Gluconobacter mediated synthesis of amino sugars

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that play important roles in physiological and pathological conditions. Both gelatinases (MMP-2 and -9) and membrane-type 1 MMP (MMP-14) are important targets for inhibition, since their roles in various diseases, including cancer, have been well established. We describe herein a set of mechanism-based inhibitors that show high selectivity to gelatinases and MMP-14 (inhibitor 3) and to only MMP-2 (inhibitors 5 and 7). These molecules bind to the active sites of these enzymes, initiating a slow binding profile for the onset of inhibition, which leads to covalent enzyme modification. The full kinetic analysis for the inhibitors is reported. These are nanomolar inhibitors (Ki) for the formation of the noncovalent enzyme-inhibitor complexes. The onset of slow binding inhibition is rapid (k(on) of 10(2) to 10(4) M(-1) s(-1) and the reversal of the process is slow (k(off) of 10(-3) to 10(-4) s(-1)). However, with the onset of covalent chemistry with the best of these inhibitors (e.g. inhibitor 3), very little recovery of activity (<10%) was seen over 48 h of dialysis. We previously reported that broad spectrum MMP inhibitors like GM6001 enhance MT1-MMP-dependent activation of pro-MMP-2 in the presence of tissue inhibitor of metalloproteinases-2. Herein, we show that inhibitor 3, in contrast to GM6001, had no effect on pro-MMP-2 activation by MT1-MMP. Furthermore, inhibitor 3 reduced tumor cell migration and invasion in vitro. These results show that these new inhibitors are promising candidates for selective inhibition of MMPs in animal models of relevant human diseases.

Conjugation, as an essential chemical term used to describe electron delocalization, can be roughly grouped into two categories, through-bond conjugation (TBC) and through-space conjugation (TSC). A hybrid conjugation system integrating both TBC and TSC is rarely studied and utilized, for lack of a well-established model and difficulty of structure modification and property tuning, despite its theoretical significance and potential applications. Herein, various foldamers with a tetraphenylethene (TPE) core are employed as hybrid conjugation models to investigate structure-property correlation by introducing heterocycles of furan/thiophene into the π-stacking TSC component. For comparison, two kinds of TPE-cored foldamers with different stacking models, a benzene-heterocycle stacking model and a benzene-benzene stacking model, are designed. Combining experimental measurements and theoretical calculations, the impact of benzene-heterocycle interaction on the hybrid conjugation natures and photophysical properties has been studied systematically. The results reveal that the benzene-heterocycle stacking model can fabricate a hybrid conjugation nature with an improved TSC component to make a more dominant contribution to the electronic transition natures than the benzene-benzene stackingmodel, leading to the distinguishing photophysical behavior. This work provides valuable guidance for the design of new functional materials with hybrid conjugation systems. © 2022 The authors. All right reserved.

Euphorbia sororia Schrenk, an annual herbaceous plant of the genus Euphorbia L. (Euphorbiaceae), is distributed mainly in Central Asia and the Hetian region of Xinjiang in China. Having diuretic, antihypertensive, antiasthmatic, and purgative properties, it is a commonly used medicinal material of Uighur doctors and has been recorded in the pharmacography of Uighur [1]. In this work, we report on the chemical constituents of the aerial parts of E. sororia. The 95% EtOH extracts of the plant were partitioned with EtOAc and n-BuOH, and the corresponding residues, submitted to different chromatographic techniques, such as silica gel, Sephadex LH-20, and MCI-gel columns, led to the isolation and identification of nine chemical compounds. Their structures were identified as astragalin (1), kaempferol-3-O-D-galactoside (2), rutin (3), 24-methylene cycloartanol (4), heptacosanol (5), octacosanol (6), adenosine (7), -sitosterol (8), and daucosterol (9), respectively. Compounds 1, 4–6 are reported from the plant for the first time [2, 3]. All the purified compounds were identified by spectral analysis (1H and 13C NMR, EI-MS) and by comparison with the literature data [2–8]. Plant Material. The plant materials were collected in the Tacheng region of Xinjiang (June 2004) and authenticated by Prof. Zhang Yan Fu (Xinjiang Institute of Materia Medica, China) for E. sororia. Extraction and Isolation. The air-dried aerial parts of E. sororia (10 kg) were extracted three times with 95% aqueous ethanol (v/v) (50 L 3 h) at reflux to give a crude extract (1.8 kg) after concentration at reduced pressure. The extract was suspended in water and extracted with petroleum ether, EtOAc, and n-BuOH successively. The petroleum ether fraction (45 g) was subjected to repeated silica gel column chromatography and eluted with petroleum ether–EtOAc gradient to give compounds 4–7. The EtOAc fraction (45 g) was subjected to repeated silica gel column chromatography and eluted with petroleum ether–EtOAc–MeOH gradient to give compounds 8 and 9. The n-BuOH fraction (30 g) was chromatographed over an AB-8 macroporous absorbent resin column with gradient elution by water, 10% EtOH, and 30% EtOH successively. The 30% EtOH fraction (10 g) was chromatographed over Sephadex LH-20 and MCI gel columns and eluted with H2O–CH3OH in a gradient manner to afford compounds 1–3. Astragalin (1). C21H20O11, light yellow needles (MeOH), mp 163–165 C. HCl-Mg reducion reaction is positive. 1H NMR (600 MHz, CD3OD, , ppm, J/Hz): 8.05 (2H, d, J = 8.4, H-2 , 6 ), 6.88 (2H, d, J = 8.4, H-3 , 5 ), 6.20 (1H, d, J = 1.2, H-6), 6.40 (1H, d, J = 1.2, H-8), 5.35 (1H, d, J = 6.8, H-1 ). 13C NMR (150 MHz, CD3OD, , ppm): 156.6 (C-2), 133.4 (C-3), 177.0 (C-4), 160.1 (C-5), 98.2 (C-6), 164.2 (C-7), 93.7 (C-8), 156.6 (C-9), 104.2 (C-10), 120.9 (C-1 ), 131.0 (C-2 , 6 ), 115.1 (C-3 , 5 ), 160.1 (C-4 ), 101.1 (C-1 ), 74.5 (C-2 ), 76.4 (C-3 ), 71.9 (C-4 ), 76.6 (C-5 ), 60.9 (C-6 ). Kaempferol-3-O-D-galactoside (2). C21H20O11, yellow powder (MeOH), mp 231–232 C. IR (KBr, , cm–1): 3455, 3173, 1656, 1590, 1558, 149, 1302, 1264, 1081, 798. 1H NMR (600MHz, CD3OD, , ppm, J/Hz): 12.50 (H, s, 5-OH), 8.08 (2H, d, J = 9.0, H-6 ), 6.84 (2H, d, J = 9.0, H-3 , 5 ), 6.40 (1H, d, J = 1.2, H-8), 6.20 (1H, d, J = 1.2, H-6), 5.35 (1H, d, J = 7.2, H-1 ). 13C NMR (150 MHz, CD3OD, , ppm, J/Hz): 176.6 (C-4), 164.2 (C-7), 160.1 (C-5), 159.1 (C-4 ), 156.3 (C-9), 156.3 (C-2), 133.2 (C-3), 131.4 (C-2 , 6 ), 120.2 (C-1 ), 114.6 (C-3 , 5 ), 104.4 (C-10), 102.0 (C-1 ), 98.2 (C-6), 93.7 (C-8), 75.7 (C-5 ), 73.9 (C-3 ), 71.7 (C-2 ), 68.0 (C-4 ), 60.1 (C-6 ). 24-Methylene Cycloartanol (4). C41H52O, white amorphous powder (CHCl3), mp 122–123 C. EI-MS m/z 441 [M + H]+. 1H NMR (600 MHz, CDCl3, , ppm, J/Hz): 0.33, 0.55 (each 1H, d, J = 4.2, H2-19), 0.81 (3H, s, H3-30), 0.90 (3H, s, H3-28), 0.90, (3H, d, J = 6.5, H3-21), 0.97 (6H, s, H3-18, 29), 1.02 (3H, d, J = 6.9, H3-27), 1.03 (3H, J = 6.9, H3-26), 4.62, 4.67 (each 1H, br.s, H2-31). 13C NMR (150 MHz, CDCl3, , ppm, J/Hz): 32.0 (C-1), 30.40 (C-2), 78.9 (C-3), 40.5 (C-4), 47.1

1H, 13C, 15N and 31P NMR was applied to a study of free and protein-bound flavins in order to obtain a better insight into the mechanism by which the function of the flavin coenzyme is "tuned" upon binding to apoflavoproteins. A thorough 13C and 15N investigation of free flavins provided a detailed view on the effects of sterical hindrance and polarization on the structure of oxidized and reduced flavins. Moreover, this study resulted in a semi-empirical basis for the interpretation of NMR data obtained on protein-bound flavins. Remarkable results of the study of free flavins are the fact, that oxidized isoalloxazine is not fully planar in an apolar medium, and that fully reduced isoalloxazine is more planar than believed up till now. Unsubstituted reduced isoalloxazine in water has an almost fully sp 2hybridized N(10) and an N(5) atom which is approximately 70% sp 2hybridized. Upon modification the hybridization of N(5) and N(10) can be modulated rather independently due to steric hindrance. The so-called "butterfly" motion has a low activation barrier, which is probably an important feature for the mentioned tuning mechanism.Flavodoxin from Megasphaeraelsdenii is the protein which is most extensively studied in this thesis. By a 13C relaxation study it was shown that the isoalloxazine ring is strongly immobilized upon binding to apoflavodoxin. Also the phosphate group of FMN is strongly immobilized in the interior of the protein. Moreover, the phosphate group is dianionic in the complex, regardless of the redox state of bound FMN. Based on the NMR data, it was shown that the redox potential for the transition semiquinone/hydroquinone is mainly governed by charge interactions. For the first time a quantification of the redox potential modification by the apoprotein could be established, thereby showing that, contrary to literature reports, the redox potential modulation is not governed by steric effects exerted on the isoalloxazine moiety. Both by 31P NMR and 1H NMR it was shown that M.elsdenii flavodoxin acts as a one-electron transferring protein shuttling between the semiquinone and hydroquinone state, because the oxidized state is ruled out as a biologically relevant redox state in this protein due to the introduction of a high activation barrier between the oxidized and semiquinone state. Moreover, the electron transfer mechanism is of an outer sphere type. Based on the NMR data some arguments are presented that a specific complex formation between M.elsdenii flavodoxin and the electron donor or acceptor is not needed for an effective electron transfer. An important part of the active center of M.elsdenii flavodoxin was elucidated using time resolved photochemically induced dynamic nuclear polarization (CIDNP) and modern two-dimensional NMR techniques. The use of the paramagnetic semiquinone state in combination with 2D NMR techniques allowed the generation of NMR spectra of only the active center. Complete assignments were given in both the oxidized and the hydroquinone state for Trp-91, Ala-56 and Tyr-89, which are all very close to the isoalloxazine ring. It was shown that the relative position of Trp-91 with respect to the prosthetic group is slightly different in the two redox states. The active center of flavodoxin from M.elsdenii and Clostridium MP appear to be similar. The only small difference between results of the crystallographic study on Clostridium MP flavodoxin and 1H NMR results on M.elsdenii flavodoxin was observed for the relative position of Ala-56 and Tyr-89.A detailed 13C and 15N NMR study was performed on the complex of riboflavin and Riboflavin Binding Protein from the egg yolk and egg white. Subtle information on hydrogen bonding, conformation of the isoalloxazine ring and solvent accessibility were obtained in oxidized and reduced state. As far as the results could be compared with reported binding studies of riboflavin analogues, the results appear to be in excellent agreement. The pyrimidine ring is exposed to solvent, except for 0(4α) in both redox states. N(10) is forced into the molecular plane, which in turn probably causes N(1) to be somewhat out of the plane. The NMR results are consistent with a partial opening of the protein at pH 6 and a more stable conformation at pH 9. Based on the NMR results a possible function for the complex in the embryonic development is suggested.As an example of the class of dehydrogenases, lipoamide dehydrogenase from Azotobacter vinelandii was studied by 13C NMR. In the oxidized state hydrogen bonds exist to 0(2α) and 0(4α), but the polarization of the isoalloxazine ring probably does not extend to the N(10) atom. The 4 electron reduced protein (both the essential disulfide and the flavin are reduced) contains an essentially planar N(10) atom, and again hydrogen bonds to 0(2α) and 0(4α). The 2 electron reduced protein (EH 2 ) appeared to be particularly interesting. It consists of an equal mixture of protein in which the disulfide is reduced and the flavin oxidized, and protein in which the disulfide is oxidized and the flavin reduced. The results allowed a detailed description of the electronic structure of the two-electron reduced protein. From the NMR results it is concluded that the redox potential of both centers is roughly the same. The results show that if the disulfide is reduced one thiol group is present as an anionic thiol group and extremely close to the C(4a) atom of the flavin. The exchange of reduction equivalents between the two redox centers in EH 2 is slow (<5 s -1). In combination with reported kinetic data, it became evident that NAD +accelerates considerably the exchange of reduction equivalents between the disulfide and the flavin. The results show that this transfer must be implemented in the reaction cycle and offer a nice explanation of some "anomalous" kinetic data.As an example of the class of hydroxylases, p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens was studied by 1C NMR. Without substrate the isoalloxazine ring is probably exposed to solvent. Upon substrate binding a drastic change of the polarization of C(2) occurs, which is in accord with the published enzyme-substrate complex as revealed by crystallographic methods. It is suggested, that the active center without substrate is rather mobile in order to facilitate the binding of substrate. A conformational change accompanies the binding of substrate. The active center, as present in the oxidized enzyme-substrate complex, is probably already essentially formed upon reduction of the enzyme in the absence of substrate, which explains the drastically decreased binding rate of substrate after reduction. Upon complex formation' with substrate in the reduced state the N(5) is forced into the molecular plane of flavin. Some arguments are presented suggesting that the sp 2hybridization degree of N(5) and N(10) are the main factors which govern the reactivity (or "activation") of oxygen, but not the πelectron density at the C(4a) center of flavin. An electron transfer from the hydroquinone state towards oxygen probably precedes the formation of a C(4a) peroxyflavin by radical pair combination.

The application of NMR spectroscopy to complex mixture analysis and, in particular, to metabolomics is limited by the low sensitivity of NMR. We recently showed that dissolution dynamic nuclear polarization (d-DNP) could enhance the sensitivity of 13C NMR for complex metabolite mixtures, leading to the detection of highly sensitive 13C NMR fingerprints of complex samples such as plant extracts or urine. While such experiments provide heteronuclear spectra, which are complementary to conventional NMR, hyperpolarized 1H NMR spectra would also be highly useful, with improved limits of detection and compatibility with the existing metabolomics workflow and databases. In this technical note, we introduce an approach capable of recording both 1H and 13C hyperpolarized spectra of metabolite mixtures in a single experiment and on the same hyperpolarized sample. We investigate the analytical performance of this method in terms of sensitivity and repeatability, and then we show that it can be efficiently applied to a plant extract. Significant sensitivity enhancements in 1H NMR are reported with a repeatability suitable for metabolomics studies without compromising on the performance of hyperpolarized 13C NMR. This approach provides a way to perform both 1H and 13C hyperpolarized NMR metabolomics with unprecedented sensitivity and throughput.

Nuclear magnetic resonance, vibrational spectroscopic studies, physico-chemical properties and computational calculations on (nitrophenyl) octahydroquinolindiones by DFT method

Arabidopsis thaliana (L.) Heynh. has become a model system for studying many aspects of plant biology and biochemistry. Studies on the chemical constituents have previously led to the isolation of flavonoids [1, 5], oxylipins [2–5], and alkaloids [5] from A. thaliana. The wild herbs of Arabidopsis thaliana were collected from Jiande, Zhejiang, P. R. China, in 2009. A voucher specimen was deposited in the Herbarium of Materia Medica, School of Pharmacy, Second Military Medical University, Shanghai, P. R. China. The dried and powdered material (5 kg) was extracted with 95% EtOH at room temperature. The combined extract was then suspended with water and extracted three times with ethyl acetate, then purified by column chromatography with silica gel to yield compounds 1–7. The compounds were identified using UV, IR, and NMR spectral data and determined as camalexin (1) [6], methyl 1-methyl-1H-indole-3-carboxylate (2) [7, 8], methyl 1H-indole-3-carboxylate (3) [9, 10], 1-methoxy-3-indolecarbaldehyde (4) [11, 12], 4-hydroxy-3-methoxybenzaldehyde (5) [13, 14], phthalic acid isodibutyl ester (6) [15, 16], and -tocopherol (7) [17]. Compounds 1–3 and 5–7 were isolated from A. thaliana for the first time. The 13C NMR signals of compounds 2 were assigned by 1D and 2D NMR for the first time. Camalexin (1). Colorless needles, mp 135–139 C. 1H NMR (400 MHz, CDCl3, , ppm, J/Hz): 9.40 (br.s, N-H), 8.27 (d, J = 7.84, H-4), 7.88 (d, J = 3, H-4 ), 7.84 (d, J = 2.5, H-2), 7.44 (m, H-7), 7.35 (m, H-6), 7.34 (m, H-5), 7.29 (d, J = 3, H-5). 13C NMR (100 MHz, CDCl3, , ppm): 163.6 (s, C-2 ), 142.2 (d, C-2), 136.5 (s, C-7a), 124.9 (s, C-3a), 124.6 (d, C-4 ), 123.1 (d, C-5), 121.4 (d, C-6), 120.4 (d, C-4), 116.1 (d, C-5 ), 112.0 (s, C-3), 111.8 (d, C-7). Methyl 1-Methyl-1H-indole-3-carboxylate (2). White powder. 1H NMR (400 MHz, CDCl3, , ppm): 8.20 (m, H-4), 7.80 (s, H-2), 7.38 (m, H-7), 7.34 (m, H-5), 7.31 (m, H-6), 3.93 (s, OCH3), 3.85 (s, NCH3). 13C NMR (100 MHz, CDCl3, , ppm): 165.5 (COOCH3), 137.2 (s, C-7a), 135.2 (d, C-2), 126.6 (s, C-3a), 122.8 (d, C-5), 121.9 (d, C-6), 121.7 (d, C-4), 109.8 (d, C-7), 106.9 (s, C-3), 51.0 (q, OCH3), 33.5 (NCH3). Methyl Indole-3-carboxylate (3). White powder. 1H NMR (400 MHz, CDCl3, , ppm, J/Hz): 8.65 (br.s, N-H), 8.21 (m, H-4), 7.96 (d, J = 1.12, H-2), 7.45 (m, H-7), 7.32 (m, H-5), 7.30 (m, H-6), 3.95 (s, OCH3). 13C NMR (100 MHz, CDCl3, , ppm): 165.6 (s, COOCH3), 135.9 (s, C-7a), 130.9 (d, C-2), 125.8 (s, C-3a), 123.3 (d, C-5), 122.1 (d, C-6), 121.6 (d, C-4), 111.5 (d, C-7), 108.9 (s, C-3), 51.1 (q, OCH3). Compound 3 displayed significant growth inhibition against K562 human chronic leukemia [18]. 1-Methoxy-3-indolecarbaldehyde (4). Yellow oil. 1H NMR (400 MHz, CDCl3, , ppm): 9.99 (CHO), 8.34 (m, H-7), 7.92 (s, H-2), 7.51 (m, H-4), 7.41 (m, H-6), 7.36 (m, H-5), 4.20 (s, OCH3). 13C NMR (100 MHz, CDCl3, , ppm): 184.2 (s, CHO), 132.6 (d, C-7), 131.7 (d, C-2), 124.6 (d, C-5), 123.5 (d, C-4), 122.2 (s, C-3a), 121.6 (s, C-7a), 114.1 (s, C-3), 108.7 (d, C-6), 66.9 (q, OCH3). 4-Hydroxy-3-methoxybenzaldehyde (5). White powder. 1H NMR (400 MHz, CDCl3, , ppm, J/Hz): 9.85 (CHO), 7.44 (1H, d, J = 1.6, H-2), 7.07 (1H, d, J = 8.5, H-5), 7.46 (1H, dd, J = 8.5, 1.6, H-6), 6.20 (br.s, 4-OH), 3.99 (s, OCH3). 13C NMR (100 MHz, CDCl3, , ppm): 190.6 (s, CHO), 151.6 (s, C-4), 147.1 (s, C-3), 129.9 (s, C-1), 127.5 (d, C-6), 114.4 (d, C-2), 108.7 (d, C-5), 56.1 (q, OCH3).

Structure of the major degradant of ezetimibe

Pagoda[5]arene (P5), which is composed of five 2,6-dimethoxylanthracene (2,6-DMA) subunits bridged by methylene groups at 1,5 positions, was conveniently synthesized in 43% by trifluoroacetic acid ...

Directed evolution was applied to the beta-glycosidase of Thermus thermophilus in order to increase its ability to synthesize oligosaccharide by transglycosylation. Wild-type enzyme was able to transfer the glycosyl residue with a yield of 50% by self-condensation and of about 8% by transglycosylation on disaccharides without nitrophenyl at their reducing end. By using a simple screening procedure, we could produce mutant enzymes possessing a high transferase activity. In one step of random mutagenesis and in vitro recombination, the hydrolysis of substrates and of transglycosylation products was considerably reduced. For certain mutants, synthesis by self-condensation of nitrophenyl glycosides became nearly quantitative, whereas synthesis by transglycosylation on maltose and on cellobiose could reach 60 and 75%, respectively. Because the most efficient mutations, F401S and N282T, were located just in front of the subsite (-1), molecular modeling techniques were used to explain their effects on the synthesis reaction; we can suggest that repositioning of the glycone in the (-1) subsite together with a better fit of the acceptor in the (+1) subsite might favor the attack of a glycosyl acceptor in the mutant at the expense of water. Thus these new transglycosidases constitute an interesting alternative for the synthesis of oligosaccharides by using stable and accessible donor substrates.

Experimental and theoretical investigations of 4-chloro-N-(2-methoxyphenyl)benzamidoxime

The genus Achillea (Compositae, Anthemideae) comprises over 100 species worldwide, which are mainly distributed in the northern hemisphere. Among them, about ten species were found in China: A. alpina, A. millefolium, A. wilsoniana, A. setacea, A. asiatica, A. impatiens, A. ledebouri, A. ptarmicoides, A. acuminate, and A. salicifolica [1]. A. alpina has been used by local people, as a traditional herbal medicine to treat acute inflammation and pharmacological studies show that it has anti-inflammatory, antipyretic, and sedative properties. Some organic acids, monoand sesquiterpenoids, flavonoids, and polyacetylene compounds have been reported from this plant [2–8]. The aerial parts of A. alpina were collected in August 2010 from Jilin Province, China, and identified by Prof. Jianhua Wang, Pharmacognosy Laborary, School of Pharmaceutical Sciences, Hebei Medical University. Dry pieces of the aerial part of A. alpina (8 kg) were extracted with 95% ethanol at room temperature. After evaporation of the solvent under reduced pressure, the residue was suspended in water and extracted with petroleum ether, CH2Cl2, EtOAc, and n-BuOH, successively. The CH2Cl2 fraction (90 g) was subjected to silica gel column chromatography and eluted with petroleum ether–CH3COCH3 (100:1 1:1). Fractions 66 to 91 and 92 to 144 afforded 1 (26.7 mg) and 2 (15.8 mg), respectively. Fractions 191 to 229 were subjected to repeated chromatography to obtain 3 (1.7 mg). Fractions 1 to 28 were chromatographed on silica gel column to afford 4 (2.1 mg). The n-BuOH fraction (182 g) was subjected to column chromatography on Diaion HP-20 and eluted with H2O, 10% EtOH, 30% EtOH, 50% EtOH, and 70% EtOH, successively. The fractions eluted with 30% EtOH and 50% EtOH were pooled and subjected to silica gel column chromatography to afford 4 (5.2 mg), 5 (8.4 mg), 6 (12.3 mg), and 7 (4.6 mg). Their chemical structures were identified by spectral analysis using NMR spectrometers and were determined as (–)-sesamin (1) [9, 10], artemitin (2) [11], eupatorin (3) [12], 2,6-dimethoxyquinone (4) [13], eleutheroside B1 (5) [14, 15], luteolin-7-O-D-glucoside (6) [16], and isoorientin (7) [17] by comparing the data with those in the literature. Among them, compounds 4 and 5 were reported for the first time in the genus Achillea; the others (1–3, 6) were all isolated from the species Alpina for the first time. In the original reported papers, due to the limitations of NMR, especially without the help of 2D NMR, some of the 1H and 13C NMR data were misassigned in compound 3. In this paper, all the 1H and 13C NMR spectral data of this compound were reassigned after interpretation of its 2D NMR spectroscopic data. (–)-Sesamin (1). White crystals (petroleum ether–CH3COCH3), mp 121–123 C. UV (MeOH, max, nm): 286, 238. IR (KBr, max, cm –1): 3078, 1500, 1439, 1367, 1250, 1138, 1091, 1029, 922. EI-MS m/z 354 [M]+. 1H NMR (500 MHz, CDCl3, , ppm, J/Hz): 6.85 (2H, d, J = 1.5, H-2, 2 ), 6.80 (2H, dd, J = 8.0, 1.5, H-6, 6 ), 6.78 (2H, d, J = 8.0, H-5, 5 ), 5.95 (4H, s, O-CH2-O), 4.71 (2H, d, J = 4.5, H-7, 7 ), 4.23 (2H, dd, J = 9.0, 7.0, H-9a, 9a ), 3.87 (2H, dd, J = 9.0, 3.5, H-9b, 9b ), 3.05 (2H, m, H-8, 8 ). 13C NMR (125 MHz, CDCl3, , ppm): 148.0 (C-4, 4 ), 147.1 (C-3, 3 ), 135.1 (C-1, 1 ), 119.4 (C-6, 6 ), 108.2 (C-5, 5 ), 106.5 (C-2, 2 ), 101.1 (O-CH2-O), 85.8 (C-7, 7 ), 71.7 (C-9, 9 ), 54.3 (C-8, 8 ). The trans-configuration of H-7 and H-7 was evidenced by their chemical shifts and coupling constants ( 4.71, J = 4.3 Hz), which were observed at 4.42 (J = 7.2 Hz) in the cis-isomers [9].

Conclusion

195Pt, 1H, and 13C NMR spectroscopy was used to study the structure of binuclear platinum(III) acetamidate complexes with 1,10-phenanthroline and 2,2′-bipyridine ligands [Pt2(phen)2(acam)4](NO3)2 (1) and [Pt2(bipy)2(acam)4](NO3)2 (2) in aqueous solutions. The 195Pt NMR spectra of solutions of complexes 1 and 2 in D2O exhibit two signals with satellites due to the 195Pt–195Pt spin-spin coupling (1J(Pt–Pt) ≈ 6345 Hz), whereas their 1H and 13C NMR spectra contain four sets of signals for the protons and the carbon atoms of the heterocyclic and acetamidate ligands. The signals were assigned using the COSY, NOESY, and HSQC/ HMBC experiments and comparing the coordination shifts of the signals for the protons of heterocycles. These data allowed us to draw a conclusion that binuclear complexes 1 and 2 in solution have a head-to-head structure with nonequivalent platinum(III) atoms (coordination cores PtN5 and PtN3O2), the axial-equatorial coordination of the bidentate heterocyclic molecules, and two bridging and two terminal acetamidate ligands.

The enantiomeric purities of disubstituted β‐lactams were determined by 1H and 13C NMR spectroscopy using tris[3‐(trifluoromethylhydroxymethylene)‐d‐camphorato]europium(III), Eu(tfc)3, as a chiral shift reagent. Using a [Eu(tfc)3]/[lactam] ratio of 0.5, most of the resonances were split into signal pairs due to the respective enantiomers. The method gives quantitative enantiomeric compositions. 13C NMR spectroscopy is more advantageous than 1H NMR, which is of limited use owing, for example, to the significant line broadening observed in the 1H spectra at [Eu(tfc)3]/[lactam] &gt; 0.8. Assignments of the proton and carbon signals were obtained for the two enantiomers of the complexed lactams.