Reaction of peri-Aminonaphthoquinones and Dihydroperimidinones with piperidine

1977 ◽  
Vol 30 (9) ◽  
pp. 2081 ◽  
Author(s):  
DW Cameron ◽  
EL Samuel
Keyword(s):  
Side Chain ◽  
Methyl Group ◽  
System 1

Reaction of methyl-substituted 5-amino-1,4-naphthoquinones with piperidine gave preferentially 3-piperidino derivatives. The corresponding orientation also resulted from amination of the dihydroperimidinone system (1), a slower process. When position 3 of the naphthoquinone was substituted by a methyl group, preferential side-chain amination of that group was observed.

scholarly journals Effect of side-chain length in lignin model compound on MnO2 oxidation: comparison of oxidations between C6-C2- and C6-C1-type compounds

2021 ◽  
Vol 67 (1) ◽  
Author(s):  
Shirong Sun ◽  
Tomoya Yokoyama
Keyword(s):  
Isotope Effects ◽  
Aromatic Nucleus ◽  
Side Chain ◽  
Direct Oxidation ◽  
Initial Oxidation ◽  
Methyl Group ◽  
Lignin Model Compound ◽  
Oxidation Rates ◽  
Kinetic Isotope ◽  
Lignin Model

AbstractMonomeric C6-C2-type lignin model compounds with a p-hydroxyphenyl (H), guaiacyl (G), syringyl (S), or p-ethylphenyl (E) nucleus (1-phenylethanol derivatives) were individually oxidized by MnO2 at a pH of 1.5 and room temperature. The results were compared with those of the corresponding C6-C1-type benzyl alcohol derivatives obtained in our recent report to examine the effect of the presence of the β-methyl group on the oxidation. The presence decelerated the oxidation regardless of the type of aromatic nucleus, although it did not change the order of the oxidation rates: G > S >> H > E. This deceleration results from the steric factor of the β-methyl group in the C6-C2-type compounds. The MnO2 oxidations of the corresponding C6-C2-type compounds deuterated at their α-(benzyl)positions showed that the magnitudes of the kinetic isotope effects are smaller than those observed in the oxidations of the corresponding C6-C1-type compounds, regardless of the type of aromatic nucleus. These smaller magnitudes suggest that the presence of the β-methyl group shifts the initial oxidation mode of MnO2 from direct oxidation of the benzyl position to one-electron oxidation of the aromatic nucleus. Only the S-type compounds afforded products via degradation of the aromatic nuclei.

The Rates and Products of Addition of 4-Chlorobenzenesulfenyl Chloride to a Series of Side Chain Methyl Substituted Styrenes

1974 ◽  
Vol 52 (9) ◽  
pp. 1807-1812 ◽  
Author(s):  
George H. Schmid ◽  
Dennis G. Garratt
Keyword(s):  
Steric Hindrance ◽  
Side Chain ◽  
Methyl Groups ◽  
Methyl Group

The rates of addition and the product compositions have been determined for the addition of 4-chlorobenzenesulfenyl chloride to a series of seven side chain methyl substituted styrenes in 1,1,2,2-tetrachloroethane at 25°. Unlike the addition to the corresponding series of methylated ethylenes, the effect of the methyl groups is not cumulative. The effect of the methyl groups depends upon whether or not the β-methyl group is cis to the phenyl. When it is cis, the rate of addition is decreased compared to styrene and substitution of additional methyl groups has only a small effect on the rate of addition. In compounds lacking a cis-β-methyl group the rate of addition more closely resembles that for addition to the methylated ethylenes. Steric hindrance between the cis-methyl and phenyl groups is believed to be the cause of this difference in behavior between the ethylene and styrene series.

Synthesis of Side-Chain Locked Analogs of 1α,25-Dihydroxyvitamin D3 Bearing a C17 Methyl Group

2018 ◽  
Vol 20 (9) ◽  
pp. 2641-2644 ◽  
Author(s):  
Rita Sigüeiro ◽  
Miguel A. Maestro ◽  
Antonio Mouriño
Keyword(s):  
Side Chain ◽  
Dihydroxyvitamin D3 ◽  
Methyl Group

The Conformation of the Side Chain of 21-Alkylpregnanes

2003 ◽  
Vol 2003 (9) ◽  
pp. 556-558 ◽  
Author(s):  
James R. Hanson ◽  
Peter B. Hitchcock ◽  
Jorge A.R. Salvador
Keyword(s):  
Crystal Structures ◽  
Side Chain ◽  
Methyl Group ◽  
X Ray

The X-ray crystal structures of some 21-alkylpregnanes have been determined and the effects of a 16α,17α-epoxide and 21-methyl group on the conformation of the side chain are discussed.

STUDIES ON THE TISSUE-DISPOSITION AND FATE OF [14C]STREPTOZOTOCIN WITH SPECIAL REFERENCE TO THE PANCREATIC ISLETS

1978 ◽  
Vol 89 (2) ◽  
pp. 339-351 ◽  
Author(s):  
Eva Britt Johansson ◽  
Hans Tjälve
Keyword(s):  
Pancreatic Islets ◽  
High Capacity ◽  
Whole Body ◽  
Side Chain ◽  
High Accumulation ◽  
Methyl Group ◽  
Whole Body Autoradiography ◽  
Selective Labelling ◽  
Chinese Hamsters ◽  
Tissue Disposition

ABSTRACT The tissue-disposition and fate of [14C]streptozotocin, labelled in the methyl-group of the N-nitrosomethylurea side-chain, have been studied in mice. Whole-body autoradiography, quantified by densitometric measurements, showed that the pancreatic islets had a high capacity to accumulate radioactivity after the injection of [14C]streptozotocin. Microautoradiography of the pancreas showed that centrally located cells were labelled while peripherally located cells contained a low labelling, indicating a selective labelling of the β-cells. A high radioactivity was present in the liver and the cortex of the kidney at most survival intervals. About 17 % of the radioactivity was exhaled as 14CO2 during 6 h, which shows that the methyl group of the N-nitrosomethylurea side-chain is split off. Radioactivity was shown to be incorporated in the acid-insoluble precipitate of the pancreatic islets, the liver, the kidney, and the exocrine pancreas. This may, to a varying extent, be due both to alkylating reactions and to incorporation of radioactivity in the macromolecules of the tissues via normal metabolic pathways. About 44 % of the radioactivity was excreted as unchanged [14C]streptozotocin in the urine during 24 h, while about 1 % of the radioactivity was found in the faeces. Whole-body autoradiography of [14C]streptozotocin in two Chinese hamsters and one rat also showed a high accumulation of radioactivity in the pancreatic islets in these species.

scholarly journals Nitration of the tetramethylbenzenes in acetic anhydride. Formation and rearomatization of adducts

1976 ◽  
Vol 54 (11) ◽  
pp. 1795-1806 ◽  
Author(s):  
Alfred Fischer ◽  
David R. A. Leonard
Keyword(s):  
Acetic Anhydride ◽  
Side Chain ◽  
Methyl Group ◽  
Nitro Derivatives

Nitration of the tetramethylbenzenes in acetic anhydride at temperatures below –50 °C gives the l-acetoxy-4-nitro and 5-acetoxy-2-nitro adducts from the 1,2,3,4 isomer, the 5-acetoxy-2-nitro adduct from the 1,2,3,5 isomer, and the l-acetoxy-4-nitro adduct from the 1,2,4,5 isomer as well as the expected nitro derivatives. Corresponding nitritonitro adducts are also formed as well as side-chain (benzylic) derivatives: nitrates and phenylnitromethanes. Rearomatization of the tertiary acetate adducts leads to aryl acetates, benzylic derivatives, or nitroarenes, depending upon the acidity of the solvent. In the benzylic derivatives the methyl group substituted is that ipso to the acetate in the precursor adduct, that para to the most activated ipso position of the arene.

scholarly journals Modifications of the acyl-d-alanyl-d-alanine terminus affecting complex-formation with vancomycin

1971 ◽  
Vol 123 (5) ◽  
pp. 789-803 ◽  
Author(s):  
M. Nieto ◽  
H. R. Perkins
Keyword(s):  
Complex Formation ◽  
Cell Walls ◽  
Solid Phase ◽  
Side Chain ◽  
Stable Complex ◽  
Cross Link ◽  
Methyl Group ◽  
The Third ◽  
Carboxyl Terminal ◽  
Better Than

Vancomycin forms complexes with peptides terminating in d-alanyl-d-alanine that are analogous to the biosynthetic precursors of bacterial mucopeptides. The specificity of complex-formation has been studied by means of many synthetic peptides, prepared by both solid-phase and conventional methods. The following conclusions can be drawn: (a) three amide linkages are required to form a stable complex; (b) the terminal carboxyl group must be free; (c) the carboxyl terminal and subterminal residues must be either glycine or of the d-configuration; (d) the size of the side chain in these residues greatly influences the affinity for vancomycin, a methyl group being the optimum in each case; (e) the nature of the side chain in the third and fourth residues has a smaller effect on complex-formation, but an l-configuration was somewhat better than a d-configuration in the third position. In addition to acyl-d-alanyl-d-alanine, other peptides that occur in bacterial cell walls will combine with vancomycin, although less strongly, e.g. acyl-d-alanyl-d-α-amino acid (where the terminal d-residue may form the cross-link in mucopeptide structure) and acyl-l-alanyl-d-glutamylglycine (a sequence found in the mucopeptide of Micrococcus lysodeikticus and related organisms). These results throw some light on the specificity of the uptake of vancomycin by living bacteria.

Pterins. VIII. The absolute configuration at C 6 of natural 2-Amino-6-[(1'R,2'S)- 1',2'-dihydroxypropyl]-5,6,7,8-tetrahydropteridin-4(3H)-one (L-erythro-5,6,7,8-tetrahydrobiopterin)

1982 ◽  
Vol 35 (4) ◽  
pp. 785 ◽  
Author(s):  
WLF Armarego ◽  
P Waring ◽  
B Paal
Keyword(s):  
Hydrochloric Acid ◽  
Absolute Configuration ◽  
Side Chain ◽  
Methyl Group ◽  
Convenient Synthesis ◽  
The Absolute

The conformation of the side chain of 5,6,7,8-tetrahydrobiopterint (6) in 0.5 M DCl/D2O is predominantly quasi-equatorial (deduced from 3J (13C4a, 1H6) 1.1 HZ), and is the same as that of the methyl group in 2-methyl-1,2,3,4-tetrahydroquinoxaline and in 2-amino-6-methyl-5,6,7,8-tetrahydropteridin-4(3H)-one in the same solvent. Because (-)-(2S)-2-methyl-1,2,3,4-tetrahydroquinoxaline(4) and (-)-(6S)-2-amino-6-methyl-5,6,7,8-tetrahydropteridin-4(3H)-one (5) have the same conformation and negative c.d. spectra (O 248 nm and 263 nm respectively) as does the natural 5,6,7,8, tetrahydrobiopterin (O minimum at 265 nm) in 0.1 M hydrochloric acid, then the absolute conformations of the tetrahydropyrazine rings and the absolute configurations at the chiral centres C2, C6, and C6 of compounds (4), (5) and (6) respectively are the same. Hence the absolute configuration at C6 in natural 5,6,7,8 tetrahydrobiopterin is R.� A convenient synthesis of biopterin on a gram scale is described.

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