Discrimination of stereoisomers by one-dimensional 13 C NMR: All 16 stereoisomers of 4-hydroxy-α-tocopherol resolved.

All 16 resolved! A vitamin E-derived compound containing four chiral centers is the first example where all stereoisomers, that is, eight diastereomeric pairs of enantiomers, could be discriminated in a single NMR run. Measurement at 176 MHz in the presence of Pirkle's alcohol as a chiral solvating agent is a relatively robust, simple, easy-to-set-up, and fast method.

The Crystalline Sponge Method in Water.

The crystalline sponge method entails the elucidation of the (absolute) structure of molecules from a solution phase using single-crystal X-ray diffraction and eliminates the need for crystals of the target compound. An important limitation for the application of the crystalline sponge method is the instability of the available crystalline sponges that can act as host crystals. The host crystal that is most often used decomposes in protic or nucleophilic solvents, or when guest molecules with Lewis basic substituents are introduced. Here a new class of (water) stable host crystals based on f-block metals is disclosed. It can be shown that these hosts not only increase the scope of the crystalline sponge method to a wider array of solvents and guests, but that they can even be applied to aqueous solutions containing hydrophilic guest molecules, thereby extending the crystalline sponge method to the important field of water-based chemistry.

One-Dimensional 13C NMR Is a Simple and Highly Quantitative Method for Enantiodiscrimination.

The discrimination of enantiomers of mandelonitrile by means of 1D 13C NMR and with the aid of the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol (TFAE) is presented. ¹H NMR fails for this specific compound because proton signals either overlap with the signals of the chiral solvating agent or do not show separation between the (S)-enantiomer and the (R)-enantiomer. The 13C NMR method is validated by preparing artificial mixtures of the (R)-enantiomer and the racemate, and it is shown that with only 4 mg of mandelonitrile a detection limit of the minor enantiomer of 0.5% is obtained, corresponding to an enantiomeric excess value of 99%. Furthermore, the method shows high linearity, and has a small relative standard deviation of only 0.3% for the minor enantiomer when the relative abundance of this enantiomer is 20%. Therefore, the 13C NMR method is highly suitable for quantitative enantiodiscrimination. It is discussed that 13C NMR is preferred over ¹H NMR in many situations, not only in molecules with more than one chiral center, resulting in complex mixtures of many stereoisomers, but also in the case of molecules with overlapping multiplets in the ¹H NMR spectrum, and in the case of molecules with many quaternary carbon atoms, and therefore less abundant protons.

A Simple ¹³C NMR Method for the Discrimination of Complex Mixtures of Stereoisomers: All Eight Stereoisomers of α-Tocopherol Resolved.

A simple one-dimensional (13)C NMR method is presented to discriminate between stereoisomers of organic compounds with more than one chiral center. By means of this method it is possible to discriminate between all eight stereoisomers of α-tocopherol. To achieve this the chiral solvating agent (S)-(+)-1-(9-anthryl)-2,2,2-trifluoroethanol and the compound of interest were dissolved in high concentrations in chloroform-d, and the nuclear magnetic resonance (NMR) spectrum was recorded at a low temperature. The individual stereoisomers of α-tocopherol were assigned by spikes of the reference compounds. The method was also applied to six other representative examples.

Flow injection analysis electrospray ionization mass spectrometry for high-throughput screening of a gene library for amidase activity.

In high-throughput screening of gene and mutant libraries, high analysis speeds and short method development times are important factors. Mass spectrometry (MS) is considered to be a generic analytical technique with a relatively short development time. Furthermore, when applying flow injection analysis (FIA) for sample introduction, the requirements for high throughput are met. In this work, the use of a single quadrupole electrospray MS instrument for assaying amidase activity in a gene library is demonstrated. The desired selectivity for measuring the amino acid, the reaction product of the amidase reaction, in the presence of high concentrations of the corresponding amino acid amide substrate was obtained by selective ionization of the amino acid in negative ion mode electrospray. The only sample preparation required was a 200-fold dilution of the reaction mixture. For obtaining quantitative results, a complementary calibration procedure was set up to correct for the change in ionization suppression as a function of conversion. This approach was used to screen a Mycobacterium neoaurum gene library consisting of 11,520 clones with alpha-methylleucine amide as substrate within 24h. Conversion was measured on the [M-H]- species of the corresponding alpha-methylleucine (m/z 144). Five positive clones were detected with a conversion ranging from 0.2% to 3.4%.

Ultra-performance liquid chromatographic analysis of amino acids in protein hydrolysates using an automated pre-column derivatisation method.

In the present study, the changeover from the Pico.Tag HPLC method to the AccQ.Tag(ultra) UPLC method for the analysis of amino acids in casein and bovine serum albumine hydrolysates is described. The total chromatographic run time of the AccQ.Tag(ultra) UPLC method was only 40% of the time required for the Pico.Tag HPLC method. Quantitative results of both methods for casein and bovine serum albumine hydrolysates compared fairly well. The derivatisation protocol for the formation of AQC derivatives of amino acids was automated using a Gilson Model 215 liquid handler. Comparison of the manual derivatisation protocol with the automated protocol showed lower coefficients of variation for the latter. Combination of the AccQ.Tag(ultra) UPLC method and automated derivatisation resulted in improved throughput compared to the Pico.Tag HPLC method.

Enantioselective gas chromatographic analysis of aqueous samples by on-line derivatisation. Application to enzymatic reactions.

A new gas chromatography (GC) method is presented for analysing both the conversion and the enantiomeric excess (e.e.) of samples from alcohol dehydrogenase reactions. The chiral compounds studied were a series of saturated, straight chain alcohols, ranging from 2-butanol to 2-heptanol. The alcohols were converted to the corresponding trifluoroacetylated derivatives by injecting trifluoroacetic anhydride onto the column shortly after injection of the aqueous samples in split-injection mode (1:100) onto a Chiraldex G-TA capillary GC column. Injecting seven hundred aqueous enzymatic reaction mixtures according to the above-mentioned procedure revealed no noticeable loss of column performance. Using the new GC method, conventional sample work-up procedures such as extraction and off-line derivatisation are eliminated and throughput of samples is significantly enhanced.

Racemic and Enantiopure Camphene and Pinene Studied by the Crystalline Sponge Method.

The use of an achiral metal-organic framework for structure determination of chiral compounds is demonstrated for camphene and pinene. The structure of enantiopure ß-pinene can be resolved using the crystalline sponge method. However, α-pinene cannot be resolved using enantiopure material alone because no ordering of guest molecules takes place in that case. Interestingly, enantiomeric pairs order inside the channels of the host framework when impure (+)-camphene is offered to the host, which is also the case when a racemic mixture of α-pinene is used. A mixture of (+)-α-pinene and (-)-ß-pinene also leads to ordered incorporation in the host, showing the influence of the presence of an inversion center in the host framework. We further show that powder X-ray diffraction provides a direct view on incorporation of ordered guest molecules. This technique, therefore, provides a way to determine the optimal and/or minimal soaking time. In contrast, color change of the crystal only demonstrates guest uptake, not ordering. Moreover, we show that color change can also be caused by guest-induced host degradation.

Selective and sensitive determination of lactose in low-lactose dairy products with HPAEC-PAD.

The demand for low lactose dairy products is increasing and more different lactose free food is commercially available. The level of lactose in these products decreased during the last years and nowadays a concentration of <0.01% is generally accepted as "lactose free". For the determination of the lactose concentrations in these dairy products a sensitive analysis method is needed. We developed a method for the determination of low concentrations of lactose in a wide range of dairy products. A simple sample preparation with dilution, centrifugation and ultrafiltration is efficient for the isolation of lactose from the sample matrix. In this paper, a new HPAEC-PAD analysis on a CarboPac PA100 column gives a good separation of lactose from the other saccharides. This separation in combination with the PAD detector yields a selective and sensitive method for the quantification at the desired concentrations of lactose in low lactose dairy products.

Familial achalasia of the esophagus in mother and son: a possible pathogenetic relationship.

Familial achalasia most often has been recorded in siblings, and only rarely (twice previously) in a parent and offspring. This report concerns a third case of achalasia in a parent and offspring (mother and son). Clinical and radiographic features of the esophageal achalasia are presented. The possibility that genetic factors may play a role in the etiology of this disorder is discussed.

Application of monodentate secondary phosphine oxides, a new class of chiral ligands, in Ir(i)-catalyzed asymmetric imine hydrogenation.

Secondary phosphine oxides were prepared from R(1)PCl(2) and R(2)MgBr, followed by hydrolysis. They were obtained in an enantiopure form by preparative chiral HPLC. These new monodentate ligands were tested in the iridium-catalyzed hydrogenation of imines at 25 bar. Enantioselectivities up to 76% were obtained at L/Ir = 2. Addition of pyridine (Pyr/Ir = 1:2) raised the ee to 83%. Using pyridine as an additive allowed reduction of the L/Ir ratio to 1 without reduction of ee. [reaction: see text]

Chiral liquid chromatography-mass spectrometry for high-throughput screening of enzymatic racemase activity.

In finding suitable biocatalysts for processes in chemical industry, expression libraries are constructed containing typically >10,000 clones. Search for a desired activity is done by examination of all the clones in one or more libraries using a high-throughput screening assay. Here we describe a method for the screening of the enzymatic racemase activity of clones from an expression library on alpha-amino-epsilon-caprolactam (ACL) using a fast chiral LC separation and ionspray-MS as the detection technique. After substrate incubation with S-ACL, the 96-well microplates were centrifuged to remove cell material. The conversion of S-ACL to R-ACL was monitored by quantitation of the R-ACL enantiomer. Separation of the two ACL enantiomers was performed on a Crownpak CR+ column within 1 min. A Gilson 215 autosampler with a 889 multiple injection probe was used for injecting the samples into the LC system. The total analysis time for a 96-well microplate was 56 min. The MS was operated in the positive-ion mode using selected ion monitoring at m/z 129 [M+H]+ of ACL. Using this method over 12,000 samples were analyzed without loss in performance of the system. The LC column remained stable without loss of resolution and the MS system did not show loss in sensitivity throughout the screening. Inter-day reproducibility was within 15%.

Cure rates in small cell and non-small cell carcinoma of the lung utilizing high-dose radiotherapy and chemotherapy.

From 1967 to 1977, 72 patients with small cell carcinoma of the lung were seen. Thirty-five of these patients had unilaterally localized lesions (limited disease) and were treated with cobalt 60 radiation therapy (6,000 rad in six weeks) followed by chemotherapy consisting of cyclophosphamide (Cytoxan), vincristine, methotrexate and lomustine (CCNU) (Group A). The remaining 37 patients with extensive disease were treated with similar chemotherapy alone, or in combination with local palliative radiotherapy to the symptomatic area (Group B). For Group A the five-year survival rate was 20 percent, while for both groups combined, it was only 5 percent.During this same period 560 patients with non-small cell carcinomas were treated. The five-year survival rate for those patients with operable, resectable lesions was 33 percent, while for those with unilateral, inoperable, unresectable lesions, it was 10 percent. Thus, it would appear that the results in limited small cell and non-small cell carcinomas of the lung utilizing high-dose radiotherapy followed by chemotherapy are comparable, and that limited small cell carcinoma of the lung patients with high-dose radiotherapy followed by chemotherapy can survive longer than those patients with stage III, non-small cell lung carcinoma.While the two- to five-year survival rates in small cell carcinoma demonstrate no appreciable differences, in non-small cell carcinomas there are significant two- to five-year survival differences. These improved results probably are due to the increased sensitivity of small cell carcinoma to high-dose local radiotherapy and to the chemotherapeutic vulnerability of circulating and microscopic metastatic cancer cells.

Why quality assurance?

Quality assurance programs in radiology are essential and each radiologist must be committed to exert comprehensive efforts toward excellent quality control. Identification and evaluation of a radiological problem, corrective action, and good record keeping are essential features of a well-managed quality assurance program. This paper discusses the background and impact of these programs on providing safe radiologic services to patients.

Osteosarcoma of the maxilla treated with radiation therapy and surgery.

Osteosarcoma (osteogenic sarcoma) presumably arises from mesenchyme and is characterized by the production of malignant osteoid by the sarcomatous stroma. When all cases are considered, osteosarcoma occurs more frequently in the younger age group (peak range of 10 to 25 years of age) and commonly involves extremity bones, particularly the lower. Osteogenic sarcoma rarely arises in the maxilla. The usual treatment is radical maxillectomy, postoperative radiation therapy, and chemotherapy. Results usually are very poor.A case is presented of a 33-year-old man in whom a diagnosis of osteogenic sarcoma of the maxilla was made eight years previously. The treatment was unusual. Preoperative radiation therapy was accomplished by drilling holes in the tumor and adjacent maxilla into which were implanted high-dose radium needles. This was followed by a left radical maxillectomy. The patient is cured and is without functional deficiencies up to the present time.

Acupuncture in the People's Republic of China.

Recent worldwide interest in acupuncture has been manifested. Although the rationale for its efficacy as an anesthetic agent is unknown, 25 to 35 percent of surgery in the People's Republic of China is performed under acupuncture anesthesia. The authors discuss the indications, advantages and disadvantages, and complications of acupuncture anesthesia and comment on current theories of the mechanism of its action.

Renal angiomyolipoma with retroperitoneal adenopathy.

To date, only two cases of renal angiomyolipoma with associated lymph node involvement have been described. The authors report a third instance of this unusual entity.

Intrathoracic thyroid.

A case of intrathoracic or substernal thyroid is presented. The anatomical and radiological features and differential diagnoses are discussed.

Epidermoid carcinoma subsequent to a gunshot wound of the face.

Reported is a case of epidermoid carcinoma of the face following a gunshot wound. A review of the pertinent literature is included.

Hamartoma.

The case of a patient with benign pulmonary hamartoma is presented. Examination of the lung by roentgenographic rays demonstrated the classical "popcorn calcification" in the lesion.