Aromatic Substitution Pattern Research Articles

Alkaloids of the Amaryllidaceae. 27. Structures of 9-O-demethylhomolycorine and 5.alpha.-hydroxyhomolycorine. Alkaloids of Crinum defixum, C. scabrum, and C. latifolium. Assignment of aromatic substitution patterns from 1H-coupled carbon-13 spectra

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAlkaloids of the Amaryllidaceae. 27. Structures of 9-O-demethylhomolycorine and 5.alpha.-hydroxyhomolycorine. Alkaloids of Crinum defixum, C. scabrum, and C. latifolium. Assignment of aromatic substitution patterns from 1H-coupled carbon-13 spectraPeter W. Jeffs, Amina Abou-Donia, Dale Campau, and David StaigerCite this: J. Org. Chem. 1985, 50, 10, 1732–1737Publication Date (Print):May 1, 1985Publication History Published online1 May 2002Published inissue 1 May 1985https://doi.org/10.1021/jo00210a031RIGHTS & PERMISSIONSArticle Views287Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (748 KB) Get e-Alerts Get e-Alerts

ChemInform Abstract: CATECHOL O‐METHYLTRANSFERASE. 12. AFFINITY LABELING THE ACTIVE SITE WITH THE OXIDATION PRODUCTS OF 5,6‐DIHYDROXYINDOLE

AbstractDie Acetophenone (I) ergeben über die Carbonsätiren (II) die Alkohole (III), die mit Pyridiniumchlorchromat (PCC) zu den Benzaldehyden (IV) oxidiert werden.

Catechol O-methyltransferase. 12. Affinity labeling the active site with the oxidation products of 5,6-dihydroxyindole.

5,6-Dihydroxyindole (5,6-DHI) and a series of 4- and/or 7-methylated analogues of 5,6-DHI have been synthesized and evaluated for their ability to inactivate purified rat liver catechol O-methyltransferase (COMT). The inactivation of COMT by these agents could be prevented by excluding oxygen from the incubation of mixtures, indicating the necessity for their oxidation to the corresponding aminochromes. Substrate protection studies and kinetic studies suggested that the loss of enzyme activity resulted from the modification of a crucial amino acid residue at the active site of COMT through reaction with the quinoid oxidation products. The COMT inhibitory activity of the 4- and/or 7-methylated analogues of 5,6-DHI argue against a mechanism involving a 1,4 Michael addition reaction at positions 4 or 7 on the aminochrome. Considering the number of potential electrophilic centers on the basic aminochrome structure, the site of the reaction might change depending on the aromatic substitution pattern. The preferred pathway of reaction may be determined in part by the juxtaposition of the protein nucleophile to the possible sites of attack on the electrophilic ligand but also in part on the reactivity of the electrophilic site which might change with substitution on the aromatic ring.

A35512, a complex of new antibacterial antibiotics produced by Streptomyces candidus. II. Chemical studies on A35512B.

The glycopeptide antibiotic A35512B was isolated from Streptomyces candidus NRRL 8156 as the major active factor. Chemical degradation studies showed that mild hydrolysis resulted in the release, one molecule each, of four neutral sugars: rhamnose, fucose, glucose and mannose, as well as the liberation of a complex peptide core which retained all the amino acids and from which 3-amino-2,3,6-trideoxy-3-C-methyl-L-xylo-hexopyranose, a new amino sugar, was isolated (2). Oxidative degradation of A35512B resulted in the isolation of a chlorodiphenylether (5), dimethyl 4-methoxyisophthalate (7) and methyl 3,5-bis-(4-methoxycarbonylphenoxy(-4-methoxybenzoate (6). The structure of 5 could not be conclusively elucidated but was shown to be either 5-chloro-2',3-dimethoxy-2,5'-dicarbomethoxy diphenylether (5a) or 2-chloro-2',3-dimethoxy-5,5'-dicarbomethoxy diphenylether (5b) by physical methods. This halogenated fragment was shown to arise from oxidation of constituent amino acid (10) which has the aromatic substitution pattern of fragment (5a or 5b). Base hydrolysis resulted in the isolation of a phenanthridine (9) which arose from 2',4,6-trihydroxybiphenyl-2,5'-diyldiglycine. These chemical degradation studies on A35512B showed that this antibiotic is closely related to the ristocetin class of antibiotics.

Chemistry of crown ethers: the mass spectra of macrocyclic polyethers

A detailed evaluation of the mass spectral fragmentation patterns of several series of crown ethers has been made. Included are compounds containing one or two aromatic or heteroaromatic rings linked through carbon atoms to polyether chains of various lengths. Although such molecules are highly functionalized and have high molecular weights, molecular ion peaks were always observed, and a large percentage of the total ion current was carried by a small number of fragment ions. Only small differences were observed in the mass spectra of compounds having different aromatic ring substitution patterns. The fragmentation patterns for each set of compounds pointed to the formation of fragment ions in which the positive charge was localized on: (i) ions containing only polyether ring carbon and oxygen atoms; in the majority of cases such an ion (protonated ethylene oxide at m/e 45) provided the base peak: (ii) ions containing the aromatic (heteroaromatic) nucleus and no polyether ring carbon atoms; (iii) ions containing the aromatic (heteroaromatic) nucleus together with part of the polyether chain. High resolution measurements and metastable analysis provided confirmation for the postulated fragmentation mechanisms and product ion structures. Hydrogen and carbon rearrangements are involved in some cases. Components of higher molecular weight crown ether mixtures have been identified by mass spectrometry on the basis of their molecular ion peaks.

Part II ‐ Synthesis, Purification and Characterization of the Pyrazolone Colorants

Thirty‐three substituted pyrazolone colorants have been synthesized, purified and characterized by infrared spectroscopy. These colorants have been shown to be hydrazones rather than azo compounds and, as a result, some infrared assignments made previously in the literature are in error. Definite assignments have been made for five bands characteristic of this system and three additional unassigned bands are indicated. Absorption in 5.98 to 6.08 micrometer range was found to be characteristic of the pyrazolone carbonyl group, while the exocyclic hydrazone double bond appeared at 6.32 to 6.52 μm.* An additional band attributed to the N–H bond in the hydrazone linkage was observed at 7.90 to 8.17 μm.* Absorption associated with endocyclic C=N was assigned in the 6.22–6.35 μm range,† with an additional band at 7.47 to 7.61 μm attributed to ring C–N vibrations.An observed band at 8.58 to 8.81 μm has been assigned to C–N vibration, but its origin is not clear. Although bands at 9.51 to 9.64 μm and 9.87 to 10.06 μm have been assigned to CH3 rock by others, this assignment is considered speculative and these bands are left unassigned. Aromatic substitution patterns in the C–H out‐of‐plane stretching region are also indicated.

The determination of aromatic substitution patterns by nuclear magnetic resonance

AbstractA method is described which permits the analysis of many substituted benzene compounds. The method is useful for mono‐through tetra‐ substituted aromatics. In ideal cases, the number and disposition of the substituents and the chemical shifts of the residual protons can be accurately determined. The method assumes approximate first order couplings and is useful for roughly 50% of all aromatics. Frequently observed anomalous spectra are also discussed.

The mass spectra of dimethoxyamphetam1ne Hydrochlorides

The six dimethoxyamphetamine hydrochlorides give weak but distinguishable mass spectra useful for analytical purposes. The principal fragmentation pathways are discussed in terms of the changing aromatic substitution pattern.