A Pd-H/Isothiourea Cooperative Catalysis Approach to anti-Aldol Motifs: Enantioselective α-Alkylation of Esters with Oxyallenes

The biological and therapeutic significance of natural products is a powerful impetus for the development of efficient methods to facilitate their construction. Accordingly, and reflecting the prevalence of β-oxy-carbonyl motifs, a sophisticated arsenal of aldol-based strategies has evolved that is contingent on the generation of single enolate isomers. Since this has the potential to compromise efficiency in reagent-based paradigms, direct catalysis-based solutions would be enabling. To complement the array of substrate-based strategies, and regulate enolate geometry at the catalyst level, a direct catalytic alkylation of esters with oxyallenes has been developed. Synergizing metal hydride reactivity with Lewis base catalysis has resulted in a broad reaction scope with useful levels of stereocontrol (up to >99 % ee). Facile derivatization of these ambiphilic linchpins is demonstrated, providing access to high-value vicinal stereocenter-containing motifs, including 1,2-amino alcohols.

A Comparative Study of High-Contrast Fluorescence Lifetime Probes for Imaging Amyloid in Tissue

Optical imaging of protein aggregates in living and post-mortem tissue can often be impeded by unwanted fluorescence, prompting the need for novel methods to extract meaningful signal in complex biological environments. Historically, benzothiazolium derivatives, prominently Thioflavin T, have been the state-of-the-art fluorescent probes for amyloid aggregates, but their optical, structural, and binding properties typically limit them to in vitro applications. This study compares the use of novel uncharged derivative, PAP_1, with parent Thioflavin T as a fluorescence lifetime imaging probe. This is applied specifically to imaging recombinant α-synuclein aggregates doped into brain tissue. Despite the 100-fold lower brightness of PAP_1 compared to that of Thioflavin T, PAP_1 binds to α-synuclein aggregates with an affinity several orders of magnitude greater than Thioflavin T; thus, we observe a specific decrease in the fluorescence lifetime of PAP_1 bound to α-synuclein aggregates, resulting in a separation of >1.4 standard deviations between PAP_1-stained brain tissue background and α-synuclein aggregates that is not observed with Thioflavin T. This enables contrast between highly fluorescent background tissue and amyloid fibrils that is attributed to the greater affinity of PAP_1 for α-synuclein aggregates, avoiding the substantial off-target staining observed with Thioflavin T.

A Comparative Photophysical Study of Structural Modifications of Thioflavin T-Inspired Fluorophores

The benzothiazolium salt, Thioflavin T (ThT), has been widely adopted as the "gold-standard" fluorescent reporter of amyloid in vitro. Its properties as a molecular rotor result in a large-scale (∼1000-fold) fluorescence turn-on upon binding to β-sheets in amyloidogenic proteins. However, the complex photophysics of ThT combined with the intricate and varied nature of the amyloid binding motif means these interactions are poorly understood. To study this important class of fluorophores, we present a detailed photophysical characterization and comparison of a novel library of 12 ThT-inspired fluorescent probes for amyloid protein (PAPs), where both the charge and donor capacity of the heterocyclic and aminobenzene components have been interrogated, respectively. This enables direct photophysical juxtaposition of two structural groups: the neutral "PAP" (class 1) and the charged "mPAP" fluorophores (class 2). We quantify binding and optical properties at both the bulk and single-aggregate levels with some derivatives showing higher aggregate affinity and brightness than ThT. Finally, we demonstrate their abilities to perform super-resolution imaging of α-synuclein fibrils with localization precisions of ∼16 nm. The properties of the derivatives provide new insights into the relationship between chemical structure and function of benzothiazole probes.

Tertiary Amine Lewis Base Catalysis in Combination with Transition Metal Catalysis

The cooperation between two orthogonal catalytic events during the formation of carbon-carbon and carbon-heteroatom bonds has emerged as an effective strategy for enantioselective chemical synthesis. In recent years, a number of pioneering investigations have described useful chemical synthesis methods whereby the reactivity or nucleophile-electrophile combinations can be fine-tuned or extended far beyond the effect and influence of a single catalyst. The recognition of this has had profound implications for the development cooperative catalysis as a field and has provided a foundation for the development of broadly useful chemical synthesis methods. This chapter focuses on the combination of tertiary amine Lewis base and transition metal catalysts, which the authors hope will simulate further developments and advances.

A Regio- and Stereodivergent Synthesis of Homoallylic Amines by a One-Pot Cooperative-Catalysis-Based Allylic Alkylation/Hofmann Rearrangement Strategy

Herein, we report a modular synthetic route to linear and branched homoallylic amines that operates through a sequential one-pot Lewis base/transition-metal catalyzed allylic alkylation/Hofmann rearrangement strategy. This protocol is operationally trivial, proceeds from simple and easily prepared substrates and catalysts, and enables all aspects of regio- and stereoselectivity to be controlled through a conserved experimental protocol. Overall, the high levels of enantio-, regio-, and diastereoselectivity obtained, in concert with the ability to access orthogonally protected or free amines, render this a straightforward and effective approach for the preparation of useful enantioenriched homoallylic amines. We have also demonstrated the utility of the products in the context of pharmaceutical synthesis.

A Modular Construction of Epidithiodiketopiperazines

Epidithiodiketopiperazines (ETPs) possess remarkably diverse biological activities and have attracted significant synthetic attention. The preparation of analogues is actively pursued; however, they are structurally challenging, and more direct and modular methods for their synthesis are desirable. To this end, the utility of a bifunctional triketopiperazine building block for the straightforward synthesis of ETPs is reported. A modular strategy consisting of enolate alkylation followed by site-selective nucleophile addition enables the concise synthesis of (±)-hyalodendrin and a range of analogues.

Passive transfer of allergic encephalomyelitis in rats: a tool for drug mechanism studies and detecting late-acting immunosuppressants

1. A strategy is described for evaluating drugs against different phases in the development of an auto allergic disease, experimental allergic encephalomyelitis. It is based on a cell transfer technique whereby the disease is passively transferred with lymphoid cells from actively immunized donor rats to normal syngeneic rats = passive recipients. Drugs may be applied in vivo to either the cell donors or the cell recipients or to cells in vitro whilst in transit; their efficiency being determined by the severity of the passive disease (weight loss, paralysis) in the recipients. 2. Examples are given illustrating the application of these techniques to: (a) evaluating the lymphocyte-deactivating activity of various nitrogen mustards in vitro; (b) recognizing drugs, e.g. gold derivatives, clofazimine, etc. that are not conventional immunosuppressant (or cytostatic) agents which, when given to the recipient animals, may prevent the expression of the adopted disease; (c) comparing some known immunosuppressants for potency, duration of action, etc.; (d) demonstrating the versatility of cycloleucine, ICI-47,776, etc. 3. Some merits of the strategy are discussed vis a vis using the local graft-versus-host reaction in rats to search for new drugs.

Traversing Steric Limitations by Cooperative Lewis Base/Palladium Catalysis: An Enantioselective Synthesis of α-Branched Esters Using 2-Substituted Allyl Electrophiles

Cooperative catalysis enables the direct enantioselective α-allylation of linear prochiral esters with 2-substituted allyl electrophiles. Critical to the successful development of the method was the recognition that metal-centered reactivity and the source of enantiocontrol are independent. This feature is unique to simultaneous catalysis events and permits logical tuning of the supporting ligands without compromising enantioselectivity.

Si-Directed regiocontrol in asymmetric Pd-catalyzed allylic alkylations using C1-ammonium enolate nucleophiles

Cooperative catalysis enables the direct enantioselective α-allylation of linear prochiral esters using Si-substituted allyl electrophiles. The Si-substituent directs the regioselectivity of enantioselective bond formation and provides products containing synthetically versatile pentafluorophenyl ester and vinylsilane moieties. Critical to the efficacy of this process was the recognition that the ancillary ligand on palladium could be altered to prevent formation of a deleterious ether by-product, whilst retaining enantioselectivity through the Lewis base catalyst. Flexibility such as this is unique to cooperative catalysis events and provides efficient access to an array of enantioenriched products that are orthogonally functionalized and easily modified.

Callipeltosides A, B and C: Total Syntheses and Structural Confirmation

Since their isolation almost 20 years ago, the callipeltosides have been of long standing interest to the synthetic community owing to their unique structural features and inherent biological activity. Herein we present our full research effort that has led to the synthesis of these molecules. Key aspects of our final strategy include 1) synthesis of the C1-C9 pyran core (5) using an AuCl3 -catalysed cyclisation; 2) formation of C10-C22 vinyl iodide (55) by sequential bidirectional Stille reactions and 3) diastereoselective union of these advanced fragments by means of an alkenylzinc addition (d.r.=91:9 at C9). The common callipeltoside aglycon (4) was completed in a further five steps. Following this, all three sugar fragments were appended to provide the entire callipeltoside family. In addition to this, D-configured callipeltose B was synthesised and appended to the callipeltoside aglycon. The (1) H NMR spectrum of this molecule was found to be significantly different to the natural isolate, further supporting our assignment of callipeltoside B (2).

Accelerating spirocyclic polyketide synthesis using flow chemistry

Over the past decade, the integration of synthetic chemistry with flow processing has resulted in a powerful platform for molecular assembly that is making an impact throughout the chemical community. Herein, we demonstrate the extension of these tools to encompass complex natural product synthesis. We have developed a number of novel flow-through processes for reactions commonly encountered in natural product synthesis programs to achieve the first total synthesis of spirodienal A and the preparation of spirangien A methyl ester. Highlights of the synthetic route include an iridium-catalyzed hydrogenation, iterative Roush crotylations, gold-catalyzed spiroketalization and a late-stage cis-selective reduction.

Highly efficient methods for the one-pot synthesis of β-substituted enones

A mild and practically-convenient one-pot procedure for the direct beta-substitution of enones has been developed using a conjugate addition-oxidation strategy with a full range of copper-based reagents and N-tert-butylphenylsulfinimidoyl chloride; alkyl- and aryl-substituted enones are delivered in good to excellent yields.

New odourless protocols for efficient Pauson–Khand annulations

An inexpensive and commercially available odourless additive, dodecyl methyl sulfide, has been shown to be a highly effective promoter in the Pauson-Khand cyclisation of both intra- and intermolecular substrates, affording good to excellent yields of cyclopentenone products.

Stroke Belt initiative: the Tennessee experience

African Americans have a higher rate of stroke than other U.S. population groups. As part of the 11-state "Stroke Belt" region, Tennessee has the fifth highest death rate from stroke in the country. In 1993, a two-year community-based project was initiated to reduce the incidence of stroke and its associated risk factors among African Americans. Three counties, Shelby (Memphis), Davidson (Nashville), and Hamilton (Chattanooga), were selected as project sites because of their large African American populations. Specific objectives of the project were to promote risk factor awareness in African Americans, assist African American churches and community groups in developing and implementing intervention programs, and build the capacity for intervention programs within African American communities by collaborating with a variety of community organizations. This article describes the program's approach, which included using both adults and youth as mentors. In addition, it presents major accomplishments and lessons learned in project implementation.

Preferential looking in clinical practice: a year's experience

Preferential Looking (PL) is now a well established laboratory method of measuring visual acuity in preverbal children. We have evaluated the feasibility of its routine use in clinical practice. We present our methods and results obtained in 80 normal children and 36 children with visual disorder and discuss the problems encountered in applying this test.

Analysis of transcripts homologous to acyl-CoA oxidase and enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase induced in rat liver by methylclofenapate

Methylclofenapate is a potent peroxisome proliferating agent and liver carcinogen in rats. Animals exposed to daily oral doses (2.5 mg/kg body wt.) for a 21-day period were studied to determine the levels of mRNA homologous to peroxisomal acyl-CoA oxidase and enoyl-CoA hydratase/3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme in total liver RNA. Northern blotting revealed transcripts of approximately 3.8 and 3.3 kilobases (kb), homologous to acyl-CoA oxidase and the bifunctional enzyme, respectively. Levels of these transcripts began to rise at approximately 4 h after the initial dose of the agent, and reached maximum induction (35- and 60-fold, respectively, in excess of control levels) at 2-8 days after the start of the study. The kinetics of induction for acyl-CoA oxidase mRNA resembled those of palmitoyl-CoA oxidase activity, and the induction of mRNA preceded the expression of enzyme activity, further supporting a transcriptional control model of induction of the peroxisomal enzymes. The levels of mRNA induction for the peroxisomal enzymes were higher in the present study than those reported elsewhere for single doses of peroxisome proliferating agents and probably reflect the increased tissue levels achievable in long term carcinogenesis studies.

Regulation of cell shape in the Cloudman melanoma cell line

We show that Cloudman melanoma cells undergo rapid arborization in response to [Nle4,D-Phe7]alpha-melanocyte-stimulating hormone, a potent analogue of alpha-melanocyte stimulating hormone (alpha-MSH). The arbors were established by extension of processes and resembled dendrites. We used this system to study the regulation of cell shape. alpha-MSH is known to induce increases in cAMP levels, and agents such as forskolin and isobutylmethylxanthine that led to increased cAMP also caused arborization. However, equally dramatic arbors were formed after incubation with the protein kinase C inhibitor H-7 [1-(5-isoquinolinesulfonyl)-alpha-methyl-piperazine]. Phorbol diesters that activate protein kinase C led to cell rounding and antagonized alpha-MSH. The actions of protein kinase C cannot be rationalized in terms of indirect effects on cAMP: neither H-7 nor phorbol diesters alone altered cAMP levels, nor did they affect the increase in cAMP induced by MSH. We show also that MSH produced longer-term effects that cannot be mimicked by cAMP. Specifically, even in the continued presence of alpha-MSH, arborization was followed by morphological reversal to the unstimulated flattened configuration within 2 hr. (This did not occur with other agents that increase cAMP or with H-7.) Most importantly, whereas MSH-induced arborization occurred in the presence of cycloheximide, actinomycin D, or in enucleated cells, the reversal of arborization did not. Thus, MSH induced a program of rapid shape change that was dependent on new protein synthesis and gene transcription.

Resistance of mouse lymphoma L5178YAII cells to alkylation with methylmethane sulphonate resides in a late step of excision repair

The mutant mouse lymphoma cell line (L5178YAII), resistant to X-rays, ultraviolet light and alkylating agents, was reinvestigated in an attempt to establish the nature of the mutation. These cells were compared with P388 mouse lymphoma cells, which exhibit normal sensitivity to these mutagens. A series of studies was conducted to compare DNA alkylation and strand breakage with cell survival after exposure of the two cell lines to methylmethane sulphonate. It was found that neither the degree of alkylation nor the removal of the common alkylation products was correlated with the different sensitivities observed in these cell lines. A correlation was established between cell killing and the production of long-lived strand breaks. P388 cells were found to accumulate twice as many long-lived strand breaks compared to L5178YAII cells, at equal levels of alkylation. This suggested that long-lived strand breaks were the major toxic lesions. Further experiments indicated that these long-lived strand breaks were produced by a process consistent with excision repair. Evidence is also presented that indicates that the mutation in L5178YAII cells that is responsible for their resistance may occur in ligase activity or its associated ADP-ribosyl transferase system.

Effects of hydroxyurea consistent with the inhibition of repair synthesis in ultraviolet irradiated HeLa cells

Many studies on DNA repair using established in vitro cell cultures employ conditions of low serum, nutrient deprivation, and blockade with hydroxyurea (HU) to reduce the background levels of DNA replication. There are some reports in the literature which indicate that HU inhibits DNA repair. In the present study the effects of HU on strand breaks and repair synthesis in UV irradiated Hela cells were investigated using a combined strand break and UDS assay. In conditions of low serum and arginine deprivation, HU produced effects consistent with the inhibition of the repair synthesis step in excision repair. Although the conditions used in this study are severe the results suggest that HU may have qualitatively similar effects in other studies which employ its use to detect repair synthesis.

An investigation of DNA-repair phenomena induced by 4-chloromethylbiphenyl (4CMB)

The ability of 4CMB to induce repair phenomena has been investigated in 3 types of assay. No significant unscheduled DNA synthesis or repair replication was found, although the compound gave a weakly positive dose-related response in strand-break assays, with 250 microgram/ml producing significant amounts of strand breaks. These data indicate that 4CMB is a weakly genotoxic agent.

Muscle adenylate deaminase deficiency. Report of six new cases

We describe six adult patients (five men and one woman) out of 364 whose muscle biopsy specimens disclosed muscle adenylate deaminase deficiency. Two men had an associated dermatomyositis and another man had an associated progressive systemic sclerosis. Although the patients were different clinically, all complained of muscular weakness or poor exercise tolerance. The occurrence of muscle adenylate deaminase deficiency in both sexes suggests a possible autosomal mode of inheritance.

Adjuvant polyarthritis. V. Induction by N-acetylmuramyl-L-alanyl-D-isoglutamine, the smallest peptide subunit of bacterial peptidoglycan

N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP), an apparently nonimmunogenic bacterial peptidoglycan-derived small peptide, was found to induce a polyarthritis the rat similar to that induced by Freund's complete adjuvant when injected in the form of an oil emulsion. An oil emulsion of its isomer, N-acetylmuramyl-L-alanyl-L-isoglutamine, which unlike MDP has no immunostimulatory activity, failed to induce the disease.

Adenylosuccinase in human muscular dystrophy

The level of adenylosuccinase was measured in muscle from patients with Duchenne and other major forms of progressive muscular dystrophies and certain related neuromuscular diseases. The activity was found to be unaltered in all diseases that were examined.

Role of thymus for N-acetyl muramyl-L-alanyl-D-isoglutamine-induced polyarthritis and granuloma formation in euthymic and athymic nude rats or in neonatally thymectomized rats

A synthetic adjuvant, N-acetyl muramyl-L-alanyl-D-isoglutamine (MDP), produced extremely severe polyarthritis with almost 100% incidence in Rowett euthymic rnu/+ rats, but the same dose of MDP (100 microgram) did not produce the disease in athymic rnu/rnu rats. Five hundred micrograms of MDP or 0.2 mg of heat-killed Mycobacterium bovis BCG, however, produced mild and transient polyarthritis in nude rats with very low incidence. We have not yet succeeded in reconstituting the disease susceptibility of nude rats by using thymus cells from normal rnu/+ rats. After intradermal inoculation of 100 microgram of MDP, nude rats developed small granulomas with a little necrosis and very few multinucleated giant cells only in the regional lymph nodes, whereas, in addition to the development of polyarthritis, euthymic rnu/+ rats developed typical granuloma with massive necrosis accompanied by numerous polymorphonuclear leukocytes and sparse multinucleated giant cells in the regional lymph nodes. Thymus cell-reconstituted rnu/rnu rats developed granuloma with sparse giant cells, relatively large areas of necrosis, and many polymorphonuclear leukocytes. Neonatal thymectomy may depress adjuvant-induced arthritis in the high-responder Lewis rats and enhance the disease development in the low-responder F344 rats. These findings suggested that (i) thymus plays an important role in promoting the development of MDP-induced arthritis; (ii) MDP-induced granuloma formation does not require thymus functions; (iii) the thymus functions may however be involved in the development of massive necrosis surrounded by considerable polymorphonuclear leukocyte infiltration, the mechanisms of which remain to be determined; and (iv) there is no direct correlation between granuloma formation and development of adjuvant arthritis.

Methylthioadenosine nucleosidase in normal and dystrophic human muscle

Human skeletal muscle homogenate was found to contain a nucleosidase that catalyzes the hydrolysis of 5'-methylthioadenosine, a known inhibitor of many methyl transfer reactions. When the levels of methylthioadenosine nucleosidase in muscle of patients were compared with those of controls, no significant alterations in its activity were noted in patients with various forms of muscular dystrophies, polymyositis and certain denervating diseases.

Muscle fructose 1,6-diphosphatase deficiency associated with an atypical central core disease

A 25-year-old woman with a non-familial congenital nonprogressive myopathy was found to have atypical core-like lesions in type 1 muscle fibers. Typical core lesions (approximately 13 micrometers in diameter) and smaller, PAS positive (4.1 micrometers in diameter) atypical core were associated with a predominant type 1 fibre myopathy. A specific deficiency of fructose 1, 6-diphosphatase was found with normal values for nine other muscle glycolytic and mitochondrial marker enzymes. The data provide evidence for a specific muscle enzyme deficiency in a patient with atypical central core disease.

Adjuvant polyarthritis. IV. Induction by a synthetic adjuvant: immunologic, histopathologic, and other studies

A solution of an apparently nonimmunogenic synthetic compound, N,N-dioctadecyl-N',N'-bis(2-hydroxyethyl) propanediamine (CP-20961), suspended in mineral oil or olive oil (50 mg/ml), induced an acute, as well as a chronic, polyarthritis when single intradermal injections (0.2 ml) were made in the tail or hindpaw of Lewis rats. The polyarthritis was morphologically almost indistinguishable from classic adjuvant arthritis induced by Freund's complete adjuvant (FCA), a disease generally thought to be the result of a delayed hypersensitivity reaction to a constituent(s) of the injected tubercle bacilli. The disease induced by CP-20961 and that induced by Freund's complete adjuvant followed the same time course and almost identical pattern of development of clinical and histopathologic features. Like the classic adjuvant arthritis, CP-20961 induced arthritis is suppressed by an immunosuppressive agent (cyclophosphamide) or an antiinflammatory drug (phenylbutazone). The alkyldiamine (CP-20961) was found to be a potent adjuvant; a dispersion or a solution of the compound in mineral oil administered intraperitoneally enhanced the development of both the cell-mediated and the humoral immune responses to EL4 cells in the rat. These findings suggest that the immunogen responsible for the development of adjuvant arthritis is endogensou, e.g., a constituent of host tissue, a viral protein, or some complex of the two.

Catalase, superoxide dismutase, glutathione reductase and thiobarbituric acid-reactive products in normal and dystrophic human muscle

The level of thiobarbituric acid-reactive products and the specific activities of catalase and glutathione reductase were significantly higher in muscles from patients with major forms of muscular dystrophies over those of control subjects. Superoxide dismutase activity was not altered in dystrophic muscles. These findings indicate the occurrence in human dystrophic muscles of an increased level of lipid peroxidation and the possible activation of certain enzymes that could conceivably inhibit lipid peroxidation in vivo.

Activity of some proteolytic enzymes in normal and dystrophic human muscle

1. The following proteolytic enzymes were measured in muscles of control subjects and patients with muscular dystrophies and related neuromuscular diseases: an elastase-like enzyme, carboxypeptidase A, carboxypeptidase B and pyroglutamyl peptidase. 2. Elastase-like enzyme and carboxypeptidase B did not show significant alterations in various disease conditions that were examined. 3. Carboxypeptidase A was moderately elevated in dystrophic as well as other diseased muscles. 4. Pyroglutamyl peptidase was not markedly altered in any disease condition except that is was slightly lower in dystrophic muscles.

Muscle breakdown and lysosomal activation (biochemistry)

Muscle tissue levels of lysosomal catheptic enzymes, such as cathepsins D, A, B1, C, and dipeptidyl peptidase II, were measured in control subjects and patients with muscular dystrophies, polymyositis, and certain denervating diseases. The results show that, in general, the activities of these enzymes are increased in muscles of patients with muscular dystrophies and other diseases. The increases in cathepsin D and autolytic activities are not significant until the late stage of the disease process. Cathepsins A, B1, and C are, however, significantly elevated in mildly affected dystrophic and other diseased muscles. Of these catheptic enzymes, cathepsin B1 displays the highest rise at an early stage, suggesting that it may be one of the rate-controlling enzymes of proteolysis. Dipeptidyl peptidase II is increased slightly in dystrophic and other myopathic muscles but is unchanged in denervated muscle. These data clearly implicate the lysosomal group of proteinases as largely responsible for mediating muscle breakdown in the muscular dystrophies and certain other muscle and neuromuscular diseases in man.

Workshop IV. Aetiopathogenetic factors in Reiter's syndrome. Adjuvant disease: pathology and immune reactivity

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Muscular dystrophy and activation of proteinases

Evidence is presented for the existence of many different systems of proteolytic enzymes in human skeletal muscle. These include the lysosomal system of cathepsins as well as proteinases and peptide hydrolases that are optimally active at neutral and alkaline pH ranges. The majority of proteolytic enzymes examined are found to show increased activity in dystrophic human muscle. Moreover, a high initial rise is observed in cathepsin B1, a thiol-dependent endopeptidase of lysosomes, and in dipeptidyl peptidase IV, a membrane-associated peptidase. In addition, a calcium-activated neutral proteinase is found to be significantly elevated in muscle from patients with Duchenne dystrophy. The possible roles of these proteinases in intracellular protein catabolism and muscle wasting are discussed.