bluuebunny/crossref_metadata_2025_split huggingface dataset:
Are Oxazolidinones Really Unproductive, Parasitic Species in Proline Catalysis? – Thoughts and Experiments Pointing to an Alternative View
Authors: Seebach Dieter , Beck Albert K. , Badine D. Michael , Limbach Michael , Eschenmoser Albert , Treasurywala Adi M. , Hobi Reinhard , Prikoszovich Walter , Linder Bernard 
Published: March 2007

AbstractThe N,O‐acetal and N,O‐ketal derivatives (oxazolidinones) formed from proline, and aldehydes or ketones are well‐known today, and they are detectable in reaction mixtures involving proline catalysis, where they have been considered ‘parasitic dead ends’. We disclose results of experiments performed in the early 1970's, and we describe more recent findings about the isolation, characterization, and reactions of the oxazolidinone derived from proline and cyclohexanone. This oxazolidinone reacts (THF, room temperature) with the electrophiles β‐nitrostyrene and chloral (=trichloroacetaldehyde), to give the Michael and aldol adduct, respectively, after aqueous workup (Scheme 5). The reactions occur even at −75° when catalyzed with bases such as 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) or EtN(i‐Pr)2 (DIPEA) (10%; Table 1). It is shown by NMR (Figs. 1 and 3) and IR analysis (Figs. 2 and 4) that the primarily detectable product (before hydrolysis) of the reaction with the nitro‐olefin is again an oxazolidinone. When dissolved in hydroxylic solvents such as MeOH, ‘hexafluoroisopropanol’ ((CF3)2CHOH; HFIP), AcOH, CF3COOH, or in LiBr‐saturated THF, the ring of the oxazolidinone from cyclohexanone and proline opens up to the corresponding iminium ion (Tables 2–4), and when treated with strong bases such as DBU (in (D8)THF) the enamino‐carboxylate derived from proline and cyclohexanone is formed (Scheme 8). Thus, the two hitherto putative participants (iminium ion and enamine) of the catalytic cycle (Scheme 9) have been characterized for the first time. The commonly accepted mechanism of the stereoselective C,C‐ or C,X‐bond‐forming step (i.e., A–D) of this cycle is discussed and challenged by thoughts about an alternative model with a pivotal role of oxazolidinones in the regio‐ and diastereoselective formation of the intermediate enamino acid (by elimination) and in the subsequent reaction with an electrophile (by trans‐addition with lactonization; Schemes 11–14). The stereochemical bias between endo‐ and exo‐space of the bicyclo[3.3.0]octane‐type oxazolidinone structure (Figs. 5 and 6) is considered to possibly be decisive for the stereochemical course of events. Finally, the remarkable consistency, with which the diastereotopic Re‐face of the double bond of pyrrolidino‐enamines (derived from proline) is attacked by electrophiles (Schemes 1 and 15), and the likewise consistent reversal to the Si‐face with bulky (Aryl)2C‐substituents on the pyrrolidine ring (Scheme 16) are discussed by invoking stereoelectronic assistance from the lone pair of pyramidalized enamine N‐atoms.
The Stereostructure of Porphyra‐334: An Experimental and Calculational NMR Investigation. Evidence for an Efficient ‘Proton Sponge’
Authors: Klisch Manfred , Richter Peter , Puchta Ralph , Häder Donat‐P. , Bauer Walter 
Published: March 2007

AbstractThe mycosporine‐like amino acid (MAA) porphyra‐334 (1) is subjected to extensive 1H‐ and 13C‐NMR analysis as well as to density‐functional‐theory (DFT) calculations. All 1H‐ and 13C‐NMR signals of 1 are assigned, as well as the resonances of prochiral proton pairs. This is achieved by 500‐MHz standard COSY, HMQC, and HMBC experiments, as well as by one‐dimensional (DPFGSE‐NOE) and two‐dimensional (NOESY) NOE experiments. Diffusion measurements (DOSY) confirm that 1 is monomeric in D2O solution. DFT Calculations yield 13C‐NMR chemical shifts which are in good agreement for species 6 which is the imino N‐protonated form of 1. An exceptionally high proton affinity of 265.7 kcal/mol is calculated for 1, indicating that 1 may behave as a very powerful ‘proton sponge’ of comparable strength as synthetic systems studied so far. Predictions of 13C‐NMR chemical shifts by the ‘NMRPredict’ software are in agreement with the DFT data. The absolute configuration at the ring stereogenic center of 1 is concluded to be (S) from NOE data as well as from similarities with the absolute configuration (S) found in mycosporine‐glycine 16. This supports the assumption that 1 is biochemically derived from 3,3‐O‐didehydroquinic acid (17). The data obtained question the results recently published by a different research group claiming that the configuration at the imino moiety of 1 is (Z), rather than (E) as established by the here presented study.
5‐Morpholino‐1,2,3,4‐thiatriazole as a Sulfur‐Transfer Reagent in the Reactions with Thioketones
Authors: Mlostoń Grzegorz , Woźnicka Marta , Heimgartner Heinz 
Published: March 2007

AbstractThe thermal decomposition of 5‐morpholino‐1,2,3,4‐thiatriazole (7), which leads to the extrusion of an active form of sulfur, in the presence of different thioketones is described. The interception of the S‐atom by the CS bond leads to in situ formation of an elusive thiocarbonyl S‐sulfide of type 5. This intermediate is a prone 1,3‐dipole, which undergoes effectively [2+3] cycloadditions with thioketones to yield 1,2,4‐trithiolane derivatives in a regioselective manner. Unexpectedly, 3,3‐dichloro‐2,2,4,4‐tetramethyl‐3‐thioxocyclobutanone (1c) does not lead to the expected symmetrical 1,2,4‐trithiolane. This result can be explained by the reduced stability of the corresponding thiosulfine 5c. Three‐component reactions, which were carried out in the presence of equimolar amounts of two different thioketones, result in the formation of ‘mixed’ 1,2,4‐trithiolanes of type 8.
At‐a‐station hydraulic geometry relations, 1: theoretical development
Authors: Singh Vijay P. , Zhang L. 
Published: March 2007

AbstractThis paper, the first of two, hypothesizes that: (1) the temporal variation of stream power of a river channel at a given station with varying discharge is accomplished by the temporal variation in channel form (flow depth and channel width) and hydraulic variables, including energy slope, flow velocity and friction; (2) the change in stream power is distributed among the changes in flow depth, channel width, flow velocity, slope, and friction, depending on the boundary conditions that the channels has to satisfy. The second hypothesis is a result of the principle of maximum entropy and the theory of minimum energy dissipation or its simplified minimum stream power. These two hypotheses lead to families of at‐a‐station hydraulic geometry relations. The conditions under which these families of relations can occur in the field are discussed. Copyright © 2007 John Wiley & Sons, Ltd.
Investigating hydrologic connectivity and its association with threshold change in runoff response in a temperate forested watershed
Authors: James April L. , Roulet Nigel T. 
Published: March 2007

AbstractHydrological studies across varied climatic and physiographic regions have observed small changes in the ‘states of wetness’; based on average soil moisture, can lead to dramatic changes in the amount of water delivered to the stream channel. This non‐linear behaviour of the storm response has been attributed to a critical switching in spatial organization of shallow soil moisture and hydrologic connectivity. However, much of the analysis of the role of soil moisture organization and connectivity has been performed in small rangeland catchments. Therefore, we examined the relationship between hydrologic connectivity and runoff response within a temperate forested watershed of moderate relief. We have undertaken spatial surveys of shallow soil moisture over a sequence of storms with varying antecedent moisture conditions. We analyse each survey for evidence of hydrologic connectivity and we monitor the storm response from the catchment outlet. Our results show evidence of a non‐linear response in runoff generation over small changes in measures of antecedent moisture conditions; yet, unlike the previous studies of rangeland catchments, in this forested landscape we do not observe a significant change in geostatistical hydrologic connectivity with variations in antecedent moisture conditions. These results suggest that a priori spatial patterns in shallow soil moisture in forested terrains may not always be a good predictor of critical hydrologic connectivity that leads to threshold change in runoff generation, as has been the case in rangeland catchments. Copyright © 2007 John Wiley & Sons, Ltd.
C620R mutation of the murine ret proto‐oncogene: Loss of function effect in homozygotes and possible gain of function effect in heterozygotes
Authors: Yin Luo , Puliti Aldamaria , Bonora Elena , Evangelisti Cecilia , Conti Valerio , Tong Wei‐Min , Medard Jean‐Jacques , Lavoué Marie‐France , Forey Nathalie , Wang Lily C. , Manié Serge , Morel Gérard , Raccurt Mireille , Wang Zhao‐Qi , Romeo Giovanni 
Published: March 2007

AbstractGermline RET mutations are responsible for different inherited disorders: Hirschsprung disease (congenital aganglionic megacolon), caused by loss of function mutations, familial medullary thyroid carcinoma and multiple endocrine neoplasia type 2, caused by gain of function mutations. Intriguingly, some RET mutations, including C620R, are associated with both types of diseases. To investigate the dual role of such RET mutations, a mouse model with a targeted mutation retC620R was generated. retC620R/C620R offspring die during the first postnatal day, and show kidney agenesis and intestinal aganglionosis. Decreased outgrowth of the Ret‐positive cells was observed in retC620R/C620R neuronal cell cultures, which is suggestive of an impaired migration, proliferation or survival of the Ret‐expressing cells. Electronmicroscopy revealed the absence of membrane‐bound Ret in retC620R/C620R cells as compared to ret+/+ and ret+/C620R cells. On the other hand, aged ret+/C620R mice develop precancerous lesions in the adrenal gland or in the thyroid. Our results suggest that the retC620R mutation has a loss of function effect in homozygotes and exhibits a dominant gain of function effect with low penetrance causing hyperplasia in heterozygotes. © 2007 Wiley‐Liss, Inc.
Absence of measles virus genome and transcripts in Hodgkin‐Reed/Sternberg cells of a cohort of Hodgkin lymphoma patients
Authors: Maggio Ewerton , Benharroch Daniel , Gopas Jacob , Dittmer Ulf , Hansmann Martin‐Leo , Küppers Ralf 
Published: March 2007

AbstractIn the search for viruses in Hodgkin lymphoma (HL), it was reported that the measles virus (MV) can be detected in the Hodgkin‐Reed/Sternberg (HRS) cells of a large fraction of cases from Israel by immunohistochemistry or in situ hybridisation, suggesting a potential role of this virus in HL. To extend and validate this report, we studied HL‐derived cell lines and HRS cells microdissected from German and Israeli HL cases for the presence of MV RNA genome and transcripts, analysing three MV genes (nucleoprotein, matrix, haemaglutinin). A cell line infected with MV was used as a positive control for MV RNA detection. MV RNA was detectable down to 1 infected cell in a nested RT‐PCR. Pools of microdissected HRS cells from 18 German and 7 Israeli classical HL (the latter reported to be positive for MV proteins in the previous study) were analysed for MV genome and transcripts. None of the viral genes was obtained in independent replicate experiments in any of the 25 HL cases. A Southern blot hybridisation performed with the second round PCR products further confirmed the negative results. Whole HL tissue sections were analysed to exclude MV in non‐HRS cells, also yielding negative results. We also analysed four HL cell lines and showed that these are MV‐negative, too. In this cohort of German and Israeli HL patients—including cases previously typed as MV‐positive—and HL‐derived cell lines, there was no evidence of MV genome in the HRS cells. © 2007 Wiley‐Liss, Inc.
Medical radiation exposure and breast cancer risk: Findings from the Breast Cancer Family Registry
Authors: John Esther M. , Phipps Amanda I. , Knight Julia A. , Milne Roger L. , Dite Gillian S. , Hopper John L. , Andrulis Irene L. , Southey Melissa , Giles Graham G. , West Dee W. , Whittemore Alice S. 
Published: March 2007

AbstractModerate to high‐dose radiotherapy is known to increase the risk of breast cancer. Uncertainties remain about the effects of low‐dose chest X‐rays, particularly in individuals at increased genetic risk. We analyzed case‐control data from the Breast Cancer Family Registry. Self‐reported data on therapeutic and diagnostic radiation exposures to the chest were available for 2,254 breast cancer cases and 3,431 controls (1,556 unaffected sisters and 1,875 unrelated population controls). We used unconditional logistic regression analyses to estimate odds ratios (OR) and 95% confidence intervals (CI) associated with radiation exposure, after adjusting for age, study center, country of birth, and education. Increased risks for breast cancer were found for women who had radiotherapy for a previous cancer (OR = 3.55, CI = 1.47–8.54) and diagnostic chest X‐rays for tuberculosis (OR = 2.49, CI = 1.82–3.40) or pneumonia (OR = 2.19, CI = 1.38–3.47). Risks were highest for women with a large number of exposures at a young age or exposed in earlier calendar years. There was no evidence of increased risk associated with other diagnostic chest X‐rays (not including tuberculosis or pneumonia), both in women with and without indicators of increased genetic risk (i.e., diagnosed at age <40 years or family history of breast cancer). Given the widespread and increasing use of medical diagnostic radiation, continued surveillance of breast cancer risk is warranted, particularly in women at specific genetic risk, such as those carrying mutations in BRCA1 or BRCA2. © 2007 Wiley‐Liss, Inc.
Cutaneous malignant melanoma in children and adolescents in Sweden, 1993–2002: The increasing trend is broken
Authors: Karlsson Pia M. , Fredrikson Mats 
Published: March 2007

AbstractThe incidence of cutaneous malignant melanoma rose rapidly in teenagers in Sweden during 1973–1992, while it remained low in younger children. To study the further trends and characteristics of melanoma in this young population, data on all cases in individuals under 20 years of age reported to the Swedish Cancer Registry during 1993–2002, and the corresponding pathology reports were examined. Seventy‐nine cases were reported to the Registry. There were 24 males and 55 females. Most melanomas occurred on the trunk followed by the legs in both genders. The median tumor thickness was 0.8 mm. Children under age 15 had thicker melanomas than individuals aged 15–19. Superficial spreading melanoma was the most common histological subtype (43/78, 55%). The melanoma‐specific 5‐year survival rate was 90%. During 1993–2002, the age‐standardized incidence fell to 3.6/million from 5.0/million in 1983–1992 (RR 0.74, 95% CI 0.58–0.92). The most pronounced decrease was for melanomas on the trunk in boys and on the legs in girls. The incidence for 15–19‐year‐old boys peaked for the cohort born between 1968 and 1972 and for girls between 1973 and 1977. The decrease in incidence may be a result of public health campaigns aiming at reducing sun exposure in childhood. A contributing effect from an increased immigration of individuals with darker complexions and at a lower melanoma risk is probable. © 2007 Wiley‐Liss, Inc.
Serum C‐peptide, IGFBP‐1 and IGFBP‐2 and risk of colon and rectal cancers in the European Prospective Investigation into Cancer and Nutrition
Authors: Jenab Mazda , Riboli Elio , Cleveland Rebecca J. , Norat Teresa , Rinaldi Sabina , Nieters Alexandra , Biessy Carine , Tjønneland Ann , Olsen Anja , Overvad Kim , Grønbæk Henning , Clavel‐Chapelon Françoise , Boutron‐Ruault Marie‐Christine , Linseisen Jakob , Boeing Heiner , Pischon Tobias , Trichopoulos Dimitrios , Oikonomou Eleni , Trichopoulou Antonia , Panico Salvatore , Vineis Paolo , Berrino Franco , Tumino Rosario , Masala Giovanna , Peters Petra H. , van Gils Carla H. , Bueno‐de‐Mesquita H. Bas , Ocké Marga C. , Lund Eiliv , Mendez Michelle A. , Tormo María José , Barricarte Aurelio , Martínez‐García Carmen , Dorronsoro Miren , Quirós José Ramón , Hallmans Göran , Palmqvist Richard , Berglund Göran , Manjer Jonas , Key Timothy , Allen Naomi E. , Bingham Sheila , Khaw Kay‐Tee , Cust Anne , Kaaks Rudolf 
Published: March 2007

AbstractWestern style diets and lifestyles are associated with increasing rates of obesity, diabetes and insulin resistance. Higher circulating insulin levels may modulate cell proliferation and apoptosis either directly or indirectly by increasing the bioactivity of IGF‐I and decreasing the bioactivity of some of its binding proteins. The objective of this study was to determine the association of increasing levels of serum C‐peptide, a biomarker of pancreatic insulin secretion, and IGF binding proteins (IGFBP) ‐1 and ‐2 with colorectal cancer risk in a case–control study nested within the European Prospective Investigation into Cancer and Nutrition (EPIC), a large cohort involving 10 Western European countries. A total of 1,078 colorectal cancer cases were matched (age, date of blood donation, fasting status, gender, study center) to an equal number of control subjects. Relative cancer risks were estimated using conditional logistic regression models. Serum C‐peptide concentration was positively associated with an increased colorectal cancer risk for the highest versus the lowest quintile (OR = 1.56, 95% CI = 1.16–2.09, ptrend < 0.01), which was slightly attenuated after adjustment for BMI and physical activity (OR = 1.37, 95% CI = 1.00–1.88, ptrend = 0.10). When stratified by anatomical site, the cancer risk was stronger in the colon (OR = 1.67, 95% CI = 1.14–2.46, ptrend < 0.01) than in the rectum (OR = 1.42, 95% CI = 0.90–2.25, ptrend = 0.35). The cancer risk estimates were not heterogeneous by gender or fasting status. No clear colorectal cancer risk associations were observed for IGFBP‐1 or ‐2. This large prospective study confirms that hyperinsulinemia, as determined by C‐peptide levels, is associated with an increased colorectal cancer risk. © 2007 Wiley‐Liss, Inc.
New paths to dramatically improve your planning and control processes
Authors: Player Steve 
Published: March 2007

AbstractThe Beyond Budgeting framework is a new approach for organizational planning and control. Depending on the people and the culture, an organization can take either a revolutionary or an evolutionary approach to implementation. Three common traits required by a move to continuous planning and adaptive controls are: (1) a degree of enlightened leadership that allows innovation; (2) commitment to change culture and behaviors as well as processes; and (3) utilization of fast, open information systems. The organizations taking these approaches are better prepared to create lean, ethical, and adaptive organizations. © 2007 Wiley Periodicals, Inc.
Reversal of BCRP‐mediated multidrug resistance by stable expression of small interfering RNAs
Authors: Lv Hui , He Zhimin , Liu Xiaorong , Yuan Jianhui , Yu Yanhui , Chen Zhuchu 
Published: March 2007

AbstractBreast cancer resistance protein (BCRP) is an ATP‐binding cassette multidrug transporter that confers resistance to various anticancer drugs like Mitoxantrone. Overexpression of BCRP confers multidrug resistance (MDR) in cancer cells and is a frequent impediment to successful chemotherapy. For stable reversal of BCRP‐depending MDR by RNA interference technology, a hU6‐RNA gene promoter‐driven expression vector encoding anti‐BCRP short hairpin RNA (shRNA) molecules was constructed. By treating endogenously and exogenously expresses high levels of BCRP cells with these constructs, expression of the targeted BCRP‐encoding mRNA, and transport protein was inhibited completely. Furthermore, the accumulation of mitoxantrone in the anti‐BCRP shRNA‐treated cells increased. And the sensitivity to mitoxantrone of anti‐BCRP shRNA‐treated cells is increased 14.6‐fold and 2.44‐fold respectively compared to their control (P < 0.05). These data indicated that stable shRNA‐mediated RNAi could be tremendously effective in reversing BCRP‐mediated MDR and showed promises in overcoming MDR by gene therapeutic applications. J. Cell. Biochem. 102: 75–81, 2007. © 2007 Wiley‐Liss, Inc.
Influence of fatty acid composition on the tribological performance of two vegetable‐based lubricants
Authors: Siniawski Matthew T. , Saniei Nader , Adhikari Bigyan , Doezema Lambert A. 
Published: March 2007

AbstractIn light of diminishing natural resources, global climatic change and increased environmental sensitivity, renewable‐based lubricants are being considered potential alternatives to petroleum‐based lubricants. Understanding the tribological performance of vegetable‐based lubricants in relation to their chemical composition is essential for their industrial implementation. This study focuses on the friction and abrasion rate characteristics of soybean and sunflower oils in comparison to a base mineral oil under sliding wear at ambient conditions for various applied loads. It was found that the abrasion rate and friction were the least severe for the soybean, followed by the sunflower oil. The observed trends were attributed to differences in their fatty acid compositions, in particular, a lower percentage of linoleic and oleic acids within the soybean oil. Copyright © 2007 John Wiley & Sons, Ltd.
Isolation and structural determination of sorbinols A and B, new triterpenes from Sorbus cashmariana, by 1D and 2D NMR spectroscopy
Authors: Kazmi Mehdi Hassan , Ahmed Ejaz , Hameed Saira , Malik Abdul , Ashraf Muhammad 
Published: March 2007

AbstractTwo new pentacyclic triterpenes, sorbinols A (1) and B (2) have been isolated from the ethyl acetate fraction of Sorbus cashmariana and their structures assigned from 1H and 13C NMR spectra, DEPT and by 2D COSY, NOE, HMQC and HMBC experiments. Both 1 and 2 showed moderate inhibitory potential against the enzyme lipoxygenase. Copyright © 2007 John Wiley & Sons, Ltd.
Synthesis and spectroscopic characterisation of a combinatorial library based on the fungal natural product 3‐chloro‐4‐hydroxyphenylacetamide
Authors: Davis Rohan A. , Pierens Gregory K. , Parsons Peter G. 
Published: March 2007

AbstractParallel solution‐phase chemistry has yielded a series of secondary amide analogues of the fungal natural product 3‐chloro‐4‐hydroxyphenylacetamide. 3‐Chloro‐4‐hydroxyphenylacetic acid was coupled to a variety of primary amines using 1‐ethyl‐3‐(3′‐dimethylamino‐ propyl)‐carbodiimide hydrochloride. The desired products were obtained in good yield and high purity following rapid silica purification. All analogues were spectroscopically characterised using NMR, UV, IR and MS data. One compound displayed moderate cytotoxicity against the human melanoma and prostate cell lines, MM96L and DU145. Copyright © 2007 John Wiley & Sons, Ltd.
Differences in perceived barriers to volunteering to formal organizations: Lack of time versus lack of interest
Authors: Sundeen Richard A. , Raskoff Sally A. , Garcia M. Cristina 
Published: March 2007

AbstractThis article reports the findings of a study of perceived barriers to volunteering to formal organizations by nonvolunteers. We examine the types of barriers, their frequencies, and their relationships with individual‐level sociodemographic characteristics of nonvolunteers. Data from a 2001–2002 national survey conducted by the U.S. Bureau of Labor Statistics are analyzed using multiple regression techniques. Contrary to general expectations, only three barriers—lack of time, lack of interest, and ill health—are fairly common. Furthermore, as expected, different social class groups identify different types of barriers. The article concludes with a discussion of the theoretical implications of the findings (for example, how indicators of social and cultural capital affect access to volunteer opportunities) and practical implications concerning recruitment of volunteers.