the synthesis and structure-activity relationships of epolactaene, neoechinulin A, plakevulin A, pseudodeflectusin and ustusorane C. These natural products are attractive in view of their apoptosis-inducing activity, cytoprotective activity against peroxynitrite, inhibitory activity against DNA polymerases, and cytotoxicity in cancer cells.

Farnesyloxycoumarins, a new class of squalene-hopene cyclase inhibitors

A few naturally occurring prenyl- and prenyloxycoumarins and several new related synthetic derivatives were evaluated as inhibitors of squalene-hopene cyclase (SHC), a useful model enzyme, to predict their interactions with oxidosqualene cyclase (OSC). Umbelliprenin-10',11'-monoepoxide (IC(50) 2.5 microM) and the corresponding 6',7'-10',11' diepoxide (IC(50) 1.5 microM) were the most active enzyme inhibitors.

Kinetics of the epoxidation of geraniol and model systems by dimethyldioxirane

The mono-epoxidation of geraniol by dimethyldioxirane was carried out in various solvents. In all cases, the product ratios for the 2,3 and 6,7 mono-epoxides were in agreement with literature values. Kinetic studies were carried out at 23 degrees C in the following dried solvent systems: acetone (k(2) = 1.49 M(-1)s(-1)), carbon tetrachloride/acetone(9/1, k(2)=2.19 M(-1)s(-1)), and methanol/acetone (9/1, k(2) = 17 M(-1)s(-1)). Individual k(2) values were calculated for epoxidation of the 2,3 and 6,7 positions in geraniol. The non-conjugated diene system was modeled employing two simple independent alkenes:2-methyl-2-pentene and 3-methyl-2-buten-1-ol by determining the respective k(2) values for epoxidation in various solvents. The kinetic results for each independent alkene showed that the relative reactivity of the two epoxidation sites in geraniol as a function of solvent was not simply a summation of the independent alkene systems.

Synthesis of thiazolines linked to a difluoromethylphosphonate diester via dithioester chemistry

[reaction: see text] A two-step, high-yielding synthesis of delta(2)-thiazolines containing a difluoromethylphosphonate diester moiety has been devised using a building block approach. Racemic or chiral beta-amino alcohols and diols were coupled with methyl difluoro(diethoxyphosphono)dithioacetate to give predominantly the corresponding beta-hydroxythioamides, which were then cyclized to provide a series of novel substituted delta(2)-thiazolines.

Structure-activity analysis of the interaction of curacin A, the potent colchicine site antimitotic agent, with tubulin and effects of analogs on the growth of MCF-7 breast cancer cells

Originally purified as a major lipid component of a strain of the cyanobacterium Lyngbya majuscula isolated in Curaçao, curacin A is a potent inhibitor of cell growth and mitosis, binding rapidly and tightly at the colchicine site of tubulin. Because its molecular structure differs so greatly from that of colchicine and other colchicine site inhibitors, we prepared a series of curacin A analogs to determine the important structural features of the molecule. These modifications include reduction and E-to-Z transitions of the olefinic bonds in the 14-carbon side chain of the molecule; disruption of and configurational changes in the cyclopropyl moiety; disruption, oxidation, and configurational reversal in the thiazoline moiety; configurational reversal and substituent modifications at C13; and demethylation at C10. Inhibitory effects on tubulin assembly, the binding of colchicine to tubulin, and the growth of MCF-7 human breast carcinoma cells were examined. The most important portions of curacin A required for its interaction with tubulin seem to be the thiazoline ring and the side chain at least through C4, the portion of the side chain including the C9-C10 olefinic bond, and the C10 methyl group. Only two modifications totally eliminated the tubulin-drug interaction. The inactive compounds were a segment containing most of the side chain, including its two substituents, and analogs in which the methyl group at the C13 oxygen atom was replaced by a benzoate residue. Antiproliferative activity comparable with that observed with curacin A was only reproduced in compounds that were potent inhibitors of the binding of colchicine to tubulin. Molecular modeling and quantitative structure-activity relationship studies demonstrated that most active analogs overlapped extensively with curacin A but failed to provide an explanation for the apparent structural analogy between curacin A and colchicine.