TERPENOIDS: II. CEANOTHENIC ACID: A C29 A-NORLUPANE DERIVATIVE

1962 ◽  
Vol 40 (8) ◽  
pp. 1632-1641 ◽  
Author(s):  
P. De Mayo ◽  
A. N. Starratt
Keyword(s):  
Carbon Atom ◽  
Dicarboxylic Acid ◽  
Empirical Formula ◽  
The Other ◽  
Carboxyl Group ◽  
Mild Conditions ◽  
Pentacyclic Triterpenoid ◽  
Ceanothus Americanus

Extraction of Ceanothus americanus (Jersey Tea) has afforded a new pentacyclic triterpenoid of the empirical formula C29H42O4. It is a dicarboxylic acid containing two ethylenic linkages. The environment of one carboxyl group and one ethylenic linkage has been shown by diagnostic transformations characteristic of ring E of the lupeol–betulin series. The other ethylenic linkage has been shown to be present in a contracted ring A from which one carbon atom has been lost. The position of the second carboxyl group has been established by introduction of the 11-oxo-12-ene system, when monodecarboxylation occurred under mild conditions. This and other evidence establishes ceanothenic acid to be A-norlupa-1,22-diene-14,17-dicarboxylic acid.

TERPENOIDS: X. PRE-SENEGENIN, A QUITE NORMAL TRITERPENOID

1965 ◽  
Vol 43 (7) ◽  
pp. 2033-2046 ◽  
Author(s):  
J. J. Dugan ◽  
P. de Mayo
Keyword(s):  
Double Bond ◽  
Carbon Atom ◽  
Hydrochloric Acid ◽  
Oleanolic Acid ◽  
Empirical Formula ◽  
Carboxyl Group ◽  
Hydrolytic Cleavage ◽  
Group A

Pre-senegenin has been obtained by a combination of oxidative and hydrolytic cleavage of the saponin, and has been shown to be a member of the normal and unrearranged oleanolic acid series: 2β,27-dihydroxy-23-carboxyoleanolic acid (XXII). On treatment with ethanolic hydrochloric acid it is converted quantitatively to a mixture of polygalic acid (XXI) and senegenin.Previous work (1) has shown that senegenin is a triterpenoid of empirical formula C30H45O6Cl with a 2β,3β-glycol system and a 4α-carboxyl group. A second carboxyl group is also present. It has now been found to be a member of the β-amyrin-oleanolic acid series in which a carbon atom at C14 has migrated to C12 with concomitant movement of the double bond to the C13—C14 position, and that it has the structure (XX).

scholarly journals Hydrogenation of benzoic acid derivatives over Pt/TiO2 under mild conditions

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Miao Guo ◽  
Xiangtao Kong ◽  
Chunzhi Li ◽  
Qihua Yang
Keyword(s):  
Electron Transfer ◽  
Benzoic Acid ◽  
High Efficiency ◽  
Carboxyl Groups ◽  
Carboxyl Group ◽  
Benzoic Acids ◽  
Catalyst Poisoning ◽  
Benzoic Acid Derivatives ◽  
Mild Conditions ◽  
Transfer Direction

AbstractHydrogenation of benzoic acid (BA) to cyclohexanecarboxylic acid (CCA) has important industrial and academic significance, however, the electron deficient aromatic ring and catalyst poisoning by carboxyl groups make BA hydrogenation a challenging transformation. Herein, we report that Pt/TiO2 is very effective for BA hydrogenation with, to our knowledge, a record TOF of 4490 h−1 at 80 °C and 50 bar H2, one order higher than previously reported results. Pt/TiO2 catalysts with electron-deficient and electron-enriched Pt sites are obtained by modifying the electron transfer direction between Pt and TiO2. Electron-deficient Pt sites interact with BA more strongly than electron-rich Pt sites, helping the dissociated H of the carboxyl group to participate in BA hydrogenation, thus enhancing its activity. The wide substrate scope, including bi- and tri-benzoic acids, further demonstrates the high efficiency of Pt/TiO2 for hydrogenation of BA derivatives.

Dative behavior of N-heterocyclic carbenes (NHCs) with selenium in Se-NHC compounds

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Munazzah Yaqoob ◽  
Mahvish Abbasi ◽  
Hira Anwar ◽  
Javed Iqbal ◽  
Mohammad Asad ◽  
...  
Keyword(s):  
Nitrogen Atom ◽  
Carbon Atom ◽  
Lone Pair ◽  
Heterocyclic Ring ◽  
Heterocyclic Carbenes ◽  
The Other ◽  
Donor Ligands ◽  
Important Research ◽  
Dative Bond ◽  
Back Bonding

Abstract N-heterocyclic carbenes (NHCs) are an eminent class of carbenes having a heterocyclic ring in which a divalent carbon atom is attached directly to a nitrogen atom. In the NHCs, the donation of lone pair is another important research in the dative bonding and not only in NHCs the dative bond plays a functionalized role in the other classes of complex formation like ylidones L → E ← L and carbones L → C ← L. M–NHC bond is L-M sigma-dative bond and NHCs are considered as strong sigma-donor ligands. The clear picture of the M–NHC bond can be better understood by M–NHC pi-interaction. M-L pi interaction is comprised of two steps. One is L → M sigma-donation and M → L π* back bonding. This dative donor nature of NHC and also its behavior in organoselenium is studied through DFT in which it’s optimized structure, bond lengths, molecular vibrations are calculated.

scholarly journals On Governance and the Demographic Transition

2012 ◽  
Vol 4 (6) ◽  
pp. 319-330
Author(s):  
Flaubert Mbiekop
Keyword(s):  
Demographic Transition ◽  
Financial Support ◽  
Overlapping Generations ◽  
The Other ◽  
Overlapping Generations Model ◽  
Child Quality ◽  
Mild Conditions ◽  
Weak Institutions ◽  
The One ◽  
Fertility Choices

It is now conventional wisdom that institutions shape household fertility choices, especially in developing countries. However, deeper insights into the mechanisms at play are still needed. This paper develops a game-theoretical framework with a simple overlapping-generations model to show how a typical household may come to prefer bearing and raising numerous children as a savings scheme for retirement and not rely on conventional outlets for saving when facing weak institutions. On the one hand weak institutions increase the risk that individuals may lose their savings if relying on conventional outlets. On the other hand, childbearing as an investment/savings scheme carries with it the risk that disguised or complete unemployment may prevent grown children from providing the expected old-age financial support. The typical household thus trades off between both types of risks, yet with more control in the latter case, as the likelihood of unemployment can be reduced by carefully selecting a child quality-quantity strategy. Mild conditions are sufficient to show that sound institutions induce less fertility and foster private saving and oldage consumption. A simple voting experiment unveils a tricky socio- economic dynamics whereby wealthier households may have stakes supporting weak institutions.

Dicarboxylic acid esters from the carbonylation of unsaturated esters under mild conditions

2005 ◽  
Vol 8 (10) ◽  
pp. 878-881 ◽  
Author(s):  
Cristina Jiménez-Rodriguez ◽  
Graham R. Eastham ◽  
David J. Cole-Hamilton
Keyword(s):  
Dicarboxylic Acid ◽  
Unsaturated Esters ◽  
Mild Conditions ◽  
Acid Esters

An Empirical Formula to Estimate the Resistance of a Convoy in a Restricted Waterway

1996 ◽  
Vol 40 (02) ◽  
pp. 107-111
Author(s):  
J.L.J. Marchal ◽  
Y.-D. Shen ◽  
D. Kicheva
Keyword(s):  
Cross Section ◽  
Empirical Formula ◽  
The Other ◽  
Total Resistance ◽  
Empirical Methods ◽  
Joint Research ◽  
Ship Hydrodynamics ◽  
Joint Research Project ◽  
Length Width ◽  
The Subject

An examination of the literature produced very few references related to the subject of estimating the resistance of a convoy navigating in a waterway of limited cross section. This paper reports the findings of one such study—a joint research project undertaken by Belgium's University of Liege and the Bulgarian Ship Hydrodynamics Centre. A polynomial is presented here for evaluating the total resistance of a convoy moving in a restricted waterway. The resistance was found to depend on Froude number and on the relative dimensions (length, width and depth) between the convoy and the channel. The results obtained by the suggested polynomial are compared with those obtained by the other three existing empirical methods.

Zur Biosynthese der Benzoesäure in Gaultheria procumbens L. II

1964 ◽  
Vol 19 (9) ◽  
pp. 781-783 ◽  
Author(s):  
Hans Grisebach ◽  
Karl-Otto Vollmer
Keyword(s):  
Salicylic Acid ◽  
Cinnamic Acid ◽  
Protocatechuic Acid ◽  
Total Activity ◽  
Syringic Acid ◽  
The Other ◽  
Carboxyl Group ◽  
Hydroxybenzoic Acid ◽  
Benzoic Acids ◽  
Gaultheria Procumbens

Further investigations on the biosynthesis of benzoic acids in Gaultheria procumbens L. have shown that besides salicylic acid all the other benzoic acids (gentisinic acid, p-hydroxybenzoic acid, protocatechuic acid, o-pyrocatechuic acid(?), syringic acid and vanillinic acid) can be formed from cinnamic acid. In the case of vanillinic acid it was proved that the total activity is located in the carboxyl group when cinnamic acid-[3-14C] is the precursor.Formiat-14C is incorporated into the methylester group of methylsalicylate.

Selenosilane-Promoted Selective Mild Transformation of N-Thiophthalimides into Symmetric Disulfides

Synthesis ◽  
2019 ◽  
Vol 51 (08) ◽  
pp. 1819-1824 ◽  
Author(s):  
Caterina Viglianisi ◽  
Chiara Bonardi ◽  
Elena Ermini ◽  
Antonella Capperucci ◽  
Stefano Menichetti ◽  
...  
Keyword(s):  
The Other ◽  
Chemical Behavior ◽  
Simple Method ◽  
Mild Conditions ◽  
Other Hand ◽  
Dialkyl Disulfides

The reactivity of N-thiophthalimides with silyl chalcogenides is described. Treatment of N-thiophthalimides with bis(trimethylsilyl) sulfide [(Me3Si)2S] leads to the formation of a mixture of the corresponding disulfides and trisulfides. On the other hand, N-thiophthalimides react with bis(trimethylsilyl) selenide [(Me3Si)2Se] under TBAF catalysis to smoothly give variously substituted diaryl, divinyl, and dialkyl disulfides; formation of a selenotrisulfide (dithiaselane, RSSeSR) is rationalized as an intermediate. Exploiting the different chemical behavior of silyl chalcogenides, we have disclosed a novel, selective, and operationally simple method to access disulfides in good yields under mild conditions.

scholarly journals SEROLOGICAL STUDIES ON AZOPROTEINS

1934 ◽  
Vol 59 (6) ◽  
pp. 751-768 ◽  
Author(s):  
E. Landsteiner ◽  
J. van der Scheer
Keyword(s):  
Carbon Atom ◽  
Physicochemical Properties ◽  
Fumaric Acid ◽  
Glutaric Acid ◽  
Carboxyl Group ◽  
Trans Isomers ◽  
Serological Studies ◽  
Serological Specificity ◽  
Influence Of Substituents ◽  
Aliphatic Chains

A study was made of the specificity of artificial compound-antigens containing aliphatic chains. Striking specificity was exhibited in the reactions of compounds with short chains containing a carboxyl group; for instance succinic acid could be differentiated from malonic or glutaric acid which contain one fewer and one more carbon atom respectively. With the substances containing longer chains, reactions were observed which, although specific to a certain extent, appear to depend mainly on the general physicochemical properties of long aliphatic chains. With a limited number of substances the influence of substituents —halogen, OH, NH2—on the serological specificity was investigated. By means of inhibition reactions it was possible to demonstrate the serological specificity of cis-trans isomers such as maleic and fumaric acid.

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