Convergent assembly of highly potent analogues of bryostatin 1 via pyran annulation: bryostatin look-alikes that mimic phorbol ester function

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.     

Synthesis of a 4H-anthra[1,2-b]pyran derivative and its antimicrobial activity

The five-step synthesis of the new 4H-anthra[1,2-b]pyran derivative 1 is reported. The key steps in this approach included a Marschalk alkylation of 1,4-dihydroxyanthraquinone followed by a Baker-Venkataraman reaction and then an acid-catalyzed cyclization of ring A to form the 4H-anthra[1,2-b]pyran system. Two compounds, the 4H-anthra[1,2-b]pyran 1 and the anthraquinone derivative 6 were evaluated for antimicrobial activity and showed moderate antialgal, antifungal, and antibacterial activities.     

Synthesis of Novel Pyran β-Amino Acid and 5,6-Dihydro-2H-pyran β-aminoxy Acid from Carbohydrate Derivatives

Synthesis of two new amino acids, containing pyran rings, is reported from carbohydrate derivatives. The cis-3-amino-pyran-2-carboxylic acid (cis-APyC) was prepared from (R)-glyceraldehyde derivative, using nucleophilic substitution reaction for pyran ring formation. Similarly, the trans-3-aminoxy-5,6-dihydro-2H-pyran-2-carboxylic acid (trans-AmPyC) was prepared from diacetone glucose (DAG), using ring closing metathesis (RCM) reaction for the ring formation.     

A High Yielding Synthesis of Racemic Hongconin

Racemic hongconin 1 has been synthesized from adduct 2 formed by reaction between 1-methoxycyclohexa-1,4-diene and benzoquinone. The synthetic strategy includes Fries and Claisen rearrangements, base and cerium(IV) initiated pyran ring formation, C-4 pyran ring hydroxylation and silver(II) mediated oxidation.     

A new direction in the alkylation of 5‐acetyl‐2‐amino‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile with active methylene reagents

In this paper, we report a new synthesis route to 4H‐pyran derivatives and a plausible reaction mechanism. The interaction of 5‐acetyl‐2‐amino‐6‐methyl‐4‐phenyl‐4H‐pyran‐3‐carbonitrile with different active methylene reagents gives rise to the cleavage and subsequent recyclization of the pyran ring to afford the corresponding 4H‐pyran derivatives.     

Biotransformation of aristolane- and 2,3-secoaromadendrane-type sesquiterpenoids having a 1,1-dimethylcyclopropane ring by Chlorella fusca var. vacuolata, mucor species, and Aspergillus niger

Biotransformation of the aristolane-type sesquiterpene hydrocarbon (+)-1(10)-aristolene (1) from the crude drug Nardostachys chinensis and of the 2,3-secoaromadendrane-type sesquiterpene lactone plagiochilide (2) from the liverwort Plagiochila fruticosa by three microorganisms, Chlorella fusca var. vacuolata, Mucor species, and Aspergillus niger was investigated. C. fusca var. vacuolata and Mucor sp. introduced oxygen function into the cyclohexane ring of aristolene while A. niger oxidized stereoselectively one methyl of the 1,1-dimethyl group on the cyclopropane ring of aristolanes and 2,3-secoaromadendrane to give C-12 primary alcohol and C-12 carboxylic acid. The possible metabolic pathway of the formation of new metabolites is discussed. The stereostructures of new metabolites were established by a combination of NMR spectroscopy including HMBC and NOESY, X-ray crystallographic analysis, and chemical reaction.     

4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one: Synthesis and reactivity with amines

The synthesis and reactivity studies of 4‐hydroxy‐6‐methyl‐3‐(5‐phenyl‐2E,4E‐pentadien‐1‐oyl)‐2H‐pyran‐2‐one 2 with nucleophiles are reported. Reactions of 2 with hydrazine derivatives gave new pyrazole‐type com pounds while the reaction with ortho‐phenylenediamines yielded 1,5‐benzodiazepines. The reaction of 2 with ethylamine implies the 2H‐pyran‐2‐one ring opening and the formation of a strong conjugated compound 3.     

Synthesis of Bioactive Side‐Chain Analogues of TAN‐2483B

The fungal metabolite TAN‐2483B has a 2,6‐trans‐relationship across the pyran ring of its furo[3,4‐b]pyran‐5‐one core, which has thwarted previous attempts at its synthesis. We have now developed a chiral pool approach to this core and prepared side‐chain analogues of TAN‐2483B. The synthesis relies on ring expansion of a reactive furan ring‐fused dibromocyclopropane and alkynylation of the resulting pyran. The furan ring is constructed by palladium‐catalysed carbonylative lactonisation. Various side‐chains are appended through Wittig‐type chemistry. The prepared analogues showed micromolar activity towards cancer cell lines HL‐60, 1A9 and MCF‐7 and certain human disease‐relevant kinases, including Bruton's tyrosine kinase (Btk).     

Synthesis of Prenyl‐ and Geranyl‐Substituted Carbazole Alkaloids by DIBAL‐H Promoted Reductive Pyran Ring Opening of Dialkylpyrano[3,2‐a]carbazoles

The DIBAL‐H promoted reductive pyran ring opening of dialkylpyrano[3,2‐a]carbazoles provides a direct access to a broad range of prenyl‐ and geranyl‐substituted carbazoles. Formation of a pyran ring followed by reductive ring opening represents a new method for the introduction of prenyl and geranyl groups. In the course of the present work, we achieved the first total syntheses of the following eight carbazole alkaloids: clauraila‐E, 7‐hydroxyheptaphylline, 7‐methoxyheptaphylline, mukoenine‐B (clausenatine‐A), mukoenine‐A (girinimbilol), mahanimbinol (mahanimbilol), euchrestine‐A, and isomurrayafoline‐B.     

Analysis of the ambruticin and jerangolid gene clusters of Sorangium cellulosum reveals unusual mechanisms of polyketide biosynthesis

Ambruticins and jerangolids are structurally related antifungal polyketides produced by Sorangium cellulosum strains. Comparative analysis of the gene clusters and characterization of compounds produced by gene knockout strains suggested hypothetical schemes for biosynthesis of these compounds. Polyketide synthase (PKS) architecture suggests that the pyran ring structure common to ambruticins and jerangolids forms by an intramolecular reaction on a PKS-bound intermediate. Disrupting ambM, encoding a discrete enzyme homologous to PKS C-methyltransferase domains, gave 15-desmethylambruticins. Thus, AmbM is required for C-methylation, but not pyran ring formation. Several steps in the post-PKS modification of ambruticin involve new enzymology. Remarkably, the methylcyclopropane ring and putative carbon atom excision during ambruticin biosynthesis apparently occur on the PKS assembly line. The mechanism probably involves a Favorskii rearrangement, but further work is required to elucidate these complex events.     

Crystal structure of koraiol — A sesquiterpene alcohol with a new type of carbon skeleton from the oleoresin ofPinus koraiensis

An x-ray structural investigation has been made of a new sesquiterpene alcohol — koraiol — in the form of its complex with pyridine (2:1). The cyclobutane rings are nonplanar and the foldings of rings A and B amount to 17 and 31°, respectively. The seven-membered ring has the chair form.     

Unprecedented [5.5.5.6]Dioxafenestrane Ring Construction in Fungal Insecticidal Sesquiterpene Biosynthesis

Fenestranes, a specific class of natural products, contain four fused rings that share a central quaternary carbon atom. The fungal natural product penifulvin A ( 1 ) is a potent insecticidal sesquiterpene that features the [5.5.5.6]dioxafenestrane ring. Although the chemical synthesis of 1 has been achieved recently, the enzymes catalysing the cyclization and oxidation of FPP to 1 remain unknown. In this work, we identified a concise pathway that uses only three enzymes to produce 1 . A new sesquiterpene cyclase (PeniA) generates the angular triquinane scaffold silphinene ( 6 ). A cytochrome P450 (PeniB) and a flavin‐dependent monooxygenase (PeniC) catalyse a series of oxidation reactions to transform 6 into 1 , including oxidation of the C15 methyl group to a carboxylate moiety, oxidative coupling of the C15 carboxylate and the C1‐C2 olefin to form a γ‐lactone, and Baeyer–Villiger oxidation to form a δ‐lactone. Our results demonstrate the highly concise and efficient ways in which fungal biosynthetic pathways can generate complex sesquiterpene scaffolds.     

The isolation and structure elucidation of a new sesquiterpene lactone from the poisonous plant Coriaria japonica (Coriariaceae)

A new sesquiterpene lactone named coriarin was isolated from achenes (seeds) of Coriaria japonica (Coriariaceae) along with known constituents tutin, dihydrotutin and corianin, and its structure was deduced on a spectroscopic basis. The structure of coriarin was finally confirmed by the base-catalized chemical conversion of tutin into coriarin, in which the lactone ring linkage was transposed from C-3 to C-2. Chemical investigation of sarcocarps was also undertaken in parallel, but neither sesquiterpene lactones nor related constituents were obtained. The results indicate that sesquiterpene lactones occur only in achenes of C. japonica berry, as is the case in other Coriaria species.     

Halichonadins K and L, new dimeric sesquiterpenoids from a sponge Halichondria sp

Two new structurally unique dimeric sesquiterpenoids, halichonadins K (1) and L (2), were isolated from an Okinawan marine sponge Halichondria sp. The structures of 1 and 2 were elucidated on the basis of spectroscopic analysis including a single crystal X-ray diffraction analysis and chemical conversion. Halichonadins K (1) and L (2) are homodimers of the eudesmane sesquiterpene linked with a piperidine ring through amide bonds. Halichonadin K (1) showed moderate cytotoxicity against KB cells.     

The crystal and molecular structure of delta-9-tetrahydrocannabinolic acid b.

The crystal and molecular structure of the title compound C-22H-30O-4, has been determined by X-ray methods using 1106 reflections above background level collected by counter methods. The crystals are orthorhombic, space group P2-12-12-1 with cell dimensions a equals 16.514(2) A; b equals 14.324(2) A; c equals 8.744(1) A; there are four molecules per unit cell. The structure was refined to an R of 0.084 (weighted R-w equals 0.068). The cyclohexene and the pyran part of the molecule occurs in the half-chair conformation. The bond distances and angles, and a slight twist of the benzene ring, indicate considerable stains in the aromatic system. Both the phenolic and carboxylic group are significantly out of the plane through the aromatig ring. The angle between this plane and a plane through the cyclohexene ring is 37.7 degrees. The pentyl sidechain occurs in an extended gauche conformation, and the thermal parameters of this part of the molecule are very high. The molecules are held together by van der Waals forces in the c-directions, and hydrogen bonds (2.688 A) from phenolic to carboxylic groups in the a-b plane. There is a short ultra-molecular hydrogen bond (2.490 A) from the carboxylic group to the pyran oxygen.     

吲哚啉螺萘并吡喃的合成和时间分辩光谱研究

螺萘并吡喃类化合物是一类重要的有机光致变色化合物,因可用作光敏、光信息和光记录材料,而引起人们的研究兴趣．其中对螺苯并吡喃和螺嗪两类化合物的开环机理有较多的文献报道［１,２］,而对螺萘并吡喃的研究则少得多．我们合成了３个螺萘并吡喃化合物（其中ＳＰ１...     

N—H...O and N—H...N interactions in three pyran derivatives

The three pyran structures 6‐methylamino‐5‐nitro‐2,4‐diphenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₅N₃O₃, (I), 4‐(3‐fluorophenyl)‐6‐methylamino‐5‐nitro‐2‐phenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₄FN₃O₃, (II), and 4‐(4‐chlorophenyl)‐6‐methylamino‐5‐nitro‐2‐phenyl‐4H‐pyran‐3‐carbonitrile, C₁₉H₁₄ClN₃O₃, (III), differ in the nature of the aryl group at the 4‐position. The heterocyclic ring in all three structures adopts a flattened boat conformation. The dihedral angle between the pseudo‐axial phenyl substituent and the flat part of the pyran ring is 89.97 (1)° in (I), 80.11 (1)° in (II) and 87.77 (1)° in (III). In all three crystal structures, a strong intramolecular N—H...O hydrogen bond links the flat conjugated H—N—C=C—N—O fragment into a six‐membered ring. In (II), molecules are linked into dimeric aggregates by N—H... O(nitro) hydrogen bonds, generating an R₂²(12) graph‐set motif. In (III), intermolecular N—H...N and C—H...N hydrogen bonds link the molecules into a linear chain pattern generating C(8) and C(9) graph‐set motifs, respectively.     

Synthesis of tricyclic phospholene oxides by cycloaddition of phosphorus halides with heterocyclic analogs of 1-vinyl-3,4-dihydronaphthalenes

Replacement of C-4 with a hetero substituent (NR,O,S) in the 1-vinyl-3,4-dihydronaphthalene system has provided a new type of diene for participation in the McCormack cycloaddition reaction with P(III) halides. The tricyclic phospholene oxides so obtained are the first to bear an additional heteroatom in the ring system. 1,2-Dihydro-7-methoxy-1-(p-toluenesulfonyl)-4-vinylquinoline is a stable solid that reacts with methylphosphonous dichloride to give, after hydrolysis of the cycloadduct, the 1,2,4,5-tetrahydro-1H-phospholo-[2,3-c]quinoline ring system. The dihydroquinoline moiety was aromatized by detosylation with potassium t-butoxide. The tendency of 4-vinyl-2H-benzopyran to dimerize was a serious complication in its use, and the cycloaddition with methylphosphonous dichloride proceeded only in low yield. The product, a 2,3,3a,4-tetra-hydrobenzo[3,2-d]pyran derivative, was a stable, easily purified and characterized substance. 4-Vinyl-2H-benzo[b]thiopyran was more stable than the pyran, but the phospholo derivative from reaction with methylphosphonous dichloride was more difficult to purify. All products were characterized by ¹³C-nmr spectroscopy.     

Fusopoltides B–E,new polyketides isolated from Fusarium solani B-18

Four new polyketides, fusopoltides B–E, were isolated, along with four known compounds, from Fusarium solani B-18 cultured on brown-rice. Fusopoltide B is a diastereomer of its co-isolated known compound, fusopoltide A, featuring a pentaleno[1,2-c]pyran ring system. Fusopoltide C and fusopoltides D–E are incorporated the first natural polyketides featured decahydro-pentaleno[1,2-c]pyran and pentaleno[1,2-c]furan ring systems, respectively. The structural assignments were established using comprehensive spectroscopic techniques, the modified Mosher's ester method, and electronic circular dichroism (ECD) calculations.     

N′-叔丁基-N′-取代苯甲酰基-N-(苯并二氢吡喃-5-甲酰基)肼的 设计合成及晶体结构

以间羟基苯甲酸为起始原料通过7步反应合成了15个新颖的N′-叔丁基-N′-取代苯甲酰基-N-(苯并二氢吡喃-5-甲酰基)肼类化合物. 中间体3-炔丙氧基苯甲酸甲酯在N,N-二乙基苯胺中发生克莱森重排后得到主要产物苯并吡喃-5-甲酸甲酯和副产物苯并吡喃-7-甲酸甲酯. 通过氢谱、元素分析或高分辨质谱确定了这些化合物的结构, 化合物1a的X射线单晶衍射分析发现苯并二氢吡喃的吡喃环与苯环不共平面, 其中的C(1)和C(2)分别位于相应苯环平面的两侧.