MCR III1. Multicomponent Reactions and Their Libraries,a New Type of Organic Chemistry of the Isocyanides and Phosphorus Derivatives.

Abstract

Various new one-pot multicomponent reactions (MCRs) of C^II and P^III derivatives and their libraries are described here. The preparation of some nucleobase- and phospholipid compound libraries by MCRs have been carried out.

     

Recent advances in isocyanide-based multicomponent chemistry

Multicomponent reactions (MCRs) provide a powerful tool towards the one-pot synthesis of diverse and complex compounds on the one hand and small and 'drug-like' heterocycles on the other hand. No other single synthesis technology enables chemists to search such large chemical spaces as provided by MCRs. MCRs that involve isocyanides are by far the most versatile reactions in terms of scaffolds and number of accessible compounds.     

The crystal structure of AbsH3: A putative flavin adenine dinucleotide‐dependent reductase in the abyssomicin biosynthesis pathway

Natural products and natural product‐derived compounds have been widely used for pharmaceuticals for many years, and the search for new natural products that may have interesting activity is ongoing. Abyssomicins are natural product molecules that have antibiotic activity via inhibition of the folate synthesis pathway in microbiota. These compounds also appear to undergo a required [4 + 2] cycloaddition in their biosynthetic pathway. Here we report the structure of an flavin adenine dinucleotide‐dependent reductase, AbsH3, from the biosynthetic gene cluster of novel abyssomicins found in Streptomyces sp. LC‐6‐2.     

组合生物催化

自然界最有效的分子是由酶催化的反应所产生,并对这些产物进行自然选择,使其具有优化的生理活性,组合生物催化（Combinatorial Biocatalysis)利用酶反应的多样性,完成有机库（Organic Library)的反复合成,这些反复的反应,可以用分离的酶或全细胞,在天然或非天然的环境中、在溶液或固相中与底物进行反应。组合生物催化是组合方法的在药物发现和发展中产生和优化先导化合物（LeadCompound)的一个有力补充。     

Exploring the physicochemical and antiproliferative properties of biaryl-linked [13]-macrodilactones

A macrocyclic motif fosters productive protein-small molecule interactions. There are numerous examples of both natural product and designed, synthetic macrocycles that modulate the immune system, slow microbial infection, or kill eukaryotic cells. Reported here are the synthesis, physicochemical characterization, and antiproliferative activity of a group of [13]-macrodilactones decorated with a pendant biaryl moiety. Biaryl analogs were prepared by Suzuki reactions conducted on a common intermediate that contained a bromophenyl unit alpha to one of the carbonyls of the [13]-macrodilactone. Principal component analysis placed the new compounds in physicochemical context relative to a variety of pharmaceuticals and natural products. Modest inhibition of proliferation was observed in ASZ cells, a murine basal cell carcinoma line. This work underscores the value of an approach toward the identification of bioactive compounds that places the evaluation of physicochemical parameters early in the search process.     

Current developments and challenges in the search for a naturally selected Diels-Alderase

Only a very few examples of enzymes known to catalyze pericyclic reactions have been reported, and presently no enzyme has been demonstrated unequivocally to catalyze a Diels-Alder reaction. Nevertheless, research into secondary metabolism has led to the discovery of numerous natural products exhibiting the structural hallmarks of [4+2] cycloadditions, prompting efforts to characterize the responsible enzymatic processes. These efforts have resulted in a growing collection of enzymes believed to catalyze pericyclic [4+2] cycloaddition reactions; however, in each case the complexity of the substrates and catalytic properties of these enzymes poses significant challenges in substantiating these hypotheses. Herein we consider the principles motivating these efforts and the enzymological systems currently under investigation.     

Natural product-like libraries based on non-aromatic, polycyclic motifs

Diversity-oriented synthesis is an intriguing approach for creating structurally diverse compounds that cover the pharmaceutically relevant chemical space in an optimal way. On the other hand, an over-proportionally large number of drugs or lead structures originate from compounds isolated from natural sources. Thus, not surprisingly, an increasing number of combinatorial libraries are based on motifs resembling natural products. A particular aspect of many natural products is the presence of non-aromatic, polycyclic core structures. The fusion of several rings leads to geometrically well-defined structures and, thus, holds the promise of a high functional specialisation. In this review we present several actual examples of natural product-like libraries with non-aromatic polycyclic motifs based on naturally occurring compounds.     

Studies of oligoadenylate formation on a poly(U) template

We have studied a variety of condensation reactions involving poly (U) as template and isomeric adenosine dinucleotides as substrates. We find that [3'-5']-linked dinucleotides such as A3pA and pA3pA are better acceptors than the corresponding [2'-5']-linked compounds, while ImpA2pA is a better donor than ImpA3pA. The reaction between A2pA and ImpA3pA, for example, yields only 4% of product while the reaction of A3pA with ImpA2pA yields 86% of product. The more efficient condensation reactions of dimers are about as efficient as the self-condensation of ImpA. They yield a few percent of material in which five or more substrate molecules are linked together. The percentage of the natural [3'-5']-linkage in the product varies greatly, from as little as 1% to as much as 45%.     

ESI-MS studies on novel liquid homo-peptide libraries and their conjugate libraries directed by phosphorus oxychloride

Summary The reactions of natural non-polar amino acids with phosphorus oxychloride were investigated. Some non-polar amino acids, such as L-Phe, L-Leu and L-Val were treated with phosphorus oxychloride, then quenched with water or some bioactive compounds (L-menthol, cinchonidine and benzylamine), and yielded the corresponding peptide and peptide conjugate libraries. ESI-MS/MS was used to study the products of the reaction and confirm the structure of the library. This paper reports a simple method to synthesize the homo-oligo-peptide libraries and peptide conjugated libraries.     

多组分反应在吡咯衍生物合成中的应用进展

多组分反应(Multicomponent Coupling Reactions,MCRs)是将三种或三种以上的相对简单的原料加入"一锅煮"反应中,不经过中间体分离而直接得到结构复杂的分子的方法。具有操作简单、原料易得、环境友好等优点。多组分反应发展至今,已经在包括药物合成的多个领域中起到了重要作用。吡咯衍生物作为一类在自然界中广泛分布、有着重要生物医药价值和材料科学价值的重要化合物,其合成方法一直是有机合成研究中的热点之一。近年来用于合成吡咯衍生物的多组分反应也不断地被报道。多组分反应能够很好地解决传统吡咯合成路线中取代基引入的问题并能提高反应收率,为吡咯衍生物的合成与研究带来便利。本文从合成方法上概述了近年来多组分反应在吡咯合成中的应用,为合成已有吡咯衍生物和探寻全新结构的吡咯衍生物提供合成方法上的新思路。     

Kinetic co-operativity of wheat-germ RNA polymerase II with adenosine 5''-[beta gamma-imido]triphosphate as substrate.

A kinetic study of productive RNA chain elongation indicates that adenosine 5'-[beta gamma-imido]triphosphate can serve as substrate in reactions catalysed by purified wheat-germ RNA polymerase II on a poly[d(A-T)] template. However, in contrast with the results obtained with the natural substrate ATP, the double-reciprocal plots, 1/velocity versus 1/[nucleotide], are not linear but characteristic of apparent negative co-operativity. The extent of the kinetic co-operativity is modified when the reactions are conducted in the additional presence of fixed amounts of an alternative substrate such as ATP or inhibitors such as dATP or cordycepin triphosphate. Analogous results are obtained whether the reactions are carried out in the presence of Mg2+ or Mn2+ as the metal ion cofactor. However, the data show that with Mn2+ the RNA polymerase is less specific in substrate recognition than with Mg2+. Tentative kinetic models are proposed to account for the rate measurements.     

Strategies towards potent trypanocidal drugs: Application of Rh-catalyzed [2 + 2 + 2] cycloadditions,sulfonyl phthalide annulation and nitroalkene reactions for the synthesis of substituted quinones and their evaluation against Trypanosoma cruzi

Rhodium-catalyzed [2 + 2 + 2] cycloadditions, sulfonyl phthalide annulations and nitroalkene reactions have been employed for the synthesis of 56 quinone-based compounds. These were evaluated against Trypanosoma cruzi, the parasite that causes Chagas disease. The reactions described here are part of a program that aims to utilize modern, versatile and efficient synthetic methods for the one or two step preparation of trypanocidal compounds. We have identified 9 compounds with potent activity against the parasite; 3 of these were 30-fold more potent than benznidazole (Bz), a drug used for the treatment of Chagas disease. This article provides a comprehensive outline of reactions involving over 120 compounds aimed at the discovery of new quinone-based frameworks with activity against T. cruzi.     

Mineralization of sulfonated azo dyes and sulfanilic acid by Phanerochaete chrysosporium and Streptomyces chromofuscus.

Five 14C-radiolabeled azo dyes and sulfanilic acid were synthesized and used to examine the relationship between dye substitution patterns and biodegradability (mineralization to CO2) by a white-rot fungus and an actinomycete. 4-Amino-[U-14C]benzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-[U-14C]benzenesulfonic acid were used as representative compounds having sulfo groups or both sulfo and azo groups. Such compounds are not known to be present in the biosphere as natural products. The introduction of lignin-like fragments into the molecules of 4-amino-[U-14C]benzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-[U-14C]benzenesulfonic acid by coupling reactions with guaiacol (2-methoxyphenol) resulted in the formation of the dyes 4-(3-methoxy-4-hydroxyphenylazo)-[U-14C]benzenesulfonic acid and 4-(2-sulfo-3'-methoxy-4'-hydroxy-azobenzene-4-azo)-[U-14C]benzenesulf oni c acid, respectively. The synthesis of acid azo dyes 4-(2-hydroxy-1-naphthylazo)-[U-14C]benzenesulfonic acid and 4-(4-hydroxy-1-naphthylazo)-[U-14C]benzenesulfonic acid also allowed the abilities of these microorganisms to mineralize these commercially important compounds to be evaluated. Phanerochaete chrysosporium mineralized all of the sulfonated azo dyes, and the substitution pattern did not significantly influence the susceptibility of the dyes to degradation. In contrast, Streptomyces chromofuscus was unable to mineralize aromatics with sulfo groups and both sulfo and azo groups. However, it mediated the mineralization of modified dyes containing lignin-like substitution patterns. This work showed that lignocellulolytic fungi and bacteria can be used for the biodegradation of anionic azo dyes, which thus far have been considered among the xenobiotic compounds most resistant to biodegradation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Mineralization of sulfonated azo dyes and sulfanilic acid by Phanerochaete chrysosporium and Streptomyces chromofuscus.

Five 14C-radiolabeled azo dyes and sulfanilic acid were synthesized and used to examine the relationship between dye substitution patterns and biodegradability (mineralization to CO2) by a white-rot fungus and an actinomycete. 4-Amino-[U-14C]benzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-[U-14C]benzenesulfonic acid were used as representative compounds having sulfo groups or both sulfo and azo groups. Such compounds are not known to be present in the biosphere as natural products. The introduction of lignin-like fragments into the molecules of 4-amino-[U-14C]benzenesulfonic acid and 4-(3-sulfo-4-aminophenylazo)-[U-14C]benzenesulfonic acid by coupling reactions with guaiacol (2-methoxyphenol) resulted in the formation of the dyes 4-(3-methoxy-4-hydroxyphenylazo)-[U-14C]benzenesulfonic acid and 4-(2-sulfo-3'-methoxy-4'-hydroxy-azobenzene-4-azo)-[U-14C]benzenesulf oni c acid, respectively. The synthesis of acid azo dyes 4-(2-hydroxy-1-naphthylazo)-[U-14C]benzenesulfonic acid and 4-(4-hydroxy-1-naphthylazo)-[U-14C]benzenesulfonic acid also allowed the abilities of these microorganisms to mineralize these commercially important compounds to be evaluated. Phanerochaete chrysosporium mineralized all of the sulfonated azo dyes, and the substitution pattern did not significantly influence the susceptibility of the dyes to degradation. In contrast, Streptomyces chromofuscus was unable to mineralize aromatics with sulfo groups and both sulfo and azo groups. However, it mediated the mineralization of modified dyes containing lignin-like substitution patterns. This work showed that lignocellulolytic fungi and bacteria can be used for the biodegradation of anionic azo dyes, which thus far have been considered among the xenobiotic compounds most resistant to biodegradation.(ABSTRACT TRUNCATED AT 250 WORDS)     

Insecticidal lead identification by screening benzopyrano[4,3-c] pyrazol-3(2H)-ones library constructed from multiple-parallel synthesis under microwave irradiation

A rapid library-generation via liquid-phase multiple-parallel synthesis of 2-(substituted)benzyl-1-benzopyrano[4,3-c]pyrazol-3(2H)-ones, bearing two points of diversity, under microwave irradiation was successfully performed using chromenone-3-carboxylic acids as starting materials. Compared to an identical library generated by conventional parallel synthesis, microwave-assisted parallel synthesis dramatically decreased reaction times from an average of 16 h to 13 min, and the yields of products and intermediates were improved in most cases. A bioassay indicated that the compounds of the library exhibited excellent insecticidal activity against T. cinnabarinus at the dosage of 250 mg L⁻¹, and some compounds still exhibited insecticidal activity when the dosage was reduced to 50 mg L⁻¹. This shows that 2-(substituted) benzyl-1-benzopyrano[4,3-c]pyrazol-3(2H)-ones might be used as lead structures for further optimization. To our knowledge, this is the first report about the application of solution-phase multiple-parallel synthesis under microwave irradiation to construct libraries of benzopyrano-[4,3-c]pyrazol-3(2H)-ones with insecticidal activity. The coupling of microwave technology with liquid-phase parallel synthesis constitutes a novel and particularly attractive avenue for the rapid generation of structurally diverse libraries for lead discovery.     

Carbon-13 nuclear magnetic resonance analysis of [1-13C]glucose metabolism in Crithidia fasciculata. Evidence of CO2 fixation by phosphoenolpyruvate carboxykinase

The non-invasive technique of 13C nuclear magnetic resonance was applied to study glucose metabolism in vivo in the insect parasite Crithidia fasciculata. It was found that under anaerobic conditions [1-13C]glucose underwent a glycolytic pathway whose main metabolic products were identified as [2-13C]ethanol, [2-13C]succinate and [1,3-13C2]glycerol. These metabolites were excreted by C. fasciculata into the incubation medium, while in the cells [3-13C]phosphoenolpyruvate was also detected in addition to the aforementioned compounds. The C3 acid is apparently the acceptor of the primary CO2 fixation reaction, which leads in Trypanosomatids to the synthesis of succinate. By addition of sodium bicarbonate to the incubation mixture L-[3-13C]malate was detected among the excretion products, while the ethanol:succinate ratio of 2.0 in the absence of bicarbonate changed to a ratio of 0.6 in the presence of the latter. This was due to a shift of the balance between carboxylation of phosphoenolpyruvate, leading to succinate, and pyruvate decarboxylation leading to ethanol. The addition of 25% 2H2O to the incubation mixture led to the formation of [2-13C, 2-2H]ethanol derived from the prior incorporation of 2H+ into pyruvate in the reactions mediated by either pyruvate kinase or malic enzyme. However, no 2H+ incorporation into L-malate was detected, excluding the possibility that the latter was formed by carboxylation of pyruvate, and lending support to the idea that L-malate results from the carboxylation of phosphoenolpyruvate to oxaloacetate by phosphoenolpyruvate carboxykinase. The formation of [2-13C, 2-2H]-succinate under the same conditions reflected the uptake of 2H+ during the reduction of fumarate. When the incubations were carried out in the presence of 100% 2H2O, several [1-13C, 1-2H]ethanol species were detected, as well as [2-13C, 2-2H]malate and [1,3-13C2, 1,3-2H2]glycerol. The former deuterated compounds reflect the existence of NAD2H species when the incubations were carried out in 100% 2H2O, while the incorporation of 2H+ into [1,3-13C2]glycerol must be attributed to the phosphoglucose-isomerase-mediated reaction during glycolysis.     

海洋链霉菌Streptomyces sp. B9173合成的2-吲哚酮生物碱

【背景】海洋来源的天然产物近年来已成为小分子药物的重要来源。对海洋链霉菌Streptomyces sp. B9173的基因组分析显示,该菌包含多种天然产物的生物合成基因簇,具有产生多种新化合物的潜力。【目的】挖掘B9173菌株中未知的次级代谢产物,以期发现结构新颖或生物活性独特的化合物。【方法】利用HPLC/LC-MS结合的方法,排除了该菌株产生的已知化合物,确定3个未知化合物作为挖掘对象,然后利用正、反相硅胶柱色谱、葡聚糖凝胶柱色谱和高效液相色谱等技术对次级代谢产物进行分离纯化,最后得到化合物单体。利用质谱及核磁共振光谱技术对化合物结构进行解析和鉴定。【结果】确定3个化合物分别是色胺酮、甲基异靛蓝和N,N-二甲基异靛蓝,三者都属于2-吲哚酮生物碱。其中色胺酮具有非常广的生物活性,包括抗菌、抗肿瘤、抗炎症等,是药物开发的良好前体,这是首次在细菌中被分离得到。甲基异靛蓝是我国临床治疗慢性粒细胞白血病的药物,这是首次在微生物发酵液中被分离得到。目前这3个化合物均主要依赖化学合成。本研究结合B9173菌株的代谢背景,推测了3个化合物的生物合成途径。【结论】基于紫外吸收光谱和质谱特征,从B9173菌株的发酵液中分离鉴定了3个2-吲哚酮生物碱,丰富了微生物活性天然产物的种类,对3个化合物生物合成途径的推测也为进一步研究色胺酮和甲基异靛蓝的生物合成机制奠定基础,后续可利用合成生物学技术重构这类化合物的生物合成途径,提供更便捷、低成本的生物合成方法。     

Natural products as a screening resource

Natural products have been the most productive source of leads for new drugs, but they are currently out of fashion with the pharmaceutical industry. New approaches to sourcing novel compounds from untapped areas of biodiversity coupled with the technical advances in analytical techniques (such as microcoil NMR and linked LC-MS-NMR) have removed many of the difficulties in using natural products in screening campaigns. As the 'chemical space' occupied by natural products is both more varied and more drug-like than that of combinatorial chemical collections, synthetic and biosynthetic methods are being developed to produce screening libraries of natural product-like compounds. A renaissance of drug discovery inspired by natural products can be predicted.     

Structure-activity relationship and signal transduction of gamma-MSH peptides in GH3 cells: further evidence for a new melanocortin receptor

The structure-activity relationship and signal transduction properties of the pro-opiomelanocortin (POMC)-derived gamma-MSH peptides in the GH3 cell line was compared with that described for the known melanocortin receptors (MCRs). Single alanine replacements showed that, unlike the classical MCRs, the His(5)-Phe(6)-Arg(7)-Trp(8) sequence in gamma2-MSH is not a core sequence for activating the gamma-MSH receptor in GH3 cells, whereas Met(3) is essential. gamma2-MSH increased binding of [35S]GTPgammaS to membrane preparations of GH3 cells. Blockade of protein kinase A abolished the [Ca(2+)](i) responses to gamma3-MSH, and low nanomolar doses of gamma3-MSH increased intracellular cAMP levels, which could be blocked by pertussis toxin (PTX). We conclude that the putative novel gamma-MSH receptor in GH3 cells is a GPCR, but with structure-activity and signal transduction features different from those of the classical MCRs.     

海绵来源链霉菌S52-B中氨酰胺天然产物的分离与鉴定

【背景】海洋微生物是复杂海洋生态环境中重要的生物资源之一。海洋微生物所产生的活性天然产物极为丰富,是药物或药物先导化合物的重要来源。【目的】探索海洋中海绵来源链霉菌Streptomycessp.S52-B的优势生长条件,挖掘其次级代谢产物,以期分离具有良好生物活性的天然产物。【方法】根据"One Strain Many Compounds"(OSMAC)策略,寻找利于Streptomyces sp. S52-B生长和次级代谢产物产生的优势培养基,结合质谱及特征性的紫外吸收谱图,选择培养基进行大量发酵。利用正相硅胶柱色谱、葡聚糖凝胶柱色谱和制备型高效液相色谱等进行分离纯化,并应用高分辨质谱和核磁共振光谱进行化合物结构解析。【结果】确定培养基A–D为海洋链霉菌S52-B的优势培养基,基于紫外吸收光谱与质谱分析,从培养基A的大量发酵物中分离鉴定3个具有吡咯并[4,3,2-de]喹啉核心结构的含氯化合物,属于氨酰胺类天然产物,其中Ammosalic acid为新结构化合物。【结论】已知含有吡咯并喹啉母核的氨酰胺类家族化合物具有优良的抗癌活性。本研究从海绵来源链霉菌S52-B中分离鉴定了3个氨酰胺类化合物,其中一个是新结构化合物,不仅丰富了此类化合物家族的结构类型,也为研究其生物合成途径中的未知机理奠定了基础,还有利于结合培养条件和基因组信息从这株海绵来源链霉菌中挖掘新结构的活性天然产物。