Laulimalide is a potent, structurally unique microtubule-stabilizing agent originally isolated from the marine sponge Cacospongia mycofijiensis. Laulimalide exhibits an activity profile different from other microtubule-binding agents, notably including effectiveness against paclitaxel-resistant cells, but it is intrinsically unstable. Five analogues of laulimalide were designed to exhibit enhanced chemical stability yet retain its exceptional biological activities. Evaluations of these analogues showed that all are effective inhibitors of cancer-cell proliferation yet differ substantially in potency with an IC 50 range of 0.12-16.5 M. Although all of the analogues initiated cellular changes similar to laulimalide, including increased density of interphase microtubules, aberrant mitotic spindles, and ultimately apoptosis, differences among the analogues were apparent. The two most potent analogues, C 16-C17-des-epoxy laulimalide and C20-methoxy laulimalide, appear to have a mechanism of action identical to laulimalide. The C16-C17-des-epoxy, C20-methoxy laulimalide derivative, which incorporates both chemical changes of the most potent analogues, was significantly less potent and initiated the formation of unique interphase microtubules unlike the parent compound and other analogues. Two C2-C3-alkynoate derivatives had lower potency, and they initiated abnormal microtubule structures but did not cause micronucleation or extensive G2͞M accumulation. Significantly, paclitaxeland epothilone-resistant cell lines were less resistant to the laulimalide analogues. In summary, analogues of laulimalide designed to minimize or eliminate its intrinsic instability have been synthesized, and some have been found to retain the unique biological activities of laulimalide.antimitotics ͉ synthetic chemistry P aclitaxel (Taxol, Bristol-Myers Squibb), the first microtubule stabilizer identified, has proved to be of great value for the treatment of many types of cancer (1). The clinical successes of paclitaxel led to the development of a second-generation taxane, docetaxel (Taxotere, Aventis, Bridgewater, NJ), and initiated the intense search for other compounds with a similar mechanism of action. Several classes of structurally diverse microtubulestabilizing compounds have been identified. The first nontaxane stabilizers identified, the epothilones and discodermolide, had excellent preclinical activities and are being evaluated in clinical trials as anticancer agents.Laulimalide is a potent microtubule stabilizer that was originally isolated from the sponge Cacospongia mycofijiensis (2). Similar to the effects of other microtubule stabilizers, laulimalide increases the density of interphase microtubules and causes the formation of microtubule bundles and abnormal mitotic spindles, effects that culminate in mitotic arrest and initiation of apoptosis. Laulimalide stimulates the polymerization of bovine brain tubulin consistent with a direct interaction between the compound and tubulin (2, 3). Unlike the other stabilizers identified, ...
Prompted by our studies of transition metal-catalyzed [4+4], [4+2], [5+2], and [6+2] cycloadditions and by the view that these two-component reactions could be intercepted by a third component of one or more atoms, a new three-component transition metal-catalyzed cycloaddition is described. This new [5+2+1] cycloaddition proceeds in good to excellent yield and with high or complete regioselectivity with a variety of carbonyl-substituted alkynes to give bicyclo[3.3.0]octenone adducts, resulting from transannular closure of the intermediate eight-membered-ring cycloadduct. Effects of concentration, temperature, pressure, and catalyst loading on the efficiency of the reaction are discussed. This process provides access to complex building blocks for synthesis based on simple, readily available components.
Members of the BET family of bromodomain containing proteins have been identified as potential targets for blocking proliferation in a variety of cancer cell lines. A two-dimensional NMR fragment screen for binders to the bromodomains of BRD4 identified a phenylpyridazinone fragment with a weak binding affinity (1, K = 160 μM). SAR investigation of fragment 1, aided by X-ray structure-based design, enabled the synthesis of potent pyridone and macrocyclic pyridone inhibitors exhibiting single digit nanomolar potency in both biochemical and cell based assays. Advanced analogs in these series exhibited high oral exposures in rodent PK studies and demonstrated significant tumor growth inhibition efficacy in mouse flank xenograft models.
Prompted by the view that intermediates of transition metal-catalyzed reactions could be intercepted by one or more additional components, studies in our laboratory have led to the design and development of new three-component [5+2+1], [4+2+1], and [2+2+1] cycloadditions. These continuing studies have now led to the identification of a fundamentally new four-component [5+1+2+1] cycloaddition reaction of vinylcyclopropanes, alkynes and CO, yielding hydroxyindanone products in generally good yields. Terminal alkynes bearing aryl or alkyl groups are tolerated well. Substitution at any position of the VCP leads predictably to substituted hydroxyindanone products. Using a bis-alkynyl substrate, the reaction can be carried out bi-directionally, forming 10 C-C bonds and four new rings from seven components in a single, operationally simple process.
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