Llewellyn H Welsh

Bio: Llewellyn H Welsh is an academic researcher from Food and Drug Administration. The author has contributed to research in topics: Acetic anhydride & Epinephrine. The author has an hindex of 5, co-authored 16 publications receiving 199 citations.

The analysis of solutions of epinephrine and norepinephrine

Abstract: A method of analysis is described which is applicable to solutions of epinephrine and norepinephrine, such as epinephrine injection U. S. P. and levarterenol bitartrate injection N. N. R. The method depends on the quantitative conversion of the substances into O3, O4, N‐triacetyl derivatives which may be extracted into chloroform, weighed, identified, and examined polarimetrically for the determination of stereo‐chemical composition. Excellent recoveries of the physiologically potent l‐isomer are obtained, and results of analyses of solutions of epinephrine show very good agreement with potencies determined by the U. S. P. XIV dog bioassay. By supplementing the method with partition chromatography of the acetylation product, the norepinephrine in a solution of U. S. P. epinephrine may be quantitatively isolated as its triacetyl derivative and determined colorimetrically after deacetylation and oxidation to noradrenochrome.

Pseudoephedrine as a Practical Chiral Auxiliary for the Synthesis of Highly Enantiomerically Enriched Carboxylic Acids, Alcohols, Aldehydes, and Ketones

Abstract: The use of pseudoephedrine as a practical chiral auxiliary for asymmetric synthesis is described in full. Both enantiomers of pseudoephedrine are inexpensive commodity chemicals and can be N-acylated in high yields to form tertiary amides. In the presence of lithium chloride, the enolates of the corresponding pseudoephedrine amides undergo highly diastereoselective alkylations with a wide range of alkyl halides to afford α-substituted products in high yields. These products can then be transformed in a single operation into highly enantiomerically enriched carboxylic acids, alcohols, aldehydes, and ketones.

Ephedra in perspective--a current review.

Abstract: Although the traditional use of Ephedra 'ma huang' has been established for thousands of years, its resurgence in the US as a herbal dietary supplement is currently a matter of national controversy. At the heart of the debate are three important questions: (1) the identity and composition of Ephedra products with regard to ephedrine and related alkaloids; (2) the potential therapeutic utility of Ephedra supplements for weight loss or performance enhancement; and (3) potential health risks associated with such uses of Ephedra, particularly in sensitive individuals or in cases of intentional abuse for its stimulant properties. This review surveys the literature on Ephedra with regard to traditional uses, botany, chemistry, analytics, pharmacological effects and health risks. A brief discussion of the central issues in the current debate on the regulation of Ephedra in the United States is included as this is where most of the problems have occurred to date.

Identification of a pheromone blend attractive to Manduca sexta (L.) males in a wind tunnel

Abstract: Analyses of solvent rinses of the external surfaces of pheromone glands excised from calling female tobacco hornworm moths, Manduca sexta (L.), revealed the presence of the following compounds: (Z)-9-hexadecenal, (Z)-11-hexadecenal, (E)-11-hexadecenal, hexadecanal, (E,Z)-10,12-hexadecadienal, (E,E)-10,12-hexadecadienal, (E,E,Z)-10,12,14-hexadecatrienal, (E,E,E,)-10,12,14-hexadecatrienal, (Z)-11-octadecenal, (Z)-13-octadecenal, octadecanal, and (Z,Z)-11,13-octadecadienal. The two trienals were identified by mass and PMR spectral analyses and by ozonolyses, and their structures were confirmed by synthesis. In a wind tunnel male tobacco hornworm moths exhibit the same behaviors in response to a synthetic blend of all of the components, the gland rinse, or a calling female. Both (E,Z)-10,12-hexadecadienal and (E,E,Z)-10,12,14-hexadecatrienal are required to stimulate males to complete the characteristic behavioral sequence: anemotaxis, approaching and touching the pheromone source, and bending their abdomens in apparent copulatory attempts. The other components of the blend may play more subtle roles.