ABSTRACT
Modern methods for the identification of therapeutic leads include chemical or virtual screening of compound libraries. Nature's library represents a vast and diverse source of leads, often exhibiting exquisite biological activities. However, the advancement of natural product leads into the clinic is often impeded by their scarcity, complexity, and nonoptimal properties or efficacy as well as the challenges associated with their synthesis or modification. Function-oriented synthesis represents a strategy to address these issues through the design of simpler and therefore synthetically more accessible analogs that incorporate the activity-determining features of the natural product leads. This study illustrates the application of this strategy to the design and synthesis of functional analogs of the bryostatin marine natural products. It is specifically directed at exploring the activity-determining role of bryostatin A-ring functionality on PKC affinity and selectivity. The resultant functional analogs, which were prepared by a flexible, modular synthetic strategy, exhibit excellent affinity to PKC and differential isoform selectivity. These and related studies provide the basic information needed for the design of simplified and thus synthetically more accessible functional analogs that target PKC isoforms, major targets of therapeutic interest.
Subject(s)
Drug Design , Protein Kinase C/antagonists & inhibitors , Protein Kinase C/metabolism , Protein Kinase Inhibitors , Animals , Bryostatins/chemical synthesis , Bryostatins/chemistry , Bryostatins/pharmacology , CHO Cells , Cricetinae , Cricetulus , Drug Delivery Systems/methods , Humans , Isoenzymes/antagonists & inhibitors , Isoenzymes/genetics , Isoenzymes/metabolism , Mice , NIH 3T3 Cells , Protein Kinase C/genetics , Protein Kinase Inhibitors/chemical synthesis , Protein Kinase Inhibitors/chemistry , Protein Kinase Inhibitors/pharmacology , Protein Transport/drug effects , Protein Transport/geneticsABSTRACT
While beta-ketoesters are useful Michael donors, they were previously ineffective in Michael-Michael cascade reactions using alpha,beta-unsaturated aldehydes in conjunction with diphenylprolinol silyl ether organocatalysts. However, through rational modification of substrates and manipulation of the catalytic cycle, we developed an efficient Michael-Michael cascade reaction using beta-ketoesters of type 9. In this transformation, highly substituted fused carbocycles are generated in a single step in up to 87% yield and 99% ee.
Subject(s)
Combinatorial Chemistry Techniques , Ketones/chemistry , Polycyclic Aromatic Hydrocarbons/chemical synthesis , Catalysis , Cyclization , Cyclobutanes , Molecular Structure , Polycyclic Aromatic Hydrocarbons/chemistry , StereoisomerismABSTRACT
A new bifunctional organocatalyst with a novel structural and functional motif has been developed. This bifunctional sulfonamide organocatalyst was used in the conjugate addition of 1,3-dicarbonyl compounds (13) to ß-nitrostyrenes (12). Yields up to 91% and enantiomeric excesses up to 79% were obtained in this reaction. This catalyst activates both 13 via its basic moiety and 12 through hydrogen bonding.
ABSTRACT
5-Pyrrolidin-2-yltetrazole is a versatile organocatalyst for the asymmetric conjugate addition of nitroalkanes to enones. Using this catalyst, this transformation requires short reaction times, tolerates a broad substrate scope, and possibly proceeds via generation of an iminium species.
Subject(s)
Ketones/chemistry , Nitro Compounds/chemistry , CatalysisABSTRACT
5-Pyrrolidin-2-yltetrazole performs as an improved catalyst for the asymmetric addition of a range of nitroalkanes to cyclic and acyclic enones, with good to excellent enantioselectivity.
ABSTRACT
The functional properties of four diacylglycerol (DAG) analogues were compared using cell-signaling assays based on the protein RasGRP1, a DAG-regulated Ras activator. Compounds 1 and 2, synthetic analogues of bryostatin 1, were compared to authentic bryostatin 1 and phorbol 12-myristate-13-acetate (PMA). The two "bryologues" were able to activate RasGRP1 signaling rapidly in cultured cells and isolated mouse thymocytes. They elicited expression of the T cell activation marker CD69 in human T cells. DAG analogues promptly recruited RasGRP1 to cell membranes, but they did not induce RasGRP1 proteolysis. Bryostatin 1 and compounds 1 and 2 appeared to be less potent than PMA at inducing aggregation of mouse thymocytes, a PKC-dependent, RasGRP1-independent response. In addition to sharing potential anticancer properties with bryostatin 1, compounds 1 and 2 might be clinically useful as modulators of the immune system.
Subject(s)
DNA-Binding Proteins/physiology , Guanine Nucleotide Exchange Factors/physiology , Immunologic Factors/chemical synthesis , Lactones/chemical synthesis , Animals , Antigens, CD/biosynthesis , Antigens, Differentiation, T-Lymphocyte/biosynthesis , Bryostatins , Cell Aggregation/drug effects , Cell Membrane/metabolism , Cells, Cultured , DNA-Binding Proteins/genetics , Extracellular Signal-Regulated MAP Kinases/metabolism , Guanine Nucleotide Exchange Factors/genetics , Humans , Immunologic Factors/chemistry , Immunologic Factors/pharmacology , Lactones/chemistry , Lactones/pharmacology , Lectins, C-Type , Macrolides , Mice , Mutation , Phosphorylation , Protein Kinase C/physiology , Protein Transport/drug effects , Signal Transduction/drug effects , T-Lymphocytes/drug effects , T-Lymphocytes/metabolism , T-Lymphocytes/physiology , Tetradecanoylphorbol Acetate/pharmacology , Thymus Gland/cytology , TransfectionABSTRACT
Structurally simplified analogs of bryostatin 1, a marine natural product in clinical trials for the treatment of cancer, have been shown to be up to 50 times more potent than bryostatin 1 at inducing the translocation of PKCdelta-GFP from the cytosol of rat basophilic leukemia (RBL) cells. The end distribution of the protein is similar for all three compounds, despite a significant difference in translocation kinetics. The potency of the compounds for inducing the translocation response appears to be only qualitatively related to their binding affinity for PKC, highlighting the importance of using binding affinity in conjunction with real-time measurements of protein localization for the pharmacological profiling of biologically active agents.
Subject(s)
Antineoplastic Agents/pharmacology , Green Fluorescent Proteins/metabolism , Lactones/pharmacology , Protein Kinase C/metabolism , Recombinant Fusion Proteins/metabolism , Animals , Antineoplastic Agents/chemistry , Bryostatins , Cell Line, Tumor , Dose-Response Relationship, Drug , Endocytosis/drug effects , Kinetics , Lactones/chemistry , Macrolides , Microscopy, Confocal , Microscopy, Fluorescence , Molecular Structure , Rats , Structure-Activity RelationshipABSTRACT
Bryostatin 1 represents a novel and potent therapeutic lead with a unique activity profile. Its natural and synthetic availability is severely limited. Function oriented synthesis provides a means to address this supply problem through the design of synthetically more accessible simplified structures that at the same time incorporate improved functional activity. Pharmacophore searching and a new computer aided visualization of a possible binding mode are combined with an understanding of function and knowledge of synthesis to design and prepare a new and simplified compound with bryostatin-like function in biological systems. This new compound is a potent ligand for protein kinase C in vitro (K(i) = 8.0 nM). More significantly, the described molecule retains the functional ability to translocate a PKCdelta-GFP fusion protein in RBL cells. The extent of protein translocation and the sub-cellular localization induced by this new compound is similar to that seen in response to bryostatin 1, indicating that the new molecule retains the functional activity of the natural product but is simpler and can be synthesized in a practical fashion.
Subject(s)
Drug Design , Macrolides/chemical synthesis , Macrolides/pharmacology , Protein Kinase C/metabolism , Animals , Bryostatins , Cell Line, Tumor , Image Processing, Computer-Assisted , Indicators and Reagents , Isoenzymes/chemistry , Isoenzymes/metabolism , Leukemia, Basophilic, Acute/drug therapy , Leukemia, Basophilic, Acute/metabolism , Macrolides/metabolism , Microscopy, Fluorescence , Models, Molecular , Protein Binding , Protein Kinase C/chemistry , RatsABSTRACT
Macrocycle 1 is a new highly potent analogue of bryostatin 1, a promising anti-cancer agent currently in human clinical trials. In vitro, 1 displays picomolar affinity for PKC and exhibits over 100-fold greater potency than bryostatin 1 when tested against various human cancer cell lines. Macrocycle 1 can be generated in clinically required amounts by chemical synthesis in only 19 steps (LLS) and represents a new clinical lead for the treatment of cancer.
