bluuebunny/crossref_metadata_2025_split huggingface dataset:
Methylenetetrahydrofolate reductase gene A222V polymorphism and risk of ischemic stroke
Authors: Baum Larry , Wong Ka Sing , Ng Ho Keung , Tomlinson Brian , Rainer Timothy Hudson , Chan Daniel Kam Yin , Thomas G. Neil , Chen Xiangyan , Poon Peter , Cheung Wing Sze , Woo Kam Sang 
Published: November 2004

AbstractThe 5,10-methylenetetrahydrofolate reductase (
The assessment of bone metabolism in female elite endurance athletes by biochemical bone markers
Authors: Herrmann Markus , Herrmann Wolfgang 
Published: November 2004

AbstractPurpose: Premature osteoporosis is a frequent problem in female athletes. Current concepts suggest that a disruption of the hypothalamic-pituitary axis leads to hypoestrogenism, which then causes amenorrhea and osteoporosis. However, the underlying mechanisms have been insufficiently investigated. Osteoprotegerin (OPG) and soluble TNF-α receptor antagonist ligand (sRANKL) regulate the balance of osteoblasts and osteoclasts. Their role in the pathogenesis of osteoporosis in female athletes has not been studied yet.Methods: We measured OPG and sRANKL in relation to biochemical bone markers [osteocalcin (OC), bone alkaline phosphatase (BAP), serum β-crosslaps (CTx)] and female sex hormones [estradiol (E2) and luteinizing hormone (LH)] in fastening blood samples from 25 female elite endurance athletes and 25 matched controls.Results: Athletes exhibited significantly higher levels of the bone resorption marker CTx than controls (0.61±0.26 vs. 0.44±0.15ng/ml). OPG and sRANKL were not changed. Subgroup analysis revealed that athletes using oral contraceptives [A-OCC(−)] had significantly higher levels of CTx (0.82±0.20 vs. 0.50±0.14ng/ml), BAP [37.3 (23.2–54.4) U/l vs. 25.2 (20.3–35.6) U/l] and OPG (3.4±0.8 vs. 2.7±0.8ng/ml) than controls who did not use oral contraceptives [C-OCC(−)]. While the difference for CTx exceeded the least significant change in this marker by approximately 30%, the differences for the bone formation markers OC and BAP were close to the least significant change. In athletes using oral contraceptives [A-OCC(+)] we found no differences compared to controls.Conclusions: A-OCC(−) athletes have increased bone turnover with a particular stimulation of bone resorption. The increased bone resorption is not accompanied by a shift of the OPG/sRANKL relationship towards an osteoclastogenic constellation. Since increased bone resorption was not detectable in A-OCC(+) athletes, it can be suggested that OCC use might protect bone health in female athletes.
Production of gender-specific morning salivary cortisol reference intervals using internationally accepted procedures
Authors: Patel Rajan S. , Shaw Steve R. , MacIntyre Halena , McGarry Gerald W. , Michael Wallace A. 
Published: November 2004

AbstractBackground: Salivary cortisol concentrations correlate well with biologically active unbound free plasma cortisol concentrations. Despite its practical and analytical advantages, salivary cortisol measurement has been used mainly as a research tool rather than for the routine evaluation of adrenal function. This may be partly explained by the lack of robust reference data in the literature.Methods: Using the recommended procedures for the production of reference intervals published by the International Federation of Clinical Chemistry, we aimed to produce morning salivary cortisol reference intervals for males and females. Salivary cortisol was measured in 496 specimens collected from 248 reference individuals (128 males, median age 41years, range 16–86; and 120 females, median age 44years, range 16–98) attending an otorhinolaryngology clinic. Reference individuals mailed saliva specimens sampled on two consecutive mornings to our laboratory, where cortisol concentrations were measured.Results: Statistical analysis showed no significant correlation with age or body mass index. The following 95% gender-partitioned reference intervals were produced: males 10.9–40.3nmol/l; and females 9.3–40.3nmol/l.Conclusion: Knowledge of these salivary cortisol reference intervals helps us monitor the adrenal function of outpatients using topical intranasal glucocorticoids for rhinosinusitis.
Concentrations of N-terminal pro-brain natriuretic peptide and troponin T in plasma of 75-year-old apparently healthy persons
Authors: Huber Klaus Roland , Mostafaie Nazanin , Bauer Kurt , Worofka Brigitte , Kittl Eva , Hofmann Jörg , Hejtman Milos , Redei Karoly , Jungwirth Susanne , Fischer Peter , Tragl Karl-Heinz 
Published: November 2004

AbstractClinical chemical reference values for older persons are sparse and mostly intermixed with those for younger persons. We had a unique opportunity to obtain blood samples from volunteers who were 75years old and living in two districts of Vienna, Austria. Consequently, we utilized stored plasma samples to obtain reference intervals for 120 apparently healthy 75-year-old participants for pro-brain natriuretic peptide (proBNP), as well as for troponin T. The N-terminal (NT)-proBNP protein assay is currently used as a diagnostic and prognostic aid in patients with heart failure and as a prognostic marker in acute coronary syndromes. Specifically, the concentration of NT-proBNP in serum or plasma aids in the prognosis of ventricular systolic dysfunction and helps to differentiate between cardiac and non-cardiac causes. The median NT-proBNP plasma value for men and women in our cohort was calculated as 98pg/ml, comparing favorably with reported values, in that a NT-proBNP concentration less than 100pg/ml excludes acutely decompensated heart failure. Our calculated 97.5 percentile was slightly higher (359 pg/ml) than the 97.5 percentile in a group of 50–65-year-old persons (198 and 222pg/ml for men and women, respectively) revealing the influence of age on this parameter. Because of its high tissue-specificity, cardiac troponin T is a cardiospecific, highly sensitive marker for myocardial damage. However, the troponin T concentrations in the plasma specimens from this cohort were all below the detection limit of 0.01ng/ml, preventing any further data handling.
Pace and Lead: The Grammar of Rapport
Authors: Bronson Matthew C. 
Published: November 2004

Neurlolinguistic programming is a powerful technology for modelling aspects of human excellence so that others can achieve similar levels of effectiveness. This article describes how to teach a simple communication pattern called "pace and lead,” derived from studies of the hypnotic induction techniques of such master hypnotists as Milton Erickson. The "Pace and Lead" frame consists of several sensorily verifiable statements (pace) followed by a positive suggestion (lead). This pattern is the basis for virtually all communication which seeks to influence, manipulate or heal and as such, constitutes a very useful skill with a wide variety of applications.This frame—simple in its outward form but profound in its potential extension to a variety of real world situations—deserves more general inclusion in the teaching of consciousness curriculum. Anthropologists with an interest in language and consciousness issues will appreciate the accessibility of the exercise and its ability to concretely embody abstract issues such as the role of language in the creation of personal and cultural "realities.”
The Catalyzed NucleophilicAddition of Aldehydes to Electrophilic Double Bonds
Authors: Stetter Hermann , Kuhlmann Heinrich 
Published: November 2004

AbstractThe cyanide‐ion‐catalyzed dimerization of aromatic and heterocyclic aldehydes to α‐hydroxy ketones, also known as the benzoin condensation, is one of the oldest reactions in organic chemistry. A key intermediate in this reversible reaction is a nitrile‐stabilized carbanion. In 1973 it was shown that these carbanions add irreversibly to α,β‐unsaturated ketones, esters, and nitriles to give 1,4‐diketones, 4‐ketocarboxylic esters, and 4‐ketocarbonitriles, respectively. The reaction succeeds only in aprotic solvents, preferably dimethylformamide. Benzoins and aldehydes can be used interchangeably as starting materials since they are in rapid equilibrium. Cyanide ion catalysis fails with aliphatic aldehydes because they resinify under the strongly basic conditions. Vitamin B1(thiamine) has long been known to convert aliphatic aldehydes into acyloins in buffered aqueous solution. The catalytic effect of vitamin B1is due to the presence of a thiazolium cation. Thiazolium salts in general as well as other azolium salts also catalyze the formation of acyloins. The optimum conditions for thiazolium salt catalysis have been worked out. It was shown subsequently that thiazolium salts, in combination with bases, also catalyze the addition of aliphatic, aromatic, and heterocyclic aldehydes to α,β‐unsaturated carbonyl compounds. The 1,4‐diketones, 4‐ketocarboxylic esters, and 4‐ketocarbonitriles are usually formed in good to excellent yields. Cyanide ion and thiazolium salt catalysis thus complement each other.This chapter covers the literature of the catalyzed nucleophilic addition of aldehydes to electrophilic double bonds up to 1988. The reaction has been reviewed previously.
Divinylcyclopropane‐CycloheptadieneRearrangement
Authors: Hudlicky Tomáš , Fan Rulin , Reed Josephine W. , Gadamasetti Kumar G. 
Published: November 2004

AbstractThe first documented report of a possible Cope rearrangement was probably that of Baeyer, who prepared eucarvone by hydrobromination of carvone in 1894. Although the transformation was briefly studied at that time, it was not until the 1950s that this and other Cope‐type rearrangements received detailed attention. The thermal isomerization ofcis‐divinylcyclopropane to cycloheptan‐1,4‐diene was reported by Vogel in 1960 during his studies of the Cope rearrangement of 1,5‐hexadienes annulated by a homologous series of carbocyclic rings. Scores of mechanistic studies followed this discovery upon the realization that the rearrangement could be related to the conceptually similar vinylcyclopropane–cyclopentene isomerization discovered a year earlier. It was also recognized that this rearrangement might be operating in the formation of cycloheptatriene from norcaradiene during photolysis of diazomethane in benzene. The topic received considerable attention in the 1960s, an era of mechanistic investigations of various concerted transformations. During the 1970s it enjoyed exploitation in many synthetic strategies, and the following decade the elements of this rearrangement were incorporated into tandem or multistep procedures in a preconceived manner. Many aspects of the various permutations of the Cope rearrangement have been previously reviewed.The purpose of this review is to summarize the mechanistic, stereochemical, and practical results in this area in the context of the evolution of synthetic achievements during the last 40 years. Also described in this chapter are the transformations of several of the simple heteroatom permutations of this rearrangement in order to render appropriate comparisons of various systems. A discussion addresses those rearrangements of cyclopropanes, oxiranes, thiiranes, and aziridine rings substituted with vicinal vinyl groups. Excluded from this review are rearrangements of those divinylsubstituted three‐membered rings that contain more than a single heteroatom within the reacting manifold. Brief mention of these systems along with a guide to the literature is found in the last section of this chapter.The literature is covered through December 1990. Many of the principal researchers in this field have been contacted and many unpublished transformations have been included in the tables.
TheBirch Reduction of Aromatic Compounds
Authors: Rabideau Peter W. , Marcinow Zbigniew 
Published: November 2004

AbstractThe reduction of aromatic compounds by alkali metals in liquid ammonia represents an important method for the preparation of partially unsaturated six‐membered rings. The reaction was discovered by Wooster and Godfrey, but the major development resulted from the efforts of A. J. Birch, and the reaction has since come to bear his name. Although a variety of metals can be used, the most common are sodium and lithium, and, to a lesser extent, potassium. Cosolvents such as ether or tetrahydrofuran (THF) are often used to improve solubility, and weak acids such as alcohols may be employed during the reaction as proton sources. The latter are necessary for the reduction of benzene and its unactivated derivatives. Improvement in experimental procedures by Wilds and Nelson, the application to polynuclear compounds by Hückel and later by Harvey, and the development of methods for the alkylation of the anions generated in this process (i.e., reductive alkylation) have made this reaction an important approach to the synthesis of a wide variety of organic compounds.
TheMitsunobu Reaction
Authors: Hughes David L. 
Published: November 2004

AbstractAlkyl and aryl phosphites and phosphines react with compounds having weak heteroatom–heteroatom bonds, such as SS, OO, etc., and with azo compounds to form reactive phosphonium salts. These phosphonium salts in turn promote “redox” condensation reactions with compounds having active hydrogens. The condensation reaction of alcohols using the redox couple of a triaryl‐ or trialkylphosphine and a dialkyl azodicarboxylate has become known as the Mitsunobu reaction, based on his pioneering work in the late 1960s. The overall reaction is summarized, wherein the alcohol (R1OH) and acidic compound (H–Nu) are condensed to form product (R1–Nu), while triphenylphosphine is oxidized to triphenylphosphine oxide and the azodicarboxylate is reduced to the hydrazine. Although the typical redox combination is diethyl azodicarboxylate (DEAD) and triphenylphosphine, many other combinations have found selected use. The reaction is generally limited to primary and secondary alcohols, although tertiary alcohols react in a few intramolecular and intermolecular reactions. For secondary alcohols the reaction usually proceeds with clean inversion of stereochemistry. The acidic component of the reaction generally has an aqueous pKa < 15, with intramolecular reactions providing the exceptions. Examples of H–Nu include oxygen nucleophiles such as carboxylic acids and phenols; nitrogen nucleophiles such as imides, hydroxamates, and heterocycles; sulfur nucleophiles such as thiols and thioamides; and carbon nucleophiles such as β‐ketoesters.Major reviews of the Mitsunobu reaction were published in 1981 by Mitsunobu and in 1983 by Castro. The former review concentrated on reactions using DEAD/triphenylphosphine, while the latter review focused on reactions in which halogens replaced the hydroxy group using reagents such as triphenylphosphine/carbon tetrachloride, triphenyl phosphite/iodomethane, and triphenylphosphine/N‐halosuccinimide. Reactions involving the DEAD/triphenylphosphine redox system are the principal subject of this chapter, with emphasis on the literature between 1981 and 1988.
Anion‐Assisted Sigmatropic Rearrangements
Authors: Wilson Stephen R. 
Published: November 2004

Abstract

The use of sigmatropic rearrangements for the synthesis of organic compounds has become one of the important synthetic tools available to the organic chemist, especially since the development of the detailed stereochemical understanding of these processes in terms of orbital symmetry. The flexibility and predictability of the Cope rearrangement make this type of process widely applicable. The interest and synthetic activity related to the Cope rearrangement can be seen in a previous review of the Claisen and Cope rearrangements. In that review, several variations of the rearrangement were discussed, including examples of the “oxy‐Cope” rearrangement. In 1975 examples of an oxy‐Cope rearrangement were reported wherein an enormous rate acceleration (10
15
) was observed on formation of the potassium salt of the oxy‐Cope substrate.

This chapter surveys extensions of this type of anionic substituent effect to other [3,3]‐, [5,5]‐, [1,3]‐, and [1,5]‐sigmatropic rearrangements as well as retro‐[2 + 2] and reverse Diels–Alder reactions. Specifically excluded are the ester enolate Claisen rearrangement which is mechanistically unrelated, the Wittig rearrangement, and the Haller–Bauer reaction. The chemical literature has been searched to the end of 1989. Emphasis is placed on reactions of synthetic utility, novelty, and generality.
The
N
azarov Cyclization
Authors: Habermas Karl L. , Denmark Scott E. , Jones Todd K. 
Published: November 2004

Abstract
The Nazarov cyclization is named after the eminent Russian chemist I. N. Nazarov (1900–1957). In the course of an extensive study on the formation of allyl vinyl ketones by the mercuric ion and acid‐catalyzed hydration of dienynes, Nazarov and his co‐workers discovered a secondary reaction to form 2‐cyclopentenones. Nazarov initially formulated a direct acid‐catalyzed closure of the allyl vinyl ketones and demonstrated the preparation of 2‐cyclopentenones from these precursors in dozens of cases. However in 1952, Braude and Coles suggested the intermediacy of carbocations and demonstrated that the formation of 2‐cyclopentenones actually proceeds via the α,α′‐divinyl ketones. This fact, together with further mechanistic clarification, has led to the current formulation of the Nazarov cyclization as the acid‐catalyzed closure of divinyl ketones to 2‐cyclopentenones.
This process was already documented in 1903. Treatment of dibenzylideneacetone with concentrated sulfuric acid and acetic anhydride followed by mild alkaline hydrolysis afforded a ketol, the correct structure of which was finally proposed in 1955. Other examples of acid‐catalyzed cyclizations of divinyl ketones exist in the early literature, as do reactions which must have proceeded via divinyl ketones.
A broader definition of the Nazarov cyclization includes a wide variety of precursors that under specific reaction conditions also produce 2‐cyclopentenones via divinyl ketones or their functional equivalents. A case in point is the formation of a cyclopentenone by treatment of either divinyl ketone or tetrahydropyrone with ethanolic hydrochloric acid. It is the structural variety of precursors that lends versatility to the Nazarov cyclization and which also serves as the organizational framework for this chapter.
To facilitate presentation, the reaction is divided into six categories defined by the structure of the precursor: (1) cyclization of divinyl and allyl vinyl ketones, (2) cyclization of silylated (stannylated) divinyl ketones, (3) in situ generation/cyclization of divinyl ketones or equivalents, (4) generation/cyclization of divinyl ketone equivalents by solvolysis, (5) alkyne‐based precursors of divinyl ketones, and (6) coupling reactions to form and cyclize divinyl ketones. The logic of this sequence follows from the order of decreasing structural similarity of the precursors to divinyl ketones. This is intended to be comprehensive in the coverage of cyclizations which produce 2‐cyclopentenones. The related electrocyclic closure of less oxidized pentadienylic cations is not covered. The reaction was most recently reviewed in 1991. Prior to that, the Nazarov cyclization had been reviewed in 1983 and also in the context of pentannulation.
Ketene Cycloadditions
Authors: Hyatt John A. , Raynolds Peter W. 
Published: November 2004

AbstractThe reaction of ketene with itself was described almost simultaneously in 1908 by Chick and Wilsmore in England, and by Staudinger and Klever in Germany; priority for the discovery was attributed to Wilsmore by the German group.Ketene cycloaddition was an early example of a peculiar process, one that formed carbon–carbon bonds with ease, often without the need for solvent, catalyst, or high heat. Subsequent work by others was done in the shadow of Staudinger's exhaustive and rigorous study of all phases of ketene reactivity. Three factors led to a resurgence of interest in this reaction beginning in the 1960s. Haloketenes, which had previously eluded study, were found to have high reactivity, and the halogens could easily be removed after the reaction. The increasing sophistication of powerful analytical methods, particularly nuclear magnetic resonance spectroscopy, led to discovery of the interesting stereochemical aspects of this reaction. Finally, the new theory of orbital symmetry conservation provided a conceptual framework to rationalize these puzzling “no mechanism” reactions.This chapter is a review of cycloaddition reactions of ketenes. Here, a cycloaddition is defined as a reaction of a ketene with an unsaturated organic compound to give a cyclic product by a mechanism that, in principle, involves the almost simultaneous formation of two bonds between two reactants. While there is no concern here as to whether bond formation is concerted or stepwise, no other chemical process can take place between the formation of the first and second bond. Definition here involves both structural and mechanistic factors, and it is difficult to avoid a certain amount of arbitrariness. Products, such as dehydroacetic acid, which seem to us to arise by concatenation of ketene molecules followed by cyclization are excluded. These reactions, are more properly considered to arise from a series of ionic reactions, and the prediction of the eventual product does not take advantage of the special mechanistic features commonly associated with true cycloadditions. Additions to imines to give β‐lactams are numerous and will be covered in a separate review. The literature has been searched to the end of 1988.Many reviews devoted partially or exclusively to ketene cycloadditions have been published. Specific topics that have been reviewed include haloketenes, fluoroketenes, cyanoketenes, intramolecular cycloadditions, conjugated ketenes, and β‐lactam antibiotics. Ancillary topics pertinent to ketene cycloadditions that have been reviewed include cycloreversion reactions, ketene equivalents, which provide ketene functionality with olefin‐like reactivity especially in [4 + 2] reactions, application of frontier molecular orbital theory to cycloadditions, and a critical discussion of cycloadditions with polar intermediates. Applications of cyclobutanones in synthesis have also been reviewed.
Additions of Allyl, Allenyl, and Propargylstannanes to Aldehydes and Imines
Authors: Gung Benjamin W. 
Published: November 2004

Abstract
Natural products that contain stereocenters such as those having polyacetate and polypropionate structures are of considerable interest. Current technology for constructing these chiral molecules consists of strategies broadly defined as “acyclic stereocontrol.” The most efficient tools for this strategy include modern aldol reactions and the reaction of carbonyl compounds with allylmetal reagents. In order to achieve highly efficient syntheses of natural products rich with stereochemistry, highly stereoselective transformations are required. One solution is the use of allylstannane reagents. Their advantages include ease of handling, relative stability, and selective reactivity. The addition of allystannanes to aldehydes combines the process of CC bond formation with the stereoselective production of one or two new stereocenters. The configuration of these centers is predictable based on reaction conditions. Oxygen substitution also contributes to the versatility of these reagents. Recently developed chiral allenystannanes and the use of InCl3 as a transmetallation agent have greatly enhanced the practical utility of these reagents. This chapter is limited mainly to carbonyl and imine addition reactions, most of which create one or two new stereocenters.