FORMATION OF CYCLIC O-2′-HYDROXYETHYLIDENE ACETALS FROM POLYALCOHOLS OF 4-O-LINKED POLYSACCHARIDES

1965 ◽  
Vol 43 (11) ◽  
pp. 2978-2984 ◽  
Author(s):  
P. A. J. Gorin ◽  
J. F. T. Spencer
Keyword(s):  
Acid Hydrolysis ◽  
Sodium Periodate ◽  
Rhodotorula Glutinis ◽  
Membered Ring ◽  
The Other ◽  
Complete Oxidation ◽  
Partial Acid Hydrolysis ◽  
Ring Form ◽  
Hydrolysis Of ◽  
By Products

Partial acid hydrolysis of polyalcohols derived from some 1,4-O-linked polysaccharides gave cyclic O-2′-hydroxyethylidene derivatives as by-products in yields of 6–18%. Polysaccharides containing β-links such as Rhodotorula glutinis mannan and cellulose gave rise to 6-membered ring acetals with lesser amounts of the 5-membered ring form. On the other hand, two α-linked polyalcohols, obtained following partial and complete oxidation of starch with sodium periodate, were converted to 5-membered O-2′-hydroxyethylidene acetals.

Phosphopeptides Obtained by Partial Acid Hydrolysis of α-Casein2

1957 ◽  
Vol 79 (10) ◽  
pp. 2559-2565 ◽  
Author(s):  
N. J. Hipp ◽  
M. L. Groves ◽  
T. L. McMeekin
Keyword(s):  
Acid Hydrolysis ◽  
Partial Acid Hydrolysis ◽  
Hydrolysis Of

Phosphanchalkogenide und ihre Metallkomplexe. IV. Halogenierungsprodukte der Gold(I)halogenidkomplexe einiger Diphosphanmonochalkogenide

2016 ◽  
Vol 71 (3) ◽  
pp. 249-265 ◽  
Author(s):  
Christina Taouss ◽  
Peter G. Jones
Keyword(s):  
Membered Ring ◽  
Quantitative Yield ◽  
X Ray Diffraction ◽  
Central Ring ◽  
X Ray ◽  
Hydrolysis Products ◽  
Related Product ◽  
Hydrolysis Of ◽  
By Products

AbstractDiphosphanegold(I) complexes of the form dppmEAuX [dppm = bis(diphenylphosphano)methane, E = S, Se; X = Br, I], dppeEAuX [dppe = 1,2-bis(diphenylphosphano)ethane; E = O, S; X = Br, I] and dppbzEAuX [dppbz = 1,2-bis(diphenylphosphano)benzene; E = S, Se, X = Br, I] were treated with elemental X2. With dppm, the three products [dppmEAuX2]+X3– (E = S, X = Br (1), I (2); E = Se, X = I (3) were obtained in quantitative yield. These are gold(III) complexes involving a five-membered ring . With dppe, the only related product was [dppeEAuBr2]+Br3– (4), in which the central ring is six-membered with two carbon atoms. These dppe systems are very sensitive to oxidation/hydrolysis of the ligand, and several such unintended products were isolated and identified. The reaction of dppbzSAuBr with bromine leads to [dppbzS]2+[AuBr4]–Br– (5), the dication of which is formally 1,1,3,3-tetraphenylbenzo[d]-2-thia-1, 3-diphosphol-1,3-diium and contains a central five-membered ring . The dications are associated with the bromide anions via S…Br contacts of ca. 3.1 Å to form inversion-symmetric S2Br2 rings. The halogenation of the dppbzSe derivatives leads to loss of selenium and formation of dppbzAuBr3 (6), with [4+1] coordination at gold, or the known compound [dppbzAuI2]+I3– (7). All products 1–6 were subjected to X-ray diffraction analyses, as were four hydrolysis products 4a–d and two further by-products [5(thtBr+)·2Br3–·3(AuBr4–)] (1a) and (tht)AuBr3 (1b). Compound 1a displays unusually short Br…Br contacts of 3.2398(8) Å between neighbouring tetrabromidoaurate(III) ions.

REACTIONS OF OXODELCOSINE AND INTERRELATION OF DELCOSINE AND DELSOLINE

1960 ◽  
Vol 38 (12) ◽  
pp. 2433-2440 ◽  
Author(s):  
Vinko Skarić ◽  
Léo Marion
Keyword(s):  
Sodium Borohydride ◽  
Membered Ring ◽  
Lead Tetraacetate ◽  
The Other ◽  
Supporting Evidence ◽  
Close Relationship ◽  
Suggested Structure ◽  
Hydrolysis Of

The oxidation of diacetyldelcosine produces a lactam which, after hydrolysis of the acetyl groups, can be oxidized further to a diketo-lactam in which one of the keto groups is in a five- and the other in a six-membered ring. This result leads to an alteration of the previously suggested structure of delcosine. The new structure suggests a close relationship between delcosine and delsoline which is confirmed by the methylation of the former. The reaction is selective and gives rise to a monomethyldelcosine identical in every way with delsoline. Reduction of the diketo-lactam (didehydro-oxodelcosine) with sodium borohydride gives oxodelcosine. Dehydro-oxodelcosine is also described, and its oxidation with lead tetraacetate as well as that of oxodelcosine lead to the formation of keto-products which lend supporting evidence for the structure assigned to delcosine.

The products of hydrolysis of cyclic orthoesters as a function of pH and the theory of stereoelectronic control

1985 ◽  
Vol 63 (9) ◽  
pp. 2485-2492 ◽  
Author(s):  
Pierre Deslongchamps ◽  
Jean Lessard ◽  
Yves Nadeau
Keyword(s):  
Acid Hydrolysis ◽  
Hydroxy Ester ◽  
The Other ◽  
Relative Percentage ◽  
Stereoelectronic Control ◽  
Hydrolysis Of ◽  
Tetrahedral Intermediates

The acid hydrolysis of cyclic orthoesters 1, 3–6 (R = Me), and 2 (R = Me and Et) as a function of pH was studied. The bicyclic orthoester 5 yields mainly the hydroxy-ester (less than 5% lactone), and this result is essentially independent of pH. For the other orthoesters, the relative percentage of products differs for each case and varies with pH. At pH ≤ 3, the percentage of lactone is always larger than at pH > 3. These results are explained on the basis of the stereoelectronic theory for the cleavage of tetrahedral intermediates.

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.

Acetohydroxy acid reductoisomerase of wheat

2000 ◽  
Vol 27 (5) ◽  
pp. 417 ◽  
Author(s):  
Roberta Donadini ◽  
Les Copeland
Keyword(s):  
Molecular Mass ◽  
Triticum Aestivum L ◽  
The Other ◽  
Size Exclusion ◽  
Elution Volume ◽  
Substrate Preparation ◽  
Strong Base ◽  
High Degree ◽  
Hydrolysis Of ◽  
By Products

Acetohydroxy acid reductoisomerase (EC 1.1.1.86, AHAR) was purified to a high degree from green shoots of wheat (Triticum aestivum L. cv. Vulcan). The enzyme was localised in the chloroplasts, and activity was at a maximum approximately 4 d after germination. The subunit molecular mass of wheat AHAR was 57 kD and activity of the native enzyme had an elution volume from size exclusion columns that corresponded to a molecular mass of 47 kD. The enzyme did not require the addition of Mg 2+ ions to reaction mixtures for activity. The Km values for (R,S)-2-acetolactate and (R,S)-2-aceto-2-hydroxybutyrate were 91 and 9 mM, respectively, and the corresponding maximum velocities were 430 and 451 mU mg –1 protein. The Km for NADPH was approximately 10 mM when either of the acetohydroxy acids was the other substrate. Preparation of the acetohydroxy acid substrates by hydrolysis of the parent esters in strong base led to the formation of inhibitory by-products. Racemisation of the acetohydroxy acids was detected in assay mixtures.

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