- In depth analysis of chiroptical properties of enones derived from abietic acid
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With the use of inexpensive commercially available abietic acid, a whole series of abietane enones were prepared in high yields. The structures of all the products obtained were determined by comprehensive spectroscopic analysis with particular emphasis on the use of advanced NMR techniques, comparison with previously reported data and, where possible, by single crystal X-ray diffraction. However, in cases where X-ray crystallography was not applicable or compounds tested were unstable, a final stereochemical assignment could be inferred only by electronic circular dichroism (ECD) supported by vibrational circular dichroism to increase credibility. To reveal the relationship between structure and chiroptical properties, we used combined experimental and theoretical analysis of geometries, structural parameters, and chiroptical properties of all enones synthesized. A thorough analysis of their conformational flexibility by examining the effect of solvent and temperature on the ECD spectra was also used to achieve desired objectives. As a result, the impact of substituents adjacent to the enone chromophore on the conformation was determined by demonstrating that even slight changes in the position of hydroxyl and isopropyl groups attached to carbon C13 may substantially affect ECD curves' pattern, leading in some cases to Cotton effects sign reversal.
- Masnyk, Marek,Butkiewicz, Aleksandra,Górecki, Marcin,Luboradzki, Roman,Paluch, Piotr,Potrzebowski, Marek J.,Frelek, Jadwiga
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p. 3547 - 3561
(2018/04/14)
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- Dimethylaluminum methyltellurate, a new reagent for the cleavage of hindered methyl esters under exceptionally mild conditions by a novel mechanism
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An efficient and effective new reagent (Me2AlTeMe)2 has been developed for the conversion of methyl esters to the corresponding carboxylic acids in toluene solution at 23°C.
- Reddy, B.V. Subba,Reddy, Leleti Rajender,Corey
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p. 4589 - 4593
(2007/10/03)
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- Sulphonated dehydrogenated sylvate, the preparation and use
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This invention relates to salts of sulfodehydroabietic acid with bismuth or zinc, a kind of new salt useful in treating digestive canal ulcer, acute and chronic gastritis, and erosive gastritis etc., as well as its preparation and use. Said salts can be represented by formula (1), wherein R is Bi(OH)++ or Zn++, 2Bio+, 1/2ZnH, n=0-10. The preparation method comprises following steps: (a) sequentially treating the industrial abietic acid calcium salt with acid, base and extracting with organic solvent to give abietic acid with less isomer; (b) reacting said abietic acid with Pd/C to provide dehydroabietic acid, then converting it to pure sulphonic product, namely sulfodehydroabietic acid, via sulphonation and recrystallization; (c) by use of neutralization or salt displacement reaction to convert the sulphonic product of zinc or bismuth salts of sulfodehydroabietic acid. The resultant salts can used to prepare medicine for treating digestive canal ulcer and gastritis.
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Page/Page column 5
(2008/06/13)
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- A new base mediated method for the cleavage of tert-butyl esters
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A new method for the cleavage of tert-butyl esters with NaH in DMF is described.
- Paul, Soumendu,Schmidt, Richard R.
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p. 1107 - 1108
(2007/10/03)
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- Investigation of the Allergenic Principles from Colophony: Autoxidation, Synthesis, and Sensitization
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The autoxidation of abietic acid (1a), levopimaric acid (2a), and dehydroabietic acid (3a) was studied and the compounds 3a as well as (after esterification) 8b, 9b, 10b, 11b (from 1a); 6b (from 2a); and 4b, 5b (from 3a) were isolated for the first time.Some derivatives (6a, 6b, 13b/14b, and 7b) were semi-synthezised.The isolated autoxidation products, the synthetic compounds and some polar fractions of natural colophony were tested for their sensitizing capacity.Compounds 4a, 10b, 16, and 18 as well as the combined polar fraction A-D of colophony show enhanced sensitizing capacity.Methylation of the acids to the ester significantly reduces their activity.Key Words: Resin acids, autoxidation of / Colophony, allergy of / Sensitizing potency
- Krohn, Karsten,Budianto, Emil,Floerke, Ulrich,Hausen, Bjoern M.
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p. 911 - 920
(2007/10/02)
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