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At least 1,243 records · Page 69Linked to original sources
PubMed1975

Acylation of ascorbic acid in water.

The acylation of ascorbic acid by acetic anhydride was studied in water at 25 degrees. The results indicate that the initial products of reactions between these two compounds were acetic acid and 3-o-acetylascorbic acid. The latter product then underwent two parallel reactions: hydrolysis to ascorbic and acetic acids and an intramolecular O leads to O acyl migration to yield-O-acetylascorbic acid. The former reaction was predominant at pH values below 4, whereas the latter reaction predominated at pH values between 4 and 7. These results are used as a basis for questioning the structural assignments previously made to some ascorbic acid esters.

Acetylation↗
PubMed1987

Cardiovascular differences between phenylpropanolamine and its related norephedrine isomers in the rat.

Various studies have confused the norephedrine and norpseudoephedrine isomers with phenylpropanolamine (PPA, d,l-norephedrine). This confusion has led us to investigate the pharmacological activity of the norephedrine (NOR) and norpseudoephedrine (NORP) isomers in the cardiovascular system of the urethane:chloralose anesthetized rat. Following intravenous administration, in a cumulative-dose fashion, l-NOR and PPA were the most potent compounds at increasing arterial blood pressure, while d-NOR, d-NORP, and l-NORP were relatively inactive at the doses tested (0.31-10 mg/kg). Prior reserpinization did not significantly shift the cumulative dose-response curves for l-NOR and PPA. Repetitive injections of PPA and l-NOR (1 mg/kg, 4 doses at 5-min intervals) failed to produce tachyphylaxis to the pressor response. On the other hand, when d-NORP was administered in a similar fashion, tachyphylaxis to the second and subsequent doses was observed. These studies demonstrate that significant mechanistic differences exist between these norephedrine isomers.

Animals↗
PubMed1990

Structure of amiprilose hydrochloride, a novel anti-inflammatory agent.

Amiprilose hydrochloride is a carbohydrate-derived, novel anti-inflammatory with potential application in the treatment of rheumatoid arthritis. A spectroscopy-based approach was undertaken to assign both the relative and absolute configuration of its five chiral centers. The fully assigned 13C and 1H NMR spectra of amiprilose hydrochloride was used to establish the relative stereochemistry of four of its five chiral centers held rigid in its furanose ring system. Parallel synthesis of the enantiomer of amiprilose hydrochloride from L-glucose was followed by CD spectropolarimetry to establish that no inversion of chiral centers had occurred in the synthesis. The hydrobromide salt of amiprilose and its enantiomer were prepared and, together with amiprilose hydrochloride, were crystallized. X-ray crystallographic analysis resulted in the assignment of the absolute configuration of all five chiral centers.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

Stability of diltiazem in acid solution.

A brief study of the stability of diltiazem was conducted at 70 degrees C in the pH range of 0.45 to 6.1 using polarimetry. Racemization did not occur. The hydrolysis rate of the acetate ester moiety was found to be slow, with a minimum in the pH-rate catenary at approximately pH 3.5. Where reaction products are known, photoelectric polarimetry has great advantages in speed, convenience, and cost compared with chromatographic methods for measuring rates of reaction of optically active analytes.

Diltiazem↗