Showing papers on "Diazomethane published in 1987"
TL;DR: N-Acetylneuraminic acid and [6-2H]-Neu5Ac were prepared from 2-acetamido-2-deoxy-D-glucose and the known methyl N-acetyl-4,7,8,9-tetra-O-acetel-2,3-dehydroneuraminate (15), which was identical with a sample prepared from Neu5 Ac.
40 citations
TL;DR: In this paper, a convenient reagent for the preparation of β-lactams from acetic acids and imines is described, and a new route to α-keto-β-Lactams is also reported.
29 citations
TL;DR: In this article, the program PERVAL, based on an all-valence electron perturbation treatment, is applied to the evaluation of cycloadditions of diazomethane.
Abstract: The program PERVAL, based on an all-valence electron perturbation treatment, is applied to the evaluation of cycloadditions of diazomethane. The reactive complexes are modeled after the ab-initio calculated transition state for the reaction of ethylene with diazomethane. The results show the type-I behavior of diazomethane. The reactivity of dipolarophiles in these cycloadditions is determined by CT interactions, the regioselectivity, including the electron-rich methyl vinyl ether, is explained by non-covalent interactions.
Eine PMO-Analyse von Cycloadditionen, IV. –Regioselektivitat und Reaktivitat bei Cycloadditionen des Diazomethans
Das Programm PERVAL, das auf einer alle Valenzelektronen berucksichtigenden Storungstheorie basiert, wird auf Cycloadditionen des Diazomethans angewendet, wobei die reaktiven Komplexe dem ab-initio berechneten Ubergangszustand der Umsetzung von Diazomethan mit Ethylen angepast werden. Die Ergebnisse zeigen, das sich Diazomethan dem Typ I der Klassifikation von Cycloadditionen entsprechend verhalt. Wahrend die Reaktivitat der Dipolarophile gegenuber Diazomethan befriedigend mit CT-Wechselwirkungen erklart werden kann, last sich die Regioselektivitat, einschlieslich der bei der Cycloaddition des elektronenreichen Enolethers beobachteten, am besten mit nichtkovalenten Wechselwirkungen deuten.
24 citations
24 citations
TL;DR: In this paper, 13C NMR spectroscopy is used to examine the hydroxyl group functionality of a series of humic and fulvic acids from different aquatic environments.
24 citations
21 citations
19 citations
TL;DR: In this paper, two synthesises of orellanine, [2,2′-bipyridine]-3,3′, 4,4,4′-tetrol 1,1′-dioxide (5b), are developed which comprise 10 or 11 steps.
16 citations
Journal Article•
16 citations
01 Jan 1987-International Journal of Radiation Applications and Instrumentation. Part A. Applied Radiation and Isotopes
TL;DR: In this paper, a method of synthesis of [11 C]diazomethane from [ 11 C]methane was described, and the specific radioactivity was 92-130 GBq/μmol (2.5-3.5 Ci/μm).
15 citations
TL;DR: It is concluded that the pooled plasma contained only the 17-GAME conjugate, and the natural compound in circulation is 5 alpha-androstane-3 alpha, 17 beta-diol 17-glucuronide.
TL;DR: In this article, an efficient method of protecting the 10,11-double bond in dienone and epoxy enone 16-membered macrolides has been developed, which involves the addition of thioacetic S-acid to the 10-11-ene to give exclusively the 11 -acetylthio derivatives, which can be smoothly deprotected by treatment with fluoride ion.
Abstract: An efficient method of protecting the 10,11-double bond in dienone and epoxy enone 16-membered macrolides has been developed. This involves Michael addition of thioacetic S-acid to the 10,11-ene to give exclusively the 11 -acetylthio derivatives, which can be smoothly deprotected by treatment with fluoride ion. The protected intermediates have been used to prepare a novel class of macrolide antibacterials in which the aldehyde group has been converted into an alkyl ketone by reaction with the appropriate diazoalkane. Thus 20-oxo analogues of rosaramicin, 12,13-de-epoxy-12,13-dehydrorosaramicin, tylosin, and desmycosin have been prepared. The reaction of diazomethane with unprotected macrolides has also been studied including the synthesis of 18-C-methyl-3″-O-propionyll-eucomycin A5. Derivatives in which the 20-formyl group has been replaced by methyl and by halogeno groups, as well as derivatives having a 2,3-ene are described. A number of base-catalyzed rearrangement products including desmycosin 8β,20α-aldol and desmycoin 8α,20β-aldol are also described.
TL;DR: In this article, cyclic meso-dicarboxylic anhydrides are esterified by diphenylboric ester of (R)-2-methoxy-1-phenylethanol in a highly stereoselective manner.
Abstract: In the presence of a catalytic amount of diphenylboryl triflate, cyclic meso-dicarboxylic anhydrides are esterified by diphenylboric ester of (R)-2-methoxy-1-phenylethanol in a highly stereoselective manner, and, after the treatment with diazomethane, the chiral diesters are obtained with high diastereomeric excess.
TL;DR: In this article, Δ4-1,2,4-oxadiazolin-3-carboxylic acids, 3a_3i, were obtained by 1,3-d i polar cycloaddition between Δ2-oxazolin-5-ones, 1, and nitrosobenzene, 2.
TL;DR: Alcohols and phenols adsorbed on silica gel react with diazomethane and quantitatively afford the corresponding methyl ethers as discussed by the authors, and are also effective adsorbents for the reaction.
Abstract: Alcohols and phenols adsorbed on silica gel react with diazomethane and quantitatively afford the corresponding methyl ethers. Alumina and titanium dioxide are also effective adsorbents for the reaction.
TL;DR: In this article, photolysis of diazomethane in acetone yields a carbonyl ylide as an intermediate, which is then used to obtain an intermediate.
TL;DR: In this paper, the chromophoric A-B terminus of orthosomycins was synthesized by esterification of methyl 3-O-benzyl-2,6-didcoxy-α-D-arabino-hexopyranoside with 4-bensyloxy-3,5-dichloro-2-methoxy-6-methylbenzoyl chloride, followed by hydrogenolytic debenzylation.
TL;DR: In this paper, the Wittig condensation was used to synthesize t-butyl 2-ethoxycarbonyl-1-methylcarbapen-1,em-3-exo-carboxylate.
Abstract: t-Butyl 2-ethoxycarbonylcarbapen-1-em-3-exo-carboxylate (7a) has been synthesised by a strategy involving final closure of the 1,2-bond using an intramolecular Wittig condensation. Hydroxyalkylation of the azetidinone nitrogen of 4-vinylazetidin-2-one with t-butyl α,α-dihydroxyacetate followed by treatment of the product (12a) with thionyl chloride–2,6-dimethylpyridine gave t-butyl α-chloro-α(2-oxo-4-vinylazetidin-1-yl)acetate (12b) which underwent chlorine displacement with ethyl (triphenylphosphoranylidene)acetate (10b). The resultant phosphorane (9a) was converted into the carbapen-1-em (7a) by sequential treatment with trifluoroacetic acid, ozone, dimethyl sulphide, and potassium hydrogen carbonate. A similar reaction sequence was used to prepare p-nitrobenzyl 2-ethoxycarbonylcarbapen-1-em-3-exo-carboxylate (7b).An attempt to deprotect the t-butyl ester moiety of compound (7a) with trifluoroacetic acid resulted in β-lactam cleavage to give α-[(2SR,5RS)-4-ethoxycarbonyl-5-t-butoxycarbonyl-1-trifluoroacetyl-2,5-dihydropyrrol-2-yl]acetic acid (21a). Hydrogenolysis of the carbapen-1-em (7b) in the presence of sodium hydrogen carbonate gave initially the sodium salt (7c) and then sodium 2-ethoxycarbonylcarbapenam-3-exo-carboxylate as a 1 : 2 mixture of 2-endo-(24a) and 2-exo-isomers (25a).Whereas hydrogen added predominantly to the endo-face of the alkene moiety of the carbapen-1-em (7a) to give mainly compound (25c), diazomethane attacked largely from the exo-face to give mainly the cycloadduct (32). Under thermal conditions, the last-cited compound was transformed into t-butyl 2-ethoxycarbonyl-1-methylcarbapen-1-em-3-exo-carboxylate (33).Under conditions in which the carbapen-1-em (7a) underwent complete deuterium exchange at position 3, the relative (33) underwent ca. 25% deuterium exchange at position 3.
TL;DR: In this article, a reagent for the stereochemical analysis of chiral inorganic [ 16 O, 17 O, 18 O]thiophosphate was synthesized and treated with the iodo compound.
TL;DR: Deuterium is monitored and quantitated in the presence of hydrogen in organic molecules with the helium microwave emission detector (MED) Various functional groups are tagged utilizing deuterated reagents which also serve to modify the components' Chromatographic characteristics Lithium aluminum deuteride (LAD) will reduce aldehydes, carboxylic acids, esters, amides and acid halides to non-exchangeable CD 2 -tagged alcohols which can be further derivatized with multi-element reagents such as chlorodifluoroacetic anhyd
TL;DR: This chapter describes a method for the separation of molecular species of plant glycolipids and phospholipids by high-performance liquid chromatography without derivatization, whereas lipids having negatively charged residues had to be reacted with diazomethane for satisfactory resolution.
Abstract: Publisher Summary This chapter describes a method for the separation of molecular species of plant glycolipids and phospholipids by high-performance liquid chromatography. The molecular species is separated by several lipids by HPLC without derivatization, whereas lipids having negatively charged residues had to be reacted with diazomethane for satisfactory resolution. The concomitant quantitation at 200 nm depends on the presence of double bonds in the different molecular species. Therefore, completely saturated species can be detected only after conversion of phospho- and glycolipids to the corresponding sn -l,2-diacylglycerols containing a chromophoric acyl substituent at the sn -3 position. Isolated single species may be subjected to HPLC analysis after appropriate quantitative calibration by colorimetry or GLC of fatty acid methyl esters. For this purpose, each species is required in pure form and sufficient quantity, and both absolute and relative response factors are obtained.
TL;DR: X-ray photoelectron spectroscopic evidence was reported for C-C bond formation during the interaction of chemisorbed carbon monoxide with diazomethane on a polycrystalline iron surface as mentioned in this paper.
Abstract: X-Ray photoelectron spectroscopic evidence is reported for C–C bond formation during the interaction of chemisorbed carbon monoxide with diazomethane on a polycrystalline iron surface.
TL;DR: In this article, 3(5)-Carbomethoxy-4-arylpyrazoles can be easily obtained by aromatization with boron trifluoride etherate of 4-aryl-3-acetamido(or benzamido)-3-carbo-methoxy-Δ-pyrazolines synthesized by 1,3-dipolar cyclo addition of diazomethane with 3-aryl 2,3dehydroamino acid derivatives.
TL;DR: In this article, the regio-and stereochemistry of the two possible regioisomers of diazomethane-pyrrolinones is demonstrated by the 1H-nmr data, and the primary adducts originated from the halopyrronones suffer dehydrohalogenation to give aromatized products.
TL;DR: A new optically active phenolic alkaloid with the composition C10H11NO2S, mp 85-88°C, [α]D +28° (c 10; chloroform) (I) has been isolated from the microorganism Pseudomonas aeruginosa (strain 590) and has been called aerugine as discussed by the authors.
Abstract: A new optically active phenolic alkaloid with the composition C10H11NO2S, mp 85–88°C, [α]D +28° (c 10; chloroform) (I) has been isolated from the microorganismPseudomonas aeruginosa (strain 590) and has been called aerugine The action of diazomethane gave an O-methyl derivative (II) On the basis of the formation of ortho-cresol by the hydrogenolytic desulfuration reaction, a study of the IR, mass, and PMR spectra and (I) and its acetyl derivative (III), and also the13C NMR spectrum of (I), the structure of 4-hydroxymethyl-2-(o-hydroxyphenyl)-2-thiazoline has been established for aerugine The spectral characteristics of the compounds mentioned are given
TL;DR: Piperidine-pyrrolidine ring contraction of 1-piperideinium bromide (1) was observed by reaction with aqueous bases, sodium methoxide, phenylhydrazine, (S)-1-phenylethylamine and sodium borohydride, whereas diazomethane addition mainly gave pyrrolo[3,4-b]pyridine derivative 8.
TL;DR: Diazomethane in ethyl ether was added to the carbonyl group of the phenyl trifluoroacetate to yield 2-phenoxy-2-trifluoromethyloxirane as mentioned in this paper.
TL;DR: 3-Methyl(or phenyl)-4-arylhydrazonoisoxazoxazol-5-ones on methylation with diazomethane afford 3-methyl(or pylmethyl)-4-(N-methyl-hydrazono)isoxazone-5.1,2,3-triazoles.