Ring–Chain Tautomerism of Hydroxyketones

1971 ◽  
Vol 49 (23) ◽  
pp. 3799-3806 ◽  
Author(s):  
Josephine E. Whiting ◽  
J. T. Edward
Keyword(s):  
Organic Solvents ◽  
Cyclic Form ◽  
Open Chain ◽  
Chain Form

A study of the u.v., i.r., and n.m.r. spectra of 5-hydroxy-2-pentanone and of 6-hydroxy-2-hexanone has shown that in most organic solvents there is a slight preference for the open-chain form of the hydroxyketone over the cyclic hemiketal. Increase in temperature and in polarity of solvent further favors the open-chain tautomer; in water there was no evidence of any cyclic form.

scholarly journals Specificity of 2-keto-3-deoxygluconate-6-P aldolase for open chain form of 2-keto-3-deoxygluconate-6-P.

1977 ◽  
Vol 252 (10) ◽  
pp. 3486-3492
Author(s):  
C F Midelfort ◽  
R K Gupta ◽  
H P Meloche
Keyword(s):  
Open Chain ◽  
Chain Form

D-APIOSE

1958 ◽  
Vol 36 (3) ◽  
pp. 480-485 ◽  
Author(s):  
P. A. J. Gorin ◽  
A. S. Perlin
Keyword(s):  
Lead Tetraacetate ◽  
Open Chain ◽  
Naturally Occurring ◽  
Chain Form

Naturally-occurring apiose is shown by synthesis to be the D-isomer in the open-chain form. In this synthesis 3-O-benzyl-D-fructose is cyanohydrated and the resulting heptonic lactones are reduced to 3-O-benzyl-2-C-(hydroxymethyl)-D-arabo-hexitol. The latter is oxidized with lead tetraacetate affording 2-O-benzyl-3-C-(hydroxymethyl)-D-glycero-tetrose which, on debenzylation, gives 3-C-(hydroxymethyl)-D-glycero-tetrose (D-apiose).

Structure and Acid Strength of Opianic Acid and Its N-Methyl Oxime

1963 ◽  
Vol 16 (4) ◽  
pp. 709
Author(s):  
BH Korsch ◽  
NV Riggs
Keyword(s):  
Carboxylic Acid ◽  
Equilibrium Mixture ◽  
Acid Strength ◽  
Carboxyl Group ◽  
Open Chain ◽  
C 30 ◽  
Chain Form

In water, undissociated opianic acid exists as an equilibrium mixture containing c. 30% of lactol form (Ia) in equilibrium with open-chain form (IIa); the carboxyl group is therefore a stronger acid by c. 0.5 pK units than the measured value (pK 3.06 � 0.03) indicates. Opianic acid N-methyl oxime exists largely as the classical nitrone carboxylic acid (IIIa) in water, and is slightly weaker (pK 2.6-2.7) than opianic acid. Both compounds exist largely as cyclic forms, (Ia) and (IV), respectively, in chloroform.

2-pyrone-4,6-dicarboxylic acid, a catabolite of gallic acids in Pseudomonas species

1982 ◽  
Vol 152 (3) ◽  
pp. 1154-1162
Author(s):  
P J Kersten ◽  
S Dagley ◽  
J W Whittaker ◽  
D M Arciero ◽  
J D Lipscomb
Keyword(s):  
Dicarboxylic Acid ◽  
Gallic Acid ◽  
Gel Filtration ◽  
Sulfhydryl Group ◽  
Hydrolytic Activity ◽  
Major Product ◽  
Open Chain ◽  
Ring Fission ◽  
Single Subunit ◽  
Chain Form

2-Pyrone-4,6-dicarboxylate hydrolase was purified from 4-hydroxybenzoate-grown Pseudomonas testosteroni. Gel filtration and electrophoretic measurements indicated that the preparation was homogeneous and gave a molecular weight of 37,200 for the single subunit of the enzyme. Hydrolytic activity was dependent upon a functioning sulfhydryl group(s) and was freely reversible; the equilibrium position was dependent upon pH, with equimolar amounts of pyrone and open-chain form present at pH 7.9. Since the hydrolase was strongly induced when the nonfluorescent organisms P. testosteroni and P. acidovorans grew with 4-hydroxybenzoate, it is suggested that 2-pyrone-4,6-dicarboxylate is a normal intermediate in the meta fission degradative pathway of protocatechuate. Laboratory strains of fluorescent pseudomonads did not metabolize 2-pyrone-4,6-dicarboxylate, but a strain of P. putida was isolated from soil that utilized this compound for growth; the hydrolase was then induced, but it was absent from extracts of 4-hydroxybenzoate-grown cells that readily catabolized protocatechuate by ortho fission reactions. 2-Pyrone-4,6-dicarboxylic acid was the major product formed when gallic acid was oxidized by purified protocatechuate 3,4-dioxygenase. Protocatechuate 4,5-dioxygenase gave only the open-chain ring fission product when gallic acid was oxidized, but the enzyme attacked 3-O-methylgallic acid, giving 2-pyrone-4,6-dicarboxylic acid as the major product. Cell suspensions of 4-hydroxybenzoate-grown P. testosteroni readily oxidized 3-O-methylgallate with accumulation of methanol.

Structure of the Lipopolysaccharide Core Region of the Bacteria of the Genus Proteus

2002 ◽  
Vol 55 (2) ◽  
pp. 61 ◽  
Author(s):  
E. Vinogradov ◽  
Z. Sidorczyk ◽  
Y. A. Knirel
Keyword(s):  
Core Region ◽  
Core Structure ◽  
The Other ◽  
Carboxyl Group ◽  
Open Chain ◽  
Covalent Linkage ◽  
The Core ◽  
New Type ◽  
First Time ◽  
Chain Form

The lipopolysaccharide (LPS) core structure was studied in seven rough strains of Proteus and 26 smooth strains belonging to various Proteus O-serogroups. All LPSs share a common heptasaccharide fragment, which includes two Kdo, three Hep, one Glc, and one GalA residue. Core structures differ between strains and within each strain in the presence of a variety of additional monosaccharides and non-sugar substituents. In many strains, the LPS includes a cyclic acetal of GalNAc in the open-chain form, which builds up a new type of linkage between monosaccharides. The covalent linkage of aliphatic polyamines, e.g. putrescine and spermidine, to the LPS was confirmed for the first time and the location of the amines at the carboxyl group of a GalA residue established. Analyses revealed peculiar features of the core structure, which are characteristic of P. mirabilis on one hand and P. vulgaris and P. penneri on the other hand.

Hydropyrimidines. V. Hexahydropyrimidines. The reaction of aldehydes and ketones with 1,3-diaminopropanes

1967 ◽  
Vol 20 (8) ◽  
pp. 1643 ◽  
Author(s):  
RF Evans
Keyword(s):  
Secondary Amine ◽  
Cyclic Structure ◽  
Hydrogen Atoms ◽  
Open Chain ◽  
Butyl Group ◽  
Alkyl Groups ◽  
Aldehydes And Ketones ◽  
Amine Structure ◽  
Chemical Behaviour ◽  
Chain Form

Hexahydropyrimidine and some N-alkylated derivatives have been obtained from the reaction of the corresponding trimethylenediamine or its monoprotonated salt with formaldehyde. A variety of spectroscopic evidence supports a cyclic structure for these compounds in preference to a tautomeric open-chain form. The chemical behaviour of hexahydropyrimidine is explicable in terms of a cyclic di-secondary amine structure. The cyclic structure is destabilized with respect to the open- chain form if the hydrogen atoms attached to C2 of the hexahydropyrimidine ring are replaced by alkyl groups and cannot be detected when, in addition, one of the hydrogen atoms attached to nitrogen is replaced by the bulkier t-butyl group. Hexahydro-2-methylpyrimidine is dehydrogenated to 1,4,5,6- tetrahydro-2-methylpyrimidine on shaking with Adams catalyst and hydrogen under laboratory conditions. Hexahydropyrimidines which are tautomeric mixtures are reduced to the corresponding N-alkyl-1,3- diaminopropanes, while those possessing cyclic structures are inert.

STUDIES ON REACTIONS RELATING TO CARBOHYDRATES AND POLYSACCHARIDES: XLIV. SYNTHESIS OF ISOMERIC BICYCLIC ACETAL ETHERS

1933 ◽  
Vol 8 (2) ◽  
pp. 129-136 ◽  
Author(s):  
Earland G. Hallonquist ◽  
Harold Hibbert
Keyword(s):  
Organic Solvents ◽  
Potassium Hydroxide ◽  
New Method ◽  
Vapor Pressures ◽  
Open Chain ◽  
Cyclic Acetals ◽  
Aqueous Potassium Hydroxide ◽  
High Vapor

Two isomeric bicyclic acetal ethers, namely, 3, 5, 7-trioxabicyclo [2, 2, 2] octane and 3, 6, 8-trioxabicyclo [3, 2, 1] octane, have been synthesized by the action of aqueous potassium hydroxide on 1, 3-bromoethylidene glycerol 2-benzoate and 1, 2-bromoethylidene glycerol 3-benzoate respectively. Both isomers are crystalline products possessing similar solubilities in organic solvents and high vapor pressures. They show no indication of interconvertibility on solution in solvents, or under the influence of heat. On hydrolysis they yield glycollic aldehyde and glycerol.A new method for the synthesis of cyclic acetals from simple open-chain acetals is described.

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