Biosynthesis of aminocyclitol-aminoglycoside antibiotics and related compounds

This review covers the biosynthesis of aminocyclitol-aminoglycoside antibiotics and related compounds, particularly from the molecular genetic perspectives. 195 references are cited.     

Tritium-labeled abscisic acid

A simple method for the preparation of biologically active abscisic acid (growth inhibiting plant hormone) labeled with tritium is described. The product obtained has a specific radioactivity of 1.12 GBq mmol^–1: the yield is about 60% as compared to the initial amount of the substance used.     

The formation and structure of phenylcamphoric acid and related compounds

The complete structure and stereochemistry of (+)-phenylcamphoric acid has been determined. The acid obtained from the Friedel-Crafts reaction of benzene with isolauronolic acid is identified as (±)-phenylcamphoric acid, α-Campholytic acid is shown to be a likely precursor of phenylcamphoric acid in these reactions. The Friedel-Crafts reaction of 3-cyano-1,2,2-trimethylcyclopentanecarbonyl chloride or 3-cyano-2,2-dimethyl-1-methylenecyclopentane with benzene provides a mixture of phenylcamphornitrile and an isomer. Isofenchocamphoric anhydride similarly provides a mixture of the epimeric 4-phenyl-2,2,4-trimethylcyclopentanecarboxylic acids.     

On the relative stereochemistry of atomaric acid and related compounds

The stereochemistry at C-3 of the known compounds atomaric acid 2a, 5′a-desmethyl-5′-acetylatomaric acid 4a, and stypoquinonic acid 5a is revised to 2, 4, and 5 on the basis of a careful study of 2D NOESY experiments and also from comparison of their ¹H and ¹³C chemical shifts with those of the related metabolites 6 and 7 isolated from Stypopodium zonale. Compound 7 is a novel unusually functionalized 1-keto-5′a-desmethyl atomaric acid derivative whose structure and stereochemistry were determined by spectroscopic means.     

Mass spectral fragmentation studies in usnic acid and related compounds

A study of the fragmentation patterns of the naturally occurring lichen substance, usnic acid (I) and various other chemically and biochemically derived compounds is reported and discussed. From these results it is demonstrated that the characteristic fragmentation patterns observed are of considerable utility in determining not only the substitution patterns on these highly oxygenated molecules, but also the structural elucidation of new compounds within the series.     

Ionization potentials and donor properties of nucleic acid bases and related compounds

The first vertical ionization potentials of guanine, adenine, hypoxanthine, xanthine, cytosine, thymine, uracil and purine have been determined by HeI photoelectron spectroscopy. The potentials increase in the above order and are assigned to ionization from the highest π level. The experimental results are compared with valence shell SCF calculations, and the correlation between the association constants of these molecules with riboflavin and their donor properties is discussed. Detailed spectra will be presented and discussed in a forthcoming paper.     

Molecular orbital studies on nicotinic acid,nicotinamide and related compounds

Electronic structures of nicotinic, isonicotinic and 2-picolinic acids and their amides have been investigated, using the variable-α Pariser-Parr-Pople (PPP), iterative extended Hückel and MINDO/2 methods. In addition, PPP and MINDO/2 treatments have also been applied to 3-acetylpyridine and protonated nicotinamide. Based on these calculations, dipole moments, electronic transitions, chemical and biological activity are discussed. Comparison is made with experimental results where available.     

Inclusion complexes of fusidic acid and three structurally related compounds with cyclodextrins

The inclusion complexes between fusidate, 3-keto fusidate, 11-keto fusidate and 11-deoxy fusidate and α-, β-, and γ-cyclodextrin (CD) were studied using capillary electrophoresis. By monitoring the changes in mobility of the negatively charged compounds in the presence of varying amount of CD the stability constants of the complexes formed could be obtained. In the case of α- and β-CD the obtained results could be modelled to a simple model assuming 1:1 stoichiometry, revealing, not surprisingly, that β-CD formed a stronger complex compared to α-CD. A model assuming 1:2 (fusidate:CD) stoichiometry could be fitted to the data obtained with γ-CD. The results showed that the different fusidanes formed very strong 1:1 complexes with γ-CD as well as a quite weak 1:2 complex. 3-keto-, 11-keto- and 11-deoxy-fusidate formed stronger complexes compared to fusidate, probably due to an decrease in hydrophilicity caused by the reduced number of hydroxyl groups. The complex between γ-CD and fusidate was studied by use of 2D-NMR spectroscopy. The results showed that most of the hydrogen atoms of fusidate show interactions with the hydrogen atoms in the cavity of γ-CD. The interaction pattern suggests that fusidate may be fully embedded in the cavity of γ-CD. No interactions between fusidate and the hydrogen atoms situated at the outside of the CD were found.     

Meldrum's acid and related compounds in the synthesis of natural products and analogs

This critical review focuses on applications of Meldrum's acid and its derivatives to the synthesis of natural products and analogs. It covers all relevant literature from 1991 to August 2007 (181 references).     

Benzoxazines and related compounds

The action of a nitrating mixture on 2-substituted 4,4-diethyl-4H-1,3-benzoxazines gives the corresponding 6-nitro derivatives, which can be isolated as such or as the hydrolysis products –N-acyl-,-diethyl-2-hydroxy-5-nitrobenzylamines. The latter cyclize to the corresponding 4H-1,3-benzoxazines under the influence of perchloric acid.See [1] for communication III.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 303–305, March, 1972.