scholarly journals A total synthesis of myrrhine, (±)-hippodamine, and (±)-convergine

1976 ◽  
Vol 54 (3) ◽  
pp. 473-481 ◽  
Author(s):  
William A. Ayer ◽  
Robin Dawe ◽  
Reinhold A. Eisner ◽  
Kimiaki Furuichi
Keyword(s):  
Acetic Acid ◽  
Total Synthesis ◽  
Carbonyl Group ◽  
Acid Catalyzed ◽  
Defensive Substance ◽  
Hydrolysis Of ◽  
Alcohol Reduction

A seven-step, stereoselective, total synthesis of the ladybug defensive substance myrrhine (5) from 2,4,6-collidine is presented. Successive alkylation and acylation of 2,4,6-collidine followed by ketalization provides 2-(3-[2-(1,3-dioxolanyl)]propyl)-6-(2-methyl-2-[1,3-dioxolanyl]methyl)-4-methylpyridine (14). Sodium–alcohol reduction gives the corresponding all-cis piperidine 17. Hydrolysis of 17 followed by acid-catalyzed cyclization provides ketone 26. Reduction of the carbonyl group in 26 gives myrrhine (5). Cyclization using pyrrolidine – acetic acid gives a mixture of ketones (26 and 31). Reduction of 31 gives (±)-hippodamine (4). Oxidation of (±)-hippodamine with peracid gives (±)-convergine (3).

Hydration of the carbonyl group — Acetic acid catalysis in the co-operative mechanism

2005 ◽  
Vol 83 (6-7) ◽  
pp. 769-785 ◽  
Author(s):  
Yih-Huang Hsieh ◽  
Noham Weinberg ◽  
Kiyull Yang ◽  
Chan-Kyung Kim ◽  
Zheng Shi ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Carbonyl Group ◽  
Isotope Shift ◽  
Acid Catalysis ◽  
Water Molecules ◽  
Hydration Reaction ◽  
Water Solvent ◽  
General Acid ◽  
O Isotope ◽  
Acid Catalyzed

In a co-operative reaction, solvent molecules, specifically water molecules, participate actively in the mechanism to circumvent the formation of charged intermediates. This paper extends our earlier theoretical treatment of the neutral co-operative hydration of acetone to include general acid catalysis by acetic acid. As before, the predominant neutral channel employs three catalytic water molecules. The principal acetic acid catalyzed channels employ one catalytic water molecule and, in approximately equal proportions, one or both oxygens of the carboxyl group. The theoretical rate constant for general acid catalysis is calculated to be 0.49 M–1 s–1 at 298 K. This compares to an estimated experimental value of 0.30 M–1 s–1 for acetic acid catalyzed hydration of acetone at 298 K in water solvent, determined by using the 18O-isotope shift in the 13C NMR spectrum of 2-13C-labelled acetone as a kinetic probe. It is concluded that the notion of co-operativity can be extended to include general acid catalysis of the hydration of a carbonyl group in water solvent. This creates an obvious problem for the generally accepted view that multistep ionic mechanisms are operative in the low dielectric media that exist at the active sites of hydrolytic enzymes. The relevance of this finding to the mechanisms of action of β-lactam antibiotics has been noted.Key words: hydration, reaction mechanism, co-operativity, general acid catalysis, ab initio, SCRF, 18O-isotope shift.

Total Synthesis of DL-Glucose, 3-O-Methyl-DL-glucose, and 3-Deoxy-DL-ribo-hexopyranose from 1,6:3,4-Dianhydro-β-DL-allo-hexopyranose, a Product Obtained from Acrolein Dimer

1971 ◽  
Vol 49 (20) ◽  
pp. 3342-3347 ◽  
Author(s):  
U. P. Singh ◽  
R. K. Brown
Keyword(s):  
Total Synthesis ◽  
Acid Hydrolysis ◽  
Sodium Methoxide ◽  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Barium Hydroxide ◽  
Lithium Aluminum ◽  
Methyl Glycoside ◽  
Acid Catalyzed ◽  
Hydrolysis Of

The reaction of butyllithium in ether with 1,6:2,3-dianhydro-4-deoxy-β-DL-ribo-hexopyranose (1), a substance obtained in five steps from acrolein dimer, gave 1,6-anhydro-3,4-dideoxy-β-DL-erythro-hex-3-enopyranose (2). The compound 1,6:3,4-dianhydro-β-DL-allo-hexopyranose (3), obtained from 2, was converted by reaction with aqueous barium hydroxide followed by hydrolysis of the product, to DL-glucose 5. Treatment of 3 with sodium methoxide in methanol followed by acid hydrolysis of the 1,6-anhydro intermediate 6, gave 3-O-methyl-DL-glucose (7). The same intermediate, 6, along with the methyl glycoside 8, could be obtained by the acid-catalyzed reaction of 3 with methanol. Lithium aluminum hydride reacted with 3 to form 1,6-anhydro-3-deoxy-β-DL-ribo-hexopyranose (9), which was hydrolyzed readily to 3-deoxy-DL-ribo-hexopyranose (10).Yields were excellent throughout. All products obtained from the oxirane 3 were those resulting only from trans diaxial opening of the oxirane ring.

Simplified Rapid Technic for the Extraction and Determination of Serum Cholesterol without Saponification

1956 ◽  
Vol 2 (5) ◽  
pp. 353-368 ◽  
Author(s):  
Julius J Carr ◽  
I J Drekter
Keyword(s):  
Acetic Acid ◽  
Acetic Anhydride ◽  
Total Cholesterol ◽  
Simple Procedure ◽  
Cholesterol Esters ◽  
Color Development ◽  
Acid Catalyzed ◽  
Hydrolysis Of ◽  
Room Lighting

Abstract An accurate yet simple procedure for the determination of total cholesterol, based upon the application of a Liebermann-Burchard color reaction directly in the solvent employed for extraction of cholesterol from serum, has been described. Extraction of cholesterol and removal of protein are accomplished by means of acetic acid and acetic anhydride. Serum water is removed by the acid-catalyzed hydrolysis of acetic anhydride. The Liebermann-Burchard color is then developed with a stable, modified reagent consisting of equal volumes of H2SO4 and acetic acid. Excellent agreement with the technic of Schoenheimer and Sperry is obtained. Equal intensities of color are produced by equivalent concentrations of free and esterified cholesterol. Preliminary saponification of cholesterol esters is therefore not required. Color development may proceed in ordinary room lighting without loss of accuracy.

Organic material dissolved during oxygen-alkali pulping of hot water extracted birch sawdust

TAPPI Journal ◽  
2015 ◽  
Vol 14 (4) ◽  
pp. 237-244 ◽  
Author(s):  
JONI LEHTO ◽  
RAIMO ALÉN
Keyword(s):  
Acetic Acid ◽  
Betula Pendula ◽  
Cooking Time ◽  
Hot Water ◽  
Partial Hydrolysis ◽  
Chemical Pulping ◽  
Black Liquors ◽  
Aliphatic Carboxylic Acids ◽  
Hydrolysis Of ◽  
Cooking Conditions

Untreated and hot water-treated birch (Betula pendula) sawdust were cooked by the oxygen-alkali method under the same cooking conditions (temperature = 170°C, liquor-to-wood ratio = 5 L/kg, and 19% sodium hydroxide charge on the ovendry sawdust). The pretreatment of feedstock clearly facilitated delignification. After a cooking time of 90 min, the kappa numbers were 47.6 for the untreated birch and 10.3 for the hot water-treated birch. Additionally, the amounts of hydroxy acids in black liquors based on the pretreated sawdust were higher (19.5-22.5g/L) than those in the untreated sawdust black liquors (14.8-15.5 g/L). In contrast, in the former case, the amounts of acetic acid were lower in the pretreated sawdust (13.3-14.8 g/L vs. 16.9-19.1 g/L) because the partial hydrolysis of the acetyl groups in xylan already took place during the hot water extraction of feedstock. The sulfur-free fractions in the pretreatment hydrolysates (mainly carbohydrates and acetic acid) and in black liquors (mainly lignin and aliphatic carboxylic acids) were considered as attractive novel byproducts of chemical pulping.

Arylboronic Acid-Catalyzed C-Allylation of Unprotected Oximes

2019 ◽  
Author(s):  
Juha Siitonen ◽  
Padmanabha V. Kattamuri ◽  
Muhammed Yousufuddin ◽  
Laszlo Kurti
Keyword(s):  
Total Synthesis ◽  
Acid Catalysts ◽  
Mechanistic Studies ◽  
Arylboronic Acid ◽  
Synthetic Utility ◽  
Acid Catalyzed

Unprotected keto- and aldoximes are readily <i>C</i>-allylated with allyl diisopropyl boronate in the presence of arylboronic acid catalysts to yield highly-substituted <i>N</i>-alpha-secondary (2°) and tertiary (3°) hydroxylamines. The method’s synthetic utility is demonstrated with the total synthesis of the trace alkaloid <i>N</i>-methyl-euphococcine. Preliminary experimental and computational mechanistic studies point toward the formation of a boroxine as the active allylating species.<br>

Total Synthesis and Antibacterial Screening of (±)-6,8-Dihydroxy-3- undecyl-3,4-dihydroisochromen-1-one: A Structural Analogue of Metabolites from Ononis natrix

2019 ◽  
Vol 16 (3) ◽  
pp. 245-248
Author(s):  
Hummera Rafique ◽  
Aamer Saeed ◽  
Ehsan Ullah Mughal ◽  
Muhammad Naveed Zafar ◽  
Amara Mumtaz ◽  
...  
Keyword(s):  
Total Synthesis ◽  
Structural Analog ◽  
Diffusion Method ◽  
Bacterial Strains ◽  
Antibacterial Screening ◽  
Maximum Inhibition ◽  
Bacillus Subtilus ◽  
Hydrolysis Of ◽  
Direct Condensation

Background: (±)-6,8-Dihydroxy-3-undecyl-3,4-dihydroisochromen-1-one is one of the structural analog of several substituted undecylisocoumarins isolated from Ononis natrix (Fabaceae), has been successfully synthesized by direct condensation of homopthalic acid (1) with undecanoyl chloride yields isochromen-1-one (2). Methods: Alkaline hydrolysis of (2) gave the corresponding keto-acid (3), which is then reduced to hydroxy acid (4) then its cyclodehydration was carried out with acetic anhydride to afford 3,4- dihydroisochromen-1-one (5). Followed by demethylation step, the synthesis of target 6,8- dihydroxy-7-methyl-3-undecyl-3,4-dihydroisocoumarin (6) was achieved. Results: In vitro antibacterial screening of all the synthesized compounds were carried out against ten bacterial strains by agar well diffusion method. Conclusion: Newly synthesized molecules exhibited moderate antibacterial activity and maximum inhibition was observed against Bacillus subtilus and Salmonella paratyphi.

The effect of polymeric and model imidazolium halides on the rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid

1985 ◽  
Vol 50 (4) ◽  
pp. 845-853 ◽  
Author(s):  
Miloslav Šorm ◽  
Miloslav Procházka ◽  
Jaroslav Kálal
Keyword(s):  
Catalyst Concentration ◽  
Low Molecular Weight ◽  
Imidazolium Chloride ◽  
First Order ◽  
Nitrobenzoic Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Hydrolysis Of ◽  
Ethanol In Water ◽  
Direct Attack

The course of hydrolysis of an ester, 4-acetoxy-3-nitrobenzoic acid catalyzed with poly(1-methyl-3-allylimidazolium bromide) (IIa), poly[l-methyl-3-(2-propinyl)imidazolium chloride] (IIb) and poly[l-methyl-3-(2-methacryloyloxyethyl)imidazolium bromide] (IIc) in a 28.5% aqueous ethanol was investigated as a function of pH and compared with low-molecular weight models, viz., l-methyl-3-alkylimidazolium bromides (the alkyl group being methyl, propyl, and hexyl, resp). Polymers IIb, IIc possessed a higher activity at pH above 9, while the models were more active at a lower pH with a maximum at pH 7.67. The catalytic activity at the higher pH is attributed to an attack by the OH- group, while at the lower pH it is assigned to a direct attack of water on the substrate. The rate of hydrolysis of 4-acetoxy-3-nitrobenzoic acid is proportional to the catalyst concentration [IIc] and proceeds as a first-order reaction. The hydrolysis depends on the composition of the solvent and was highest at 28.5% (vol.) of ethanol in water. The hydrolysis of a neutral ester, 4-nitrophenyl acetate, was not accelerated by IIc.

Benzyl ethers of methyl α-D-glucopyranoside

1980 ◽  
Vol 45 (7) ◽  
pp. 1959-1963 ◽  
Author(s):  
Dušan Joniak ◽  
Božena Košíková ◽  
Ludmila Kosáková
Keyword(s):  
Kinetic Study ◽  
Spectrophotometric Determination ◽  
Reductive Cleavage ◽  
Ether Bond ◽  
Benzyl Ethers ◽  
Acid Catalyzed ◽  
Model Substances ◽  
Hydrolysis Of

Methyl 4-O-(3-methoxy-4-hydroxybenzyl) and methyl 4-O-(3,5-dimethoxy-4-hydroxybenzyl)-α-D-glucopyranoside and their 6-O-isomers were prepared as model substances for the ether lignin-saccharide bond by reductive cleavage of corresponding 4,6-O-benzylidene derivatives. Kinetic study of acid-catalyzed hydrolysis of the compounds prepared was carried out by spectrophotometric determination of the benzyl alcoholic groups set free, after their reaction with quinonemonochloroimide, and it showed the low stability of the p-hydroxybenzyl ether bond.

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