Five-membered ring spiro-annulation via thermal rearrangement of enol silyl ethers of 2-(cyclopropylmethylene)cycloalkanones. A formal total synthesis of some spirovetivane-type sesquiterpenoids

1983 ◽  
Vol 61 (2) ◽  
pp. 288-297 ◽  
Author(s):  
Edward Piers ◽  
Cheuk Kun Lau ◽  
Isao Nagakura
Keyword(s):  
Total Synthesis ◽  
Acid Hydrolysis ◽  
Pyridinium Chlorochromate ◽  
Thermal Rearrangement ◽  
Similar Sequence ◽  
Silyl Ethers ◽  
Tertiary Alcohols ◽  
Enolate Anion ◽  
Enol Silyl Ethers ◽  
Hydrolysis Of

Treatment of the 2-(iodomethylene)cycloalkanones 10 and 11 with lithium (phenylthio)(cyclopropyl)cuprate provided good yields of the corresponding β-cyclopropyl enones 12 and 13, respectively. Thermolysis of the latter substances produced relatively poor yields of the desired spiro-annulation products 14 and 15. However, conversion of 12 and 13 into the corresponding enol silyl ethers 24 and 25, followed by thermal rearrangement of the latter materials and acid hydrolysis of the resulting products, provided synthetically useful yields of the spiro enones 14 and 15. Cuprous iodide-catalyzed addition of methyl magnesium iodide to 2-cyclohexen-1-one, followed by trapping of the resultant enolate anion with cyclopropanecarboxaldehyde, provided the ketols 38, which could be converted readily into the mixture of enol silyl ethers 34 and 35. Thermal rearrangement of the latter substances gave, after acid hydrolysis of the crude thermolysate, the spiro enones 42 and 43 in a ratio of ~2.5:1 (57% yield). Treatment of 42 with methyllithium in ether gave the tertiary alcohols 44 and 45 (ratio ~4:1). Hydroboration (disiamylborane, tetrahydrofuran; H2O2, NaOH) of 44, followed by oxidation of the resultant diol 46 with pyridinium chlorochromate, provided the ketol 47. A similar sequence of reactions converted the olefinic alcohol 45 into the ketol 49. Dehydration (p-toluenesulfonic acid in benzene) of 47 gave the spiro enones 28 and 48, in a ratio of ~9:1. Compound 28, also prepared previously from the ketol 49, had been converted earlier into the spirovetivane-type sesquiterpenoids (±)-α-vetispirene (29), (±)-β-vetivone (30), (±)-hinesol (31), (±)-hinesol acetate (32), and (±)-agarospirol (33).

Thermal rearrangement of functionalized 1,2-divinylcyclopropane systems. A convenient synthesis of substituted 4-cyclohepten-1-ones

1986 ◽  
Vol 64 (1) ◽  
pp. 180-187 ◽  
Author(s):  
Edward Piers ◽  
Max S. Burmeister ◽  
Hans-Ulrich Reissig
Keyword(s):  
Acid Hydrolysis ◽  
The Other ◽  
Thermal Rearrangement ◽  
Enol Ethers ◽  
Acyl Chlorides ◽  
Silyl Ethers ◽  
Convenient Synthesis ◽  
Enol Silyl Ethers ◽  
Hydrolysis Of ◽  
Subsequent Acid

Reaction of the acyl chlorides 14–21 with lithium (phenylthio)(cis-2-vinylcyclopropyl)cuprate (2) provided the ketones 22–29. Compounds 22–25, upon treatment with i-Pr2NLi-Me3SiCl, were converted cleanly into the enol silyl ethers 30–33, which gave the 1,4-cycloheptadienes 34–37 upon thermolysis (100–110 °C). Acid hydrolysis of the latter materials produced the corresponding 4-cyclohepten-1-ones 38–41. However, subjection of the cis-2-vinylcyclopropyl ketones 26–29 to i-Pr2NLi-t-BuMe2SiCl afforded, in each case, a mixture of isomeric enol ethers (26 → 42 + 44 (1:1); 27 → 43 + 45 (1:9); 28 → 56 + 58 (1:1); 29 → 57 + 59 (4:1)). Thermolysis (150–175 °C) of these mixtures, followed by acid hydrolysis of the resultant products, gave the 4-cyclohepten-1-ones 54, 55, 64, and 65, admixed with the corresponding 3-methylenecyclopentenes 52, 53, 62, and 63. On the other hand, treatment of the trans-2-vinylcyclopropyl ketones 70–74 with i-Pr2NLi–t-BuMe2SiCl provided exclusively or predominantly the enol ethers 75–79. Thermolysis (230 °C) of the latter materials and subsequent acid hydrolysis of the resultant products 80, 50, 51, 60, and 61 afforded the 4-cyclopenten-1-ones 38, 54, 55, 64, and 65.

Synthesis of functionalized bicyclo[3.2.1]octa-2,6-dienes by thermal rearrangement of substituted 6-exo-(1-alkenyl)bicyclo[3.1.0]hex-2-ene systems

1987 ◽  
Vol 65 (3) ◽  
pp. 670-682 ◽  
Author(s):  
Edward Piers ◽  
Grace L. Jung ◽  
Edward H. Ruediger
Keyword(s):  
Acid Hydrolysis ◽  
The Other ◽  
Silyl Ether ◽  
Thermal Rearrangement ◽  
Enol Ether ◽  
Silyl Ethers ◽  
Keto Esters ◽  
Other Hand ◽  
Enol Silyl Ethers ◽  
Hydrolysis Of

Thermolysis of each of the enol silyl ethers 31–35 affords, cleanly and efficiently, the bicyclo[3.2.1]octadienes 36–40, respectively. Similarly, thermal rearrangement of the enol silyl ether 50 provides the diene 51. Hydrolysis of 36, 37, and 39, and decarbomethoxylation of the resultant keto esters 41, 42, and 44, gives the ketones 46–48, respectively. The ketone 46 is also obtained by acid hydrolysis of 51. Conversion of 6-methyl-1-hepten-4-yn-3-ol (56) into the enol ether 63 is described. Thermolysis of 63 gives 64, which, upon acid hydrolysis, affords 65. Thermolysis of the enones 68 and 69 produces the bicyclic dienones 70 and 71, respectively. On the other hand, thermolysis of 73 and 74, derived from the enone 69, provides the C-8 exo substituted bicyclo[3.2.1]octa-2,6-dienes 75 and 76, which are transformed smoothly, by acid hydrolysis, into the ketones 77 and 78, respectively.

THE ACID HYDROLYSIS OF GLYCOSIDES: I. GENERAL CONDITIONS AND THE EFFECT OF THE NATURE OF THE AGLYCONE

1964 ◽  
Vol 42 (6) ◽  
pp. 1456-1472 ◽  
Author(s):  
T. E. Timell
Keyword(s):  
Acid Hydrolysis ◽  
Equilibrium Concentration ◽  
Rate Coefficients ◽  
Acidity Function ◽  
Tertiary Alcohols ◽  
Conjugate Acid ◽  
Rate Of Hydrolysis ◽  
Acid Catalyzed ◽  
Opposing Effects ◽  
Hydrolysis Of

First-order rate coefficients and energies and entropies of activation have been determined for the acid-catalyzed hydrolysis of a number of methyl D-glycopyranosides and disaccharides. The relation between the logarithm of the rate coefficients and values for Hammett's acidity function was linear, although different for different acids. All compounds had entropies of activation indicating a unimolecular reaction mechanism. Glucosides of tertiary alcohols were hydrolyzed very rapidly, triethylmethyl β-D-glucopyranoside, for example, 30,000 times taster than the corresponding methyl compound.Increase in size of the aglycone caused a slight increase in the rate of hydrolysis of β-D-glucopyranosides, steric hindrance thus being of no significance. Electron-attracting substituents in the aglycone had little or no influence on the rate of hydrolysis, obviously because they would tend to lower the equilibrium concentration of the conjugate acid, while facilitating the subsequent heterolysis, the two opposing effects more or less cancelling out. These results were discussed in connection with recent studies on the acid hydrolysis of various phenyl glycopyranosides and with reference to the postulated occurrence of an activating inductive effect in oligo- and poly-saccharides containing carboxyl or other electronegative groups at C-5. It was concluded that there is little evidence for the existence of any such effect and that, for example, pseudoaldobiouronic acids should be hydrolyzed at the same rate as corresponding neutral disaccharides.

An efficient catalyst-free Mukaiyama-aldol reaction of fluorinated enol silyl ethers with tryptanthrin

2015 ◽  
Vol 13 (33) ◽  
pp. 8906-8911 ◽  
Author(s):  
Fu-Min Liao ◽  
Yun-Lin Liu ◽  
Jin-Sheng Yu ◽  
Feng Zhou ◽  
Jian Zhou
Keyword(s):  
Total Synthesis ◽  
Natural Product ◽  
Aldol Reaction ◽  
Efficient Catalyst ◽  
Silyl Ethers ◽  
Mukaiyama Aldol Reaction ◽  
Catalyst Free ◽  
Mukaiyama Aldol ◽  
Enol Silyl Ethers ◽  
Fluoroalkyl Group

We report an efficient Mukaiyama-aldol reaction of tryptanthrin with fluorinated enol silyl ethers, which is carried out in methanol without the use of any catalyst. This represents the first modification of tryptanthrin by a fluoroalkyl group, which is applied to the total synthesis of the difluoro analogues of the natural product Phaitanthrin B.

Studies on Reactivity of Pyridinium Chlorochromate — Iodine System: An Efficient Method for Converting Enol Silyl Ethers into α-Iodo Ketones

1982 ◽  
Vol 12 (14) ◽  
pp. 1127-1138 ◽  
Author(s):  
Maurizio D'auria ◽  
Franco D'onofrio ◽  
Giovanni Piancatelli ◽  
Arrigo Scettri
Keyword(s):  
Efficient Method ◽  
Pyridinium Chlorochromate ◽  
Silyl Ethers ◽  
Enol Silyl Ethers

Synthesis of N4-Amino and N4-Hydroxy Derivatives of 5-Azacytidine. A Facile Rearrangement of the N4-Amino Derivative to 5-(3-β-D-Ribofuranosylureido)-1H-1,2,4-triazole

2004 ◽  
Vol 69 (4) ◽  
pp. 905-917 ◽  
Author(s):  
Alois Pískala ◽  
Naeem B. Hanna ◽  
Milena Masojídková ◽  
Pavel Fiedler ◽  
Ivan Votruba
Keyword(s):  
Acid Hydrolysis ◽  
Alkaline Hydrolysis ◽  
Hydroxylamine Hydrochloride ◽  
Amino Derivative ◽  
Cytostatic Activity ◽  
Thermal Rearrangement ◽  
Water Solutions ◽  
Hydrolysis Of ◽  
Derivatives Of

Treatment of methoxyribosyltriazinone 4 with hydrazine in methanol afforded crude 4-hydrazino-1-β-D-ribofuranosyl-1,3,5-triazin-2(1H)-one (N4-amino-5-azacytidine) (2), which rearranged rapidly to isomeric 5-ribosylureidotriazole 6. The rearrangement proceeds easily also in water solutions of 2. Alkaline hydrolysis of 6 gave a mixture of 5-ureidotriazole 7 and 5-aminotriazole 8. Acid hydrolysis of 6 afforded only 7. This compound was also prepared by thermal rearrangement of 5-amino-1-carbamoyltriazole 9 or on reaction of cyano(formyl)guanidine 10 with hydrazine hydrochloride. Treatment of benzoylated methoxyribosyltriazinone 4a with hydrazine in methanol gave only the rearranged product 6a. Reaction of tribenzoylribosyl isocyanate 12 with aminotriazole 8 gave 1-triazolecarboxamidotribenzoylribose 13, which afforded by methanolysis oxazoloribofuranose 14 and aminotriazole 8. Compound 14 was also obtained by methanolysis of blocked ribosylcarbamate 16. Reaction of methoxyribosyltriazinone 4 with hydroxylamine in methanol afforded 4-hydroxylamino-1-β-D-ribofuranosyl-1,3,5-triazin-2(1H)-one (N4-hydroxy-5-azacytidine) (3), which on the action of excess hydroxylamine yielded 1-cyano-1-hydroxy-5-β-D-ribofuranosylisobiuret (19). Treatment of methoxy-1,3,5-triazinone 18 with a solution of hydroxylamine in methanol gave 4-hydroxylamino-1-methyl-1,3,5-triazin-2(1H)-one (N4-hydroxy-1-methyl-5-azacytosine) (17). Heating of cyano(formyl)guanidine 10 with hydroxylamine hydrochloride in water lead to the formation of triuret (21). The mechanisms of the reactions of methoxyribosyltriazinone 4 with hydrazine and hydroxylamine are discussed. Compounds 2, 6 and 19 exhibited no significant antibacterial or cytostatic activity.

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.

Total synthesis of tetracyclic sesquiterpenoids: (±)-ishwarone

1980 ◽  
Vol 58 (23) ◽  
pp. 2613-2623 ◽  
Author(s):  
Edward Piers ◽  
Tse-Wai Hall
Keyword(s):  
Total Synthesis ◽  
Phase Transfer ◽  
Aqueous Sodium Hydroxide ◽  
Pyridinium Chlorochromate ◽  
Aqueous Sodium ◽  
Standard Methodology ◽  
Propargylic Alcohol ◽  
Crude Product ◽  
Hexamethyl Phosphoramide ◽  
Hydrolysis Of

A stereoselective total synthesis of the racemic modification of the tetracyclic sesquiterpenoid ishwarone (2) is described. Treatment of the known ketal aldehyde 19 with dibromomethylenetriphenylphosphorane gave the dibromo alkene 20, which was transformed efficiently into the propargylic alcohol 21. The latter compound was converted via the intermediates 22–24 into the octalone 12, which in turn was transformed by standard methodology into the corresponding ketal 7. Treatment of 7 with bromoform–aqueous sodium hydroxide in the presence of a phase-transfer catalyst, followed by acid hydrolysis of the resultant crude product, gave the crystalline keto dibromide 27. When a solution of the corresponding ketal 26 in tetrahydrofuran–hexamethyl-phosphoramide containing methyl iodide was treated with tert-butyllithium, the monobromo ketals 28 (58%) and 29 (38%) were formed. Compound 28 was converted by means of conventional reactions into the keto alcohol 32. Attempts to transform the latter substance into (±)-ishwarone (2) proved unsuccessful. When the olefinic ketal 7 was allowed to react with dimethyl diazomalonate in the presence of copper bronze, the diester 44 was produced in good yield. The latter intermediate was converted via standard methodology into the keto dimesylate 47 which, upon reaction with lithium chloride in ether–hexamethylphosphoramide, gave the corresponding dichloride 48. Treatment of 48 with potassium tert-butoxide in tetrahydrofuran resulted in an intramolecular alkylation to provide the tetracyclic keto chloride 50. Reduction of 50 with lithium triethylborohydride in tetrahydrofuran afforded (±)-ishwarol (51) which, upon oxidation with pyridinium chlorochromate in dichloromethane, furnished (±)-ishwarone (2).

Regulation of acid hydrolysis of sucrose in acid lime juice sac cells

1991 ◽  
Vol 81 (1) ◽  
pp. 51-54 ◽  
Author(s):  
Ed Echeverria
Keyword(s):  
Acid Hydrolysis ◽  
Lime Juice ◽  
Acid Lime ◽  
Hydrolysis Of
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