摘要:

AbstractThe majority of folates existing in nature are of the pteroylpolyglutamyl form and are unable to supportLactobacillus caseigrowth until the δ‐linked glutamyls are digested by conjugase enzymes. Most studies involving folate absorption have utilized monoglutamyl forms of folate, primarily folic acid. Synthetic pteroylpolyglutamates prepared by solid phase or conventional synthesis provided conjugated materials with which to study the absorption and metabolism of natural derivatives; however, the synthetic hepataglutamates support microbiological growth prior to enzymatic hydrolysis where as the natural conjugates do not. Incomplete purification of intermediate peptides during the synthesis would be the most likely explanation of this growth phenomenon. A modified solution synthesis has been developed which improves upon intermediate peptide condensations, increases product yields, and provides a heptapeptide which does not support microbiological growth until after enzymatic hydrolys

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270702

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractStable isotope‐labelled tetra‐n‐butyl (124) tin was synthesized by the reaction of n‐butylmagnesium bromide with124SnCl4. Tri‐n‐butyltin bromide was synthesized by bromine cleavage of the tetraalkyltin. The compound can be used to trace chemical, biological and physical processes in environmental and metabolic studies using gas chromatography and electron impact low resolution mass spectrometry. The simplified spectra of the isotopically enriched compounds leads to a twofold increase in detection sensitivi

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270703

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract4‐Nitro[1‐13C]aniline has been prepared in overall yield of 54%, based on labeled acetone, by modification of a standard procedure

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270704

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractA new and efficient synthesis of high specific activity TCH2I containing one atom of tritium per molecule is reported. The precursors for this reagent, chloromethyl p‐phenylbenzoate or bis‐chloromethyl terephthalate, were prepared by the condensation of the corresponding acid chlorides with paraformaldehyde in the presence of zinc chloride. Tritiodehalogenation of the precursors with tritium gas and Pd‐C (10%) in dimethylformamide afforded the desired tritioesters. Cleavage of the esters by lithium iodide at 180°C (SN2type reaction), or by HI at 140°C gave mono tritium labeled methyl iodide in more than 95% yield. The reaction of the latter with a number of amines yielded tritium labeled N‐methylated products readily as was shown by Radio‐HPLC. The specificity of the labeling in the final products was confirmed by tritium nmr s

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270705

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

Abstract2‐14C‐N‐Nitrosothiazolidine was synthesized with a chemical purity of 99.6%, a radio chemical purity of 99.4%, and an overall yield of 30.7%. Unlabelled N‐nitroso‐thiazolidine, synthesized using the same method, resulted in a purity of 99.85% by capillary GC and 99.7% by HPLC. Analysis of N‐nitrosothiazolidine by GC was found to require a low injection port temperature of 160°C to prevent denitrosation in the injection port. During the nitrosation of thiazolidine, if the pH was reduced below 4 with hydrochloric acid, ring hydrolysis occurred, and chlorinated disulfide comp

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270706

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractThe synthesis of 10,10′,19,19,19,19′,19′,19′‐2H8‐β‐carotene is described. The double condensation (C15+C10+C15=C40) of the Wittig salt of 9,9,9,10‐2H4‐β‐ionylidene ethanol with the symmetrical C10dial 2,7‐dimethyl‐2,4,6‐octatrienedial led directly to2H8‐β‐carotene. The symmetrical labelling pattern of this deuterated β‐carotene will function as a tracer for the study

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270707

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractRhodamine‐123 (Rh123) was iodinated with123I in presence of Iodogen. Yield of the labelled Rh123 varied greatly depending upon various reaction parameters. Optimum reaction conditions with respect to molarity and pH of the buffer, reaction time, amounts of iodogen, carrier iodide and Rh123, were determined through carefully controlled reactions. Radiochemical yields of 50–60% were obtained within less than 2 hrs. using 0.05M NH4H2PO4buffer at pH5, 200 μg iodogen, 250 μg Rh123 and no‐carrier‐added iodide. Separation of the labelled Rh123 in greater than 98% radiochemical purity was achieved by flash chromatography on silica gel. The overall isolated yield of radioiodinated Rh123 ranged from 25–35% with respect to the added radioiodide. TLC and HPLC methods were developed for analysis of the labell

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270708

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractLarge kinetic isotope effects have been observed in D‐[6‐3H]galactose enzymatic oxidation reactions catalyzed by the galactoseoxidase. It is possible to use these effects for considerable increase of the molar activity of D‐galactose labelled with tritium in the posit

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270709

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractRacemic d3‐sulpiride, (R)‐(+)‐d3‐sulpiride and (S)‐(−)‐d3‐sulpiride (with three deuterium atoms in the methoxy function ortho to the benzamide), as well as (R)‐(+)‐sulpiride and (S)(−)‐sulpiride were synthesized. The structures were characterized by melting points, IR,1H‐NMR, GC‐MS and polarimetry. The measu

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270710

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY

摘要:

AbstractAromatic nucleophilic substitution of various trimethylammonium trifluoromethanesulfonates with [18F]fluoride has been evaluated. Fluorinations were studied over a temperature range of 45–165°C, with decay corrected yields ranging from 20–80%. [18F]GBR 13119, 1‐[2‐{(4‐[18F]fluorophenyl)(phenyl)methoxy}ethyl]‐4‐(3‐phenylpropyl)piperazine, a potential radio‐tracer for the dopamine uptake system, has been prepared in no‐carrier‐added form from 4‐N,N,N,‐trimethylaniliniumphenylmethanone trifluoromethanesulfonate. Purification by solid‐phase techniques yielded the product in 20% decay corrected radiochemical yield and>98% radiochemical and

ISSN:0362-4803    

DOI:10.1002/jlcr.2580270711

出版商:John Wiley&Sons, Ltd.    

年代:1989

数据来源: WILEY