CH3CN H2O Research Articles

Cascade sensitive and selective fluorescence OFF–ON–OFF sensor for Cr3+ cation and F− anion

Cascade recognition of trivalent chromium cation (Cr3+) and fluoride anion (F−) via rhodamine-urea methacrylate-based fluorescent probe (RhBUA) and its subsequent cationic complex was reported. The non-fluorescent rhodamine derivatives can selectively detect Cr3+ cation over some other metal ions in CH3CN–H2O (90/10, v/v, pH 7.0) solutions with a 1:1 stoichiometry, leading to prominent fluorescence OFF–ON switching. The obtained RhBUA–Cr3+ complex can subsequently serve as a sensitive and selective chemosensor for F− ion. Complete signal quenching (fluorescence ON–OFF switching) can also be observed, ascribing to the extraction of Cr3+ cation and the resulting deformation of RhBUA–Cr3+ complex.

A colorimetric and ratiometric fluorescent turn-on fluoride chemodosimeter and application in live cell imaging: high selectivity via specific Si[sbnd]O cleavage in semi aqueous media and prompt recovery of ESIPT along with the X-ray structures

A ratiometric fluorescent turn-on probe for fluoride ion, based on modulation of the excited-state intramolecular proton transfer (ESIPT) process by chemodosimetric desilylation pathway is reported. The probe SNBT (silyl protected hydroxynaphthalene benzothiazole moiety) shows a significant increase of ratiometric absorption band at 440nm and emission band at 477nm by the deprotection of fluoride mediated silyl bond cleavage in CH3CN–H2O (8/2, v/v, 25°C). The test strips based on SNBT and F− are fabricated, which can act as a convenient and efficient F− test kits. Furthermore, the biological application shows that it can be very useful as a selective fluoride probe in the fluorescence imaging of living cells.

Metal-Induced Isomerization of a Molecular Strand Containing Contradictory Dynamic Coordination Sites

A new hydroxymethyl terminated pyrimidine-hydrazone (pym-hyz) ligand (L1) was synthesized with a central hyz-pyridine-hyz (hyz-py-hyz) motif replacing the usual hyz-pym-hyz unit, to create a molecular strand that underwent metal-induced isomerization with a minimal net change in ligand length. NMR spectroscopy showed that L1 had a horseshoe shape due to the hyz-py-hyz and pym-hyz bonds adopting transoid conformations. The ligand was successfully reacted with Pb(II), Zn(II), and Ag(I) salts in either CH3CN or CH3NO2 resulting in horseshoe-shaped M(n+)3L1A3n (where A = ClO4(-) or SO3CF3(-)) complexes in the solution phase. Crystals were grown from these solutions, the structures of which were highly dependent on the metal ion and solvent used, and were distinctly different from those seen in solution. The crystals grown from mixtures of Pb(ClO4)2·3H2O and L1 in either CH3CN or CH3NO2 resulted in the horseshoe-shaped [Pb3L1(ClO4)4(H2O)2](ClO4)2·CH3CN (1) complex or the {[Pb3L1(ClO4)4(H2O)](ClO4)2}∞·CH3NO2 (2) helical coordination polymer, respectively. The horseshoe-shaped [Pb3L1(SO3CF3)6]·CH3CN (3) complex was crystallized from a solution of Pb(SO3CF3)2·H2O and L1 in CH3CN, while the crystals grown from the solution of Zn(SO3CF3)2 and L1 in CH3CN consisted of the zigzag-shaped [Zn3L1(H2O)7](SO3CF3)6 (4) complex. The [Ag3(L1)2](SO3CF3)3 (5) double-helicate and the macrocycle-like [Ag6(L1)2](SO3CF3)6 (6) complex were crystallized from solutions of AgSO3CF3 and L1 in either CH3CN or CH3NO2, respectively.

New insight on the mechanism of the catalytic hydrogenation of nitrobenzene to 4-aminophenol in CH3CN–H2O–CF3COOH as a reusable solvent system. Hydrogenation of nitrobenzene catalyzed by precious metals supported on carbon

The preparation of 4-aminophenol via hydrogenation of nitrobenzene in a single liquid phase has been carried in the presence of different precious metal catalysts. The liquid phase is composed of CH3CN–H2O–CF3COOH, which can be easily distilled at low temperature, thus avoiding work-up operation. The yield of 4-aminophenol is in the range 45% and in the presence of sulfolane as promoter reaches almost 50%. The best result has been obtained in the presence of Pt/C as hydrogenation catalyst. The role of the solvent is strictly related to the selectivity to 4-aminophenol, since CH3CN decreases the hydrogenation activity compared to other solvent, CF3COOH promotes the formation of the desired product both via Bamberger rearrangement in solution as well by a surface catalyzed reaction, while H2O is responsible for 4-aminophenol formation in both reactions. Even though, nitrosobenzene and phenylhydroxylamine have not been observed, their reactivity suggest a complex pattern of reactions occurring either on the catalyst surface or in the solution. Indeed, formation of 4-aminophenol may occur both in solution, via acid catalyzed Bamberger rearrangement and on the catalyst surface by the formation of a surface Pt-nitrenium complex, which undergoes surface nucleophilic attack by H2O.

Efficient photocatalytic hydrogen evolution with end-group-functionalized cobaloxime catalysts in combination with graphite-like C3N4

The pyrene-functionalized cobaloxime–g-C3N4 system was active for hydrogen production in CH3CN–H2O mixed solvent with a highest TON of 281.

Structural diversity and fluorescent properties of CdII coordination polymers with 5-halonicotinates regulated by solvent and ligand halogen-substituting effect

Seven CdII coordination polymers have been prepared from CdCl2 and 5-halonicotinic acids (HL–X, X = F or Cl) in different solvent media using a similar layered diffusion method. A pair of polymorphic isomers [Cd(L–F)2]n (1 and 2) can be assembled from CH3CN–H2O and CH3OH–H2O systems, respectively, featuring the 3-D (3,5)-connected (4·62)(4·67·82) network (5-connected node for each CdII ion and 2- or 3-connected linker for the two different types of L–F− ligand) and the 3-D (3,6)-connected ant framework with the point symbol of (4·62)2(44·62·88·10). While in DMF–H2O solvent, a 2-D layered complex [Cd(L–F)Cl(DMF)]n (3) is obtained with the (3,5)-connected net of (3·4·5)(32·4·5·62·74) topology, where the chloride anion is involved in coordination. When the HL–Cl ligand is utilized instead of HL–F, the assembling reactions in CH3CN–H2O and DMF–H2O media lead to the 3-D (3,5)-connected network of [Cd(L–Cl)2]n (4) and the 2-D (3,5)-connected net of [Cd(L–Cl)Cl(DMF)]n (6), which are isostructural to complexes 1 and 3, respectively. [Cd(L–Cl)2(H2O)2]n (5) can be generated from the CH3OH–H2O medium, showing a 2-D (4,4) layered structure, and the similar reaction in the C2H5OH–H2O solvent will produce a 3-D coordination framework {[Cd(L–Cl)2(H2O)0.5](C2H5OH)0.75(H2O)0.25}n (7) with the (3,6)-connected (3·4·5)(32·44·55·62·72) net. These structural divergences can be ascribed to the significant solvent modulation and halogen-substituting effect of 5-halonicotinates. Furthermore, their solid-state properties such as thermal stability and fluorescence have also been investigated.

Tetraplatinum cluster complexes bearing hydrophilic anchors as precursors for γ-Al2O3-supported platinum nanoparticles

Tetraplatinum cluster complexes bearing hydrophilic anchors, [Pt4(μ-OCOCH3)4(μ-OCOC6H4OH-4)4] (2a), [Pt4(μ-OCOCH3)4(μ-OCOC6H4B(OH)2-4)4] (2b), and [Pt4(μ-OCOCH3)4(μ-OCOC6H4NH2-4)4] (2c), were successfully prepared by a selective substitution reaction of four in-plane acetates of [Pt4(μ-OCOCH3)8] (1) with the corresponding p-substituted benzoic acids. Solid-state structure determination of 2a revealed the 3D network structure through intermolecular hydrogen bonding between the hydroxy group of the p-hydroxybenzoate ligand and the oxygen atom of the carboxylate ligand of 2a. UV-vis analysis of 2a–c in CH3CN or CH3CN–H2O in the presence of γ-Al2O3 clearly indicated the adsorption efficiency of these platinum clusters on γ-Al2O3: 2a bearing a hydroxyl group and 2b bearing a B(OH)2 group were effectively deposited onto γ-Al2O3 from CH3CN solution, whereas less than 40% of 1 and 2c were chemically adsorbed onto γ-Al2O3. Highly dispersed and very small platinum nanoparticles (less than 1 nm) on γ-Al2O3 were obtained by thermal treatment of Pt4-deposited γ-Al2O3 at 500 °C.

The employment of a hydrophilic tris(morpholino)phosphine ligand in diiron propane-1,3-dithiolate complexes for potentially water-soluble iron-only hydrogenase active-site mimics

A tris(morpholino)phosphine (TMP) ligand was introduced into the diiron dithiolate complexes in order to improve the hydro- and protophilicity of the iron-only hydrogenase active site models. Mono- and di-TMP substituted diiron complexes, (μ-pdt)[Fe(CO)3][Fe(CO)2(TMP)] (2, pdt = 1,3-propanedithiolato) and (μ-pdt) [Fe(CO)2(TMP)]2 (3), were synthesized and spectroscopically characterized. The coordination configuration of 3 was determined by single X-ray analysis. Temperature-dependent 1H and 31P NMR spectroscopy studies provided insight into the interconversion of the irondithiacyclohexane ring and the rotation of the [Fe(CO)2PR3] moieties for 2 and 3 in solution. The electrochemical properties of 2 and 3 were investigated in pure CH3CN and CH3CN–H2O mixtures in the absence and presence of acetic acid. Hydrogen production and the dependence of current on acid concentration indicated that complexes 2 and 3 exhibited electrocatalytic activities for proton reduction in both pure and H2O-containing CH3CN solutions. The current sensitivities, i.e., electrocatalytic activities, were demonstrated to be greater in CH3CN–H2O mixtures than in pure CH3CN. The most effective electrocatalytic activities of 2 and 3 were observed with 10% added water.

A new off–on chemosensor for Al3+ and Cu2+ in two different systems based on a rhodamine B derivative

A new rhodamine B derivative colorimetric and fluorescent double-sensor 1 has been investigated in this work. The sensor can select for Al3+ and Cu2+ in different systems. It exhibits highly sensitive recognition towards Al3+ in ethanol–H2O (2:3, v/v) via a visible color change from colorless to pink and an appearance of orange fluorescence. Whereas, in CH3CN–H2O buffer (3:2, v/v), the sensor shows a significant fluorescent enhancement for Cu2+ over a wide range of tested metal ions. Finally, the sensor can be used to detect Al3+ and Cu2+ in natural water samples with a high accuracy.

A sample pretreatment strategy for pH-zone-refining counter-current chromatography

A sample pretreatment method using acid–base extraction was established for pH-zone-refining counter-current chromatography (CCC) to increase the yield of the target compound. As the most important step, selection of two-phase solvent system for pH-zone-refining CCC should follow some rules. One of these rules is that when pH of two-phase solvent system is around 2 (for an acidic analyte) or 10 (for a basic analyte), partition coefficient values of Kacid or Kbase should be much greater than 1. According to this rule, a new pretreatment method was developed that could substantially increase the yield of the target compound in pH-zone-refining CCC. The separation of the crude alkaloids extracted from the seeds of Sophora alopecuroides was selected as an example to show the advantage of this method. Before CCC separation, 20g of crude sample was extracted 3 times with the selected two-phase solvent system composed of MtBE–CH3CN–H2O (2:2:3, v/v), where pH of the upper phase was adjusted with triethylamine to 10. A 10g amount of the second basic extract thus obtained was subjected to pH-zone-refining CCC separation. As a result, 169mg of sophoramin and 696mg of sophoearpin were isolated from the second basic extract, where the yields have been doubled compared with those of the untreated sample (crude sample). Experimental results showed that the present method for pretreating the crude sample could produce substantially higher yields of target compounds in pH-zone-refining CCC.

Chalcone derivatives as fluorescence turn-on chemosensors for cyanide anions

Abstract Three o-hydroxy chalcone derivatives 1–3 with carbazolyl (1), pyrene (2) and 4-nitrobenzene (3) as terminal group have been synthesized. Their crystal structures, photophysical properties in CH3CN and recognition properties for cyanide anions have also been examined. The research indicates that the stronger electroaffinity of the chalcone derivative's β-unit is beneficial to Michael reaction and can improve the response rate of the compound to cyanide anions. These compounds are found to be able to recognize cyanide anions with fluorescence turn-on response. Especially, compound 3 with strong electron accepting group exhibits remarkable response to cyanide anions in CH3CN H2O (1:1, v/v) solution with a ca. 40-fold intensity enhancement.

ESIPT based dual fluorescent sensor and concentration dependent reconfigurable boolean operators

Probes 1 and 2 (CH3CN–H2O; 4:1) at pH 7.0 ± 0.1 (10 mM, HEPES) selectively bind with Zn2+ ions and give a new emission band at 490 nm. These can estimate 20 nM Zn2+ ions as the lowest detection limit. The determination of Zn2+ ions by probe 1 is not interfered by the presence of other metal ions viz. Na+, K+, Mg2+, Ca2+, Sr2+, Fe2+, Co2+, Ni2+, Cd2+, Ag+, Hg2+. However, in the case of probe 2 Cu2+ causes only the fluorescence quenching. In acetonitrile, the addition of different concentrations of Cu2+ (2 μM, 5 μM, 10 μM) and a fixed amount of F− (25 μM) to a solution of 2 (0.25 μM, CH3CN) elaborates Cu2+ ion concentration dependent NOR, INH and AND Boolean operators with three distinct emission channels at 585, 515 and 400 nm, respectively.

Two novel trivacant Keggin-type polytungstates supported manganese carbonyl derivatives synthesized by degradation of metastable [γ-XW10O36]8− (X = GeIV, SiIV)

Two novel trivacant Keggin-type polyoxometallate-based manganese carbonyl derivatives K(8)[(OC)(3)Mn(A-α-H(2)GeW(9)O(34))]·10H(2)O (1) and K(8)[(OC)(3)Mn(A-α-H(2)SiW(9)O(34))]·11H(2)O (2) have been synthesized by degradation of the metastable [γ-XW(10)O(36)](8-) (X = Ge(IV), Si(IV)) in CH(3)CN-H(2)O solvent (1 : 2, vol.) and structurally characterized by elemental analyses, IR spectra, thermogravimetric analysis, and single-crystal X-ray diffraction. X-ray diffraction analyses indicate that 1 and 2 are isomorphic and consist of a [(OC)(3)Mn](+) group and a trivacant [A-α-H(2)XW(9)O(34)](8-) fragment, which exhibit the first examples of trivacant Keggin-type metal carbonyl derivatives. Additionally, the electrocatalytic properties of both for NO(2)(-) oxidation have been investigated.

Efficient [FeFe] hydrogenase mimic dyads covalently linking to iridium photosensitizer for photocatalytic hydrogen evolution

Two [FeFe] hydrogenase mimics, [Fe(2)(μ-pdt)(CO)(5)L1] (L1 = PPh(2)SPhNH(2)) (Ph = phenyl) (2) and [Fe(2)(μ-pdt)(CO)(5)L2] (L2 = PPh(2)PhNH(2)) (3), and two molecular photocatalysts, [(CO)(5)(μ-pdt)Fe(2)PPh(2)SPhNHCO(bpy)(ppy)(2)Ir]PF(6) (bpy = bipyridine, ppy = 2-phenylpyridine) (2a) and [(CO)(5)(μ-pdt)Fe(2)PPh(2)PhNHCO(bpy)(ppy)(2)Ir](PF(6)) (3a), have been designed and synthesized, anchoring Ir(ppy)(2)(mbpy)PF(6) (mbpy = 4-methyl-4'-carbonyl-2,2'-bipyridine) (PS) to one of the iron centers of complexes 2 and 3 by forming amide bonds. Molecular dyads 2a, 3a and the intermolecular systems 2, 3 with PS have also been successfully constructed for photoinduced H(2) production using triethylamine (TEA) as a sacrificial electron donor by visible light (>400 nm) in CH(3)CN-H(2)O solution. The time-dependence of H(2) generation and spectroscopic studies suggest that the activity of H(2) evolution can be tuned by addition of a S atom to the phosphane ligand. The highest turnover numbers (TON) of hydrogen evolution obtained are 127, using 2a as a photocatalyst in a supramolecular system, and 138, based on catalyst 2 in a multi-component system. Density functional theory (DFT) computational studies demonstrate that the S atom in the second coordination sphere makes complex 2 accept an electron more easily than 3 and improves the activity in light-induced hydrogen production.

Nitrogen-containing polymers as potent ionogens for aqueous solutions of switchable ionic strength: application to separation of organic liquids and clay particles from water

Polymeric tertiary amines react reversibly with CO2 in the presence of water to form trialkylammonium-bicarbonate polyelectrolytes. These polyamines are useful as ionogens for “switchable water”, meaning an aqueous solution having switchable ionic strength. The performance of the polymeric ionogens in two different water purification applications was evaluated. Moderate results were obtained in the salting out of organic contaminants from aqueous solutions with up to 77% of CH3CN forced out from a 1 : 1 (w/w) mixture of CH3CN–H2O. However, very promising results were obtained in the sedimentation of clay particles. A notable enhancement in both the settling time required and the supernatant turbidity was observed even with low loadings of the polymers (>10 ppm). The addition of CO2 is required for the polymers to induce settling. Dimethylamino-functionalized polymethyl methacrylate proved to be the best polymer evaluated thus far in this process. In addition to enhancing the settling of both kaolinite and montmorillonite suspensions at different concentrations, it was also successfully shown to enhance the settling of oil sand tailings.

The reactivity of diarylmethyl carbocations within non-protic zeolites

The generation of diarylmethyl carbocations within non-protic zeolites (LiY, NaY, KY, RbY, CsY, and NaX) was carried out via laser excitation (266 nm or 266 nm / 308 nm) of diarylacetic acids. Rapid loss of CO2, followed by photochemical oxidation of the diarylmethyl radicals resulted in the formation of the diarylmethyl carbocations. The reactivity of the diarylmethyl carbocations was found to be highly dependent on the alkali metal counterion and the Si/Al ratio of the zeolite framework. Furthermore, the effect of various para-electron donating substituents (4-H, 3-CH3, 4-CH3, 4,4′-CH3, and 4-OCH3) on the diarylmethyl carbocation reactivity was investigated. Comparison of the Hammett plots constructed for the reactivity of the diarylmethyl carbocations in zeolites with those in solution (CH3CN–H2O (1:2) and TFE) showed decreased sensitivity of the electrophilic species towards para-electron donating substituents in the heterogeneous media. The leveling effect observed in the zeolite Hammett plots has been attributed to the presence of an isokinetic relationship, specifically, a low isokinetic temperature for the reaction of diarylmethyl carbocations with the aluminosilicate zeolite framework.

A new ortho-phenylenediamine-based cleft for selective sensing of H2PO4− and ATP

Ortho-phenylenediamine based chemosensor 1 has been designed and synthesized. The chemosensor 1 selectively binds H2PO4− in CH3CN showing excimer emission at 456 nm due to π–π stacking between the pendant naphthalene units. The sensor 1 also fluorometrically distinguishes ATP from ADP and AMP in CH3CN–H2O (1 : 1, v/v) at pH = 6.5.

Pyridinium-based symmetrical diamides as chemosensors in visual sensing of citrate through indicator displacement assay (IDA) and gel formation

The design and synthesis of pyridinium-based symmetrical diamides 1 and 2 along with their anion binding studies through 'indicator-diplacement assay' are reported. Both the chemosensors effectively respond in in CH(3)CN-H(2)O (4 : 1 v/v) at pH = 6.3 for the selective naked-eye detection of citrate. Additionally, chemosensor 2 (c = 6.29 × 10(-3) M) forms a stable gel only with citrate in CH(3)CN, which validates its visual sensing.

A new propanol derivative from marine Pseudomonas sp. M474

Marine microorganisms have proved to be rich sources of bioactive secondary metabolites, and numerous compounds with potent biological activities and unique chemical structures have been isolated [1]. As terricolous microorganisms, marine microorganisms are new and important sources of bioactive compounds, including terpenes, polyketides, flavonoids, peptides, alkaloids, and many unidentified and uncharacterized structures [2]. Marine Pseudomonas is also a new and important resource, and propanol derivatives are reported from them for the first time. In our screening program for bioactive principles from marine Pseudomonas, a new propanol derivative was isolated from the acetic ether extract of marine Pseudomonas sp. M474. In this paper, we report the isolation and structure elucidation of this new propanol derivative on the basis of analysis of the spectral data, including 1D and 2D NMR spectroscopic data. The strain M474 has been derived from sediment of Jiaozhou Bay in China. It was isolated on Gause s starch medium with incubation at 28 C. The pure culture was maintained on Gause s starch agar medium with K2Cr2O7 at 4 C. The strain forms a yellow soluble pigment. Due to its chemical and morphological features, as well as the 16S rRNA, the strain can be classified as a marine Pseudomonas species. The strain is deposited in the culture collection of marine microorganisms at the Institute of Oceanology, Chinese Academy of Sciences. The marine strain Pseudomonas sp. isolate M474 was inoculated from its slant agar culture on M2+ agar plates with 50% seawater. It formed yellow colonies with a gray aerial mycelium on incubation at 28 C. With fresh agar cultures of the strain, 100 1-L Erlenmeyer flasks each containing 250 mL of M2+ medium (set to pH 7.8 before sterilization) were inoculated and grown for 4 days at 28 C with shaking at 120 rpm. The entire culture broth was mixed with ca. 1 kg of diatomaceous earth and pressed through a pressure filter, and both filtrate and residue were extracted with acetic ether. The combined extracts were evaporated to dryness to yield 12 g of the crude extract. The crude extract was subjected to middle-pressure LC with methanol–H2O gradient to yield 32 fractions. Then the fraction (100 mg) was chromatographyed on a C8 half-preparative column (Zorbax columns, RX-C8, 9.4 mm 25 cm) using isocratic elution of CH3CN–H2O (30:70), yielding a novel propanol derivative (5 mg).

JBIR-52, a new antimycin-like compound, from Streptomyces sp. ML55

GRP78/Bip is a molecular chaperone in the endoplasmic reticulum (ER) induced by ER stress that promotes protein folding and has an important role as a survival factor in solid tumors by providing resistance to both chemotherapy and hypoglycemic stress.1 Thus, specific downregulators of GRP78 expression can reasonably be expected to become promising drugs in cancer chemotherapy.2 In the course of our screening program for downregulators of GRP78 expression, we have isolated versipelostatin A-F,3–11 prunustatin A,12,13 JBIR-04, -0514 and JBIR-06.15 Further screening resulted in the isolation of a new inhibitor designated as JBIR-52 (1, Figure 1) from culture of a JBIR-06 producer, Streptomyces sp. ML55.15,16 In this paper, we report the isolation, structure elucidation and brief biological activity of a new member of antimycin, 1. Streptomyces sp. ML55 was cultured on a rotary shaker (220 r.p.m.) at 27 1C for 5 days in 500-ml Erlenmeyer flasks containing 100 ml of a production medium consisting of 2% glycerol (Nacalai Tesque, Kyoto, Japan), 1% molasses (Dai-Nippon Meiji Sugar, Tokyo, Japan), 0.5% casein (Kanto Chemical, Tokyo, Japan), 0.1% polypepton (Nihon Pharmaceutical, Tokyo, Japan), 0.4% CaCO3 (Kozaki Pharmaceutical, Tokyo, Japan) (pH 7.2 before sterilization). The mycelium from the culture broth (2 l) was extracted with Me2CO (400 ml). After concentration in vacuo, the residue was extracted twice with EtOAc. The organic layer was dried over anhydrous Na2SO4, and concentrated in vacuo. The dried residue (1.99 g) was applied to normal-phase MPLC (Purif-Pack SI-60, size:60, Moritex, Tokyo, Japan) and developed with a n-hexane–EtOAc linear gradient system (0–100% EtOAc), and peak detection was carried out by UV absorption at 254 nm. The 60–75% EtOAc eluate (470 mg) was further chromatographed on normal-phase MPLC (Purif-Pack SI-60, size:20, Moritex) with n-hexane–EtOAc (80:20). A portion (44.5 mg) of the fraction (388 mg) including both 1 and JBIR-06 was finally purified by preparative reversed-phase HPLC using an L-column2 ODS (20 i.d. 150 mm, Chemical Evaluation Research Institute, Tokyo, Japan) with 60% CH3CN–H2O containing 0.1% formic acid (flow rate, 9.5 ml min 1) to yield 1 (1.7 mg, retention time (Rt) 28.0 min) and JBIR-06 (2.3 mg, Rt 37.0 min). Compound 1 was obtained as a white powder ([a]D +40.0, c 0.07, 29 1C in MeOH, UV (MeOH) lmax (e) 225 (22 500), 336 nm (4050)). The IR spectrum of 1 revealed the characteristic absorptions of esters (nmax 1750, 1280 cm 1), amide (nmax 1645 cm 1), hydroxyl and/or amide NH (nmax 3400 cm 1) groups. The HR electron spray ionization MS spectrum of 1 gave the (M+H)+ ion at m/z 549.2429 (calcd. for C27H37N2O10, 549.2448) consistent with a molecular formula of C27H36N2O10. Direct connectivity between protons and carbons was established by the heteronuclear single quantum coherence spectrum and the 13C and 1H NMR spectral data for 1 are shown in Table 1. The observed double-quantum-filtered (DQF)-COSY and constant time heteronuclear multiple bond correlation (HMBC)17 spectra established four partial structures. The sequence from an oxymethine proton 2-H (dH 5.46) to 11-H (dH 1.64), which in turn coupled to two methyl protons 12-H (dH 0.95) and 13-H (dH 0.94), through 10-H (dH 1.84, 1.72) in the DQF-COSY spectrum established a 3-methyl-1-oxybutyl moiety. A doublet methyl proton 27-H (dH 1.33) and a low-field shifted methine proton 9-H (dH 3.32), which were spin–spin coupled to each other, were each long-range coupled to an ester carbonyl carbon C-8 (dC 170.2) and a ketone carbonyl carbon C-1 (dC 202.1), which in turn long-range coupled to 2-H and 10-H. These HMBC correlations indicated the successive connectivity of C-2, C-1, C-9 and C-8 as shown in Figure 1b. Thus, a 2,6-dimethyl-3-oxo-4-oxyheptanoic acid moiety was elucidated as a partial structure of 1 (Figure 1b). The proton sequence between the aromatic protons 22-H (dH 8.58), 23-H (dH 6.97) and 24-H (dH 7.36) indicated the presence of a 1,2, 3-trisubstituted benzene ring moiety. An amide proton 21-NH (dH 7.97) was coupled to an aldehyde proton 25-H (dH 8.52), which was