RESUMO
Important strides are being made in understanding the effects of structural features of bryostatinâ 1, a candidate therapeutic agent for cancer and dementia, in conferring its potency toward protein kinaseâ C and the unique spectrum of biological responses that it induces. A critical pharmacophoric element in bryostatinâ 1 is the secondary hydroxy group at the C26 position, with a corresponding primary hydroxy group playing an analogous role in binding of phorbol esters to protein kinase C. Herein, we describe the synthesis of a bryostatin homologue in which the C26 hydroxy group is primary, as it is in the phorbol esters, and show that its biological activity is almost indistinguishable from that of the corresponding compound with a secondary hydroxy group.
Assuntos
Briostatinas/química , Briostatinas/farmacologia , Desenho de Fármacos , Proteína Quinase C/antagonistas & inibidores , Inibidores de Proteínas Quinases/química , Inibidores de Proteínas Quinases/farmacologia , Animais , Briostatinas/síntese química , Briostatinas/farmacocinética , Linhagem Celular Tumoral , Humanos , Metilação , Camundongos , Proteína Quinase C/metabolismo , Inibidores de Proteínas Quinases/síntese química , Inibidores de Proteínas Quinases/farmacocinética , Relação Estrutura-AtividadeRESUMO
To investigate the cellular distribution of tumor-promoting vs. non-tumor-promoting bryostatin analogues, we synthesized fluorescently labeled variants of two bryostatin derivatives that have previously shown either phorbol ester-like or bryostatin-like biological activity in U937 leukemia cells. These new fluorescent analogues both displayed high affinity for protein kinaseâ C (PKC) binding and retained the basic properties of the parent unlabeled compounds in U937 assays. The fluorescent compounds showed similar patterns of intracellular distribution in cells, however; this argues against an existing hypothesis that various patterns of intracellular distribution are responsible for differences in biological activity. Upon further characterization, the fluorescent compounds revealed a slow rate of cellular uptake; correspondingly, they showed reduced activity for cellular responses that were only transient upon treatment with phorbol ester or bryostatinâ 1.
Assuntos
Briostatinas/química , Corantes Fluorescentes/química , Humanos , Ésteres de Forbol/química , Ligação Proteica , Proteína Quinase C/metabolismo , Células U937RESUMO
Bryostatin 1, a complex macrocyclic lactone, is the subject of multiple clinical trials for cancer chemotherapy. Although bryostatin 1 biochemically functions like the classic mouse skin tumor promoter phorbol 12-myristate 13-acetate (PMA) to bind to and activate protein kinase C, paradoxically, it fails to induce many of the typical phorbol ester responses, including tumor promotion. Intense synthetic efforts are currently underway to develop simplified bryostatin analogs that preserve the critical functional features of bryostatin 1, including its lack of tumor promoting activity. The degree to which bryostatin analogs maintain the unique pattern of biological behavior of bryostatin 1 depends on the specific cellular system and the specific response. Merle 23 is a significantly simplified bryostatin analog that retains bryostatin like activity only to a limited extent. Here, we show that in mouse epidermal cells the activity of Merle 23 was either similar to bryostatin 1 or intermediate between bryostatin 1 and PMA, depending on the specific parameter examined. We then examined the hyperplastic and tumor promoting activity of Merle 23 on mouse skin. Merle 23 showed substantially reduced hyperplasia and was not tumor promoting at a dose comparable to that for PMA. These results suggest that there may be substantial flexibility in the design of bryostatin analogs that retain its lack of tumor promoting activity. © 2016 Wiley Periodicals, Inc.
Assuntos
Antineoplásicos/farmacologia , Briostatinas/farmacologia , Queratinócitos/efeitos dos fármacos , Neoplasias Cutâneas/induzido quimicamente , Neoplasias Cutâneas/tratamento farmacológico , Animais , Desenho de Fármacos , Epiderme/efeitos dos fármacos , Epiderme/metabolismo , Epiderme/patologia , Feminino , Queratinócitos/metabolismo , Queratinócitos/patologia , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos SENCAR , Ésteres de Forbol/farmacologia , Proteína Quinase C/metabolismo , Neoplasias Cutâneas/metabolismo , Neoplasias Cutâneas/patologiaRESUMO
As an initial step in designing a simplified bryostatin hybrid molecule, three bryostatin analogues bearing a diacylglycerol lactone-based C-ring, which possessed the requisite pharmacophores for binding to protein kinase C (PKC) together with a modified bryostatin-like A- and B-ring region, were synthesized and evaluated. Merle 46 and Merle 47 exhibited binding affinity to PKC alpha with Ki values of 7000 ± 990 and 4940 ± 470 nM, respectively. Reinstallation of the trans-olefin and gem-dimethyl group present in bryostatin 1 in Merle 48 resulted in improved binding affinity, 363 ± 42 nM. While Merle 46 and 47 were only marginally active biologically, Merle 48 showed sufficient activity on the U937 cells to confirm that it was PMA-like for growth and attachment, as predicted by the substitution pattern of its A- and B-rings.
Assuntos
Briostatinas/síntese química , Briostatinas/farmacologia , Diglicerídeos/química , Lactonas/química , Briostatinas/metabolismo , Espectroscopia de Ressonância Magnética Nuclear de Carbono-13 , Proteína Quinase C/metabolismo , Espectroscopia de Prótons por Ressonância Magnética , Espectrometria de Massas por Ionização por Electrospray , Especificidade por SubstratoRESUMO
We describe a convergent synthesis of a bryostatin analogue in which the natural A- and B-ring pyrans have been replaced by phenyl rings. The new analogue exhibited PMA like behavior in cell assays, but failed to maintain high affinity binding for PKC, despite retaining an unaltered C-ring 'binding domain'.
RESUMO
Bryostatin 1, a complex macrocyclic lactone isolated from Bugula neritina, has been the subject of multiple clinical trials for cancer. Although it functions as an activator of protein kinase C (PKC) in vitro, bryostatin 1 paradoxically antagonizes most responses to the prototypical PKC activator, the phorbol esters. The bottom half of the bryostatin 1 structure has been shown to be sufficient to confer binding to PKC. In contrast, we have previously shown that the top half of the bryostatin 1 structure is necessary for its unique biological behavior to antagonize phorbol ester responses. Neristatin 1 comprises a top half similar to that of bryostatin 1 together with a distinct bottom half that confers PKC binding. We report here that neristatin 1 is bryostatin 1-like, not phorbol ester-like, in its biological activity on U937 promyelocytic leukemia cells. We conclude that the top half of the bryostatin 1 structure is largely sufficient for bryostatin 1-like activity, provided the molecule also possesses an appropriate PKC binding domain.
Assuntos
Briostatinas/química , Briozoários/química , Proteína Quinase C/efeitos dos fármacos , Animais , Humanos , Modelos Moleculares , Estrutura Molecular , Ésteres de Forbol , Proteína Quinase C/metabolismoRESUMO
A convergent synthesis of a des-B-ring bryostatin analogue is described. This analogue was found to undergo an unexpected ring expansion of the bryolactone core to generate the corresponding 21-membered macrocycle. The parent analogue and the ring-expanded product both displayed nanomolar binding affinity for PKC. Despite containing A-ring substitution identical to that of bryostatin 1 and displaying bryostatin-like biological function, the des-B-ring analogues displayed a phorbol-like biological function in cells. These studies shed new light on the role of the bryostatin B-ring in conferring bryo-like biological function to bryostatin analogues.
Assuntos
Antineoplásicos/química , Produtos Biológicos/química , Briostatinas/química , Briozoários/química , Animais , Antineoplásicos/síntese química , Antineoplásicos/farmacologia , Produtos Biológicos/síntese química , Produtos Biológicos/farmacologia , Briostatinas/síntese química , Briostatinas/farmacologia , Linhagem Celular Tumoral , Humanos , Modelos Moleculares , Forbóis/farmacologia , Proteína Quinase C/metabolismoRESUMO
The role of the C(8) gem-dimethyl group in the A-ring of bryostatin 1 has been examined through chemical synthesis and biological evaluation of a new analogue. Assays for biological function using U937, K562, and MV4-11 cells as well as the profiles for downregulation of PKC isozymes revealed that the presence of this group is not a critical determinant for the unique pattern of biological activity of bryostatin.
Assuntos
Antineoplásicos/síntese química , Briostatinas/síntese química , Proteína Quinase C/antagonistas & inibidores , Antineoplásicos/farmacologia , Briostatinas/farmacologia , Adesão Celular/efeitos dos fármacos , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Regulação para Baixo , Humanos , Isoenzimas/antagonistas & inibidores , Isoenzimas/metabolismo , Estrutura Molecular , Proteína Quinase C/metabolismo , Relação Estrutura-Atividade , Acetato de Tetradecanoilforbol/farmacologiaRESUMO
Bryostatin 1 is a marine natural product that is a very promising lead compound because of the potent biological activity it displays against a variety of human disease states. We describe herein the first total synthesis of this agent. The synthetic route adopted is a highly convergent one in which the preformed, heavily functionalized pyran rings A and C are united by "pyran annulation", the TMSOTf-promoted reaction between a hydroxyallylsilane appended to the A-ring fragment and an aldehyde contained in the C-ring fragment, with concomitant formation of the B ring. Further elaborations of the resulting very highly functionalized intermediate include macrolactonization and selective cleavage of just one of five ester linkages present.
Assuntos
Briostatinas/síntese química , Produtos Biológicos/síntese química , Produtos Biológicos/química , Briostatinas/química , Piranos/química , EstereoisomerismoRESUMO
Phorbol 12-myristate 13-acetate (PMA) and bryostatin 1 are both potent protein kinase C (PKC) activators. In LNCaP human prostate cancer cells, PMA induces tumor necrosis factor alpha (TNFα) secretion and inhibits proliferation; bryostatin 1 does not, and indeed blocks the response to PMA. This difference has been attributed to bryostatin 1 not localizing PKCδ to the plasma membrane. Since phorbol ester lipophilicity influences PKCδ localization, we have examined in LNCaP cells a series of phorbol esters and related derivatives spanning some eight logs in lipophilicity (logP) to see if any behave like bryostatin 1. The compounds showed marked differences in their effects on proliferation and TNFα secretion. For example, maximal responses for TNFα secretion relative to PMA ranged from 97 % for octyl-indolactam V to 24 % for phorbol 12,13-dibenzoate. Dose-response curves ranged from monophasic for indolactam V to markedly biphasic for sapintoxin D. The divergent patterns of response, however, correlated neither to lipophilicity, to plasma membrane translocation of PKCδ, nor to the ability to interact with model membranes. In U937 human leukemia cells, a second system in which PMA and bryostatin 1 have divergent effects, viz. PMA but not bryostatin 1 inhibits proliferation and induces attachment, all the compounds acted like PMA for proliferation, but several induced a reduced level or a biphasic dose-response curve for attachment. We conclude that active phorbol esters are not all equivalent. Depending on the system, some might partially resemble bryostatin 1 in their behavior; this encourages the concept that bryostatin-like behavior may be obtained from other structural templates.
Assuntos
Antineoplásicos/farmacologia , Briostatinas/farmacologia , Ésteres de Forbol/farmacologia , Linhagem Celular Tumoral , Proliferação de Células/efeitos dos fármacos , Relação Dose-Resposta a Droga , Humanos , Concentração Inibidora 50 , Leucemia/patologia , Masculino , Estrutura Molecular , Neoplasias da Próstata/patologiaRESUMO
Highly potent bryostatin analogues which contain the complete bryostatin core structure have been synthesized using a pyran annulation approach as a key strategic element. The A ring pyran was assembled using a pyran annulation reaction between a C1-C8 hydroxy allylsilane and an aldehyde comprising C9-C13. This pyran was transformed to a new hydroxy allylsilane and then coupled with a preformed C ring aldehyde subunit in a second pyran annulation, with concomitant formation of the B ring. This tricyclic intermediate was elaborated to bryostatin analogues which displayed nanomolar to subnanomolar affinity for PKC, but displayed properties indistinguishable from a phorbol ester in a proliferation/attachment assay.
Assuntos
Briostatinas/síntese química , Piranos/química , Acetato de Tetradecanoilforbol/química , Materiais Biomiméticos/síntese química , Materiais Biomiméticos/química , Briostatinas/químicaRESUMO
Studies leading to a total synthesis of epothilones B and D are described. The overall synthetic plan was based on late-stage fragment assembly of two segments representing C(1)-C(9) and C(10)-C(21) of the structure. The C(1)-C(9) fragment was prepared by elaboration of commercially available (2R)-3-hydroxy-2-methylpropanoate at both ends of the three-carbon unit. Introduction of carbons 1-4 containing the gem-dimethyl unit was achieved in a convergent manner using a diastereoselective addition of a stannane equivalent of a beta-keto ester dianion. An enantioselective addition of such a stannane equivalent for a beta-keto ester dianion was also used to fashion one version of the C(10)-C(21) subunit; however, the fragment assembly (using bimolecular esterification followed by ring-closing metathesis) with this subunit failed. Therefore, fragment assembly was achieved using a Wittig reaction; this was followed by macrolactonization to close the macrocycle. The C(10)-C(21) subunit needed for this approach was prepared in an efficient manner using the Corey-Kim reaction as a key element. Other key reactions in the synthesis include a stereoselective SmI(2) reduction of a beta-hydroxy ketone and a critical opening of a valerolactone with aniline which required extensive investigation.
Assuntos
Antineoplásicos/síntese química , Epotilonas/síntese química , Álcoois/química , Ânions/química , Ácidos Carboxílicos/síntese química , Ésteres/química , Indicadores e Reagentes , Lactonas/química , Espectroscopia de Ressonância MagnéticaRESUMO
A new convergent synthetic approach to a pyran motif common to many naturally occurring structures is described. In this approach, two fragments are joined by esterification, and a subsequent intramolecular reductive cyclization affords the 2-hydroxypyran.
Assuntos
Piranos/química , Acilação , Briostatinas , Ciclização , Compostos Heterocíclicos/química , Macrolídeos/química , Estrutura Molecular , Oxirredução , Piranos/síntese químicaRESUMO
A vinylogous Mukaiyama aldol reaction, conducted using 10 mol % of a BITIP catalyst and B(OMe)3 as an additive, effects an enantioselective four-carbon chain extension to give versatile E-alpha,beta-unsaturated thiol esters.
Assuntos
Compostos de Boro/síntese química , Compostos de Sulfidrila/síntese química , Compostos de Boro/química , Catálise , Técnicas de Química Combinatória , Ésteres , Estrutura Molecular , Estereoisomerismo , Compostos de Sulfidrila/químicaRESUMO
[reaction: see text] The synthesis of a C1-C13 A-ring subunit of bryostatin 1 is detailed. The key features of the approach include the convergent fragment assembly with a highly stereoselective construction of the C7-C8 bond indicated above.
Assuntos
Macrolídeos/síntese química , Animais , Briostatinas , Briozoários/química , Macrolídeos/química , Estrutura MolecularRESUMO
An expeditious assembly of a C(1)-C(16) subunit of bryostatin 1 is described. A pyran annulation reaction was utilized to form the B-ring by reaction of a hydroxy-allylsilane with a fully elaborated A-ring subunit. This annulation process proceeded with complete diastereoselectivity and in excellent isolated yield despite the presence of potentially sensitive functionality in the A-ring segment.
RESUMO
[reaction: see text]. A synthesis of a potential BC-ring subunit (C9-C27) for bryostatin 1, a remarkably potent anticancer agent, has been developed in 16 steps and 18% overall yield. The key features of this route include a BITIP-catalyzed asymmetric allylation reaction, chelation-controlled allylations, a hydroformylation reaction, and a pyran annulation reaction.
Assuntos
Antineoplásicos/química , Antineoplásicos/síntese química , Macrolídeos/química , Macrolídeos/síntese química , Piranos/química , Briostatinas , Catálise , Estrutura MolecularRESUMO
[reaction: see text]. Synthesis of the first of a projected series of bryostatin analogues has been accomplished in 26 steps and 2.2% overall yield. In this letter, we detail two approaches to the structural core of these tricyclic macrolactone bryostatin analogues. The key features of the route include BITIP-catalyzed asymmetric allylation reactions and Mukaiyama aldol reactions, a chelation-controlled allylation, pyran annulation reactions, and macrolactonization.
Assuntos
Antineoplásicos/química , Antineoplásicos/síntese química , Lactonas/química , Lactonas/síntese química , Macrolídeos/química , Macrolídeos/síntese química , Piranos/química , Briostatinas , Catálise , Ciclização , Estrutura MolecularRESUMO
[reaction: see text] The development of an approach leading to the total synthesis of dactylolide is described. The key features of this route include a catalytic asymmetric allylation, a diastereoselective pyran annulation, and a Horner-Wadsworth-Emmons macrocyclization.
Assuntos
Antineoplásicos/síntese química , Compostos Bicíclicos Heterocíclicos com Pontes/síntese química , Lactonas/síntese química , Animais , Antineoplásicos/química , Compostos Bicíclicos Heterocíclicos com Pontes/química , Lactonas/química , Estrutura Molecular , Poríferos/química , EstereoisomerismoRESUMO
The efficient construction of the C(1)-C(13) segment of dolabelide B is described. A key element of the synthesis entails BITIP catalyzed asymmetric methallylation to establish the C(7) stereocenter, which was then used to direct the stereoselective installation of the C(9) and C(11) centers through Evans reduction and 1,5-anti aldol condensation, respectively.