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Isolation,structure and synthesis of 4-hydroxyisoxazole (triumferol), a seed germination inhibitor from an african plant

The isolation, characterization and an efficient synthesis of 4-hydroxyisoxazole $\text{1}$, a plant growth regulator isolated from an African plant is reported. It is a new compound, which despite the simple structure, had eluded synthesis.     

Problem Department

This department aims to provide problems of varying degrees of difficulty which will interest anyone engaged in the study of mathematics. All readers are invited to propose problems and to solve problems here proposed. Drawings to illustrate the problems should be well done in India ink. Problems and solutions will be credited to their authors. Each solution or proposed problem sent the Editor should have the author's name introducing the problem or solution as on the following pages. The Editor of the Department desires to serve her readers by making it interesting and helpful to them. Address suggestions and problems to Margaret F. Willerding, San Diego State College, San Diego, Calif., 92115 .     

A study of kynurenine fragmentation using electrospray tandem mass spectrometry

A combination of accurate mass measurement and tandem mass spectrometry (both product ion and precursor ion scans) have been used to characterize the major fragment ions observed in the ESI mass spectrum of kynurenine. Kynurenine is a metabolite of tryptophan found in the human lens and is thought to play a role in protecting the retina from UV-induced damage. Three major fragmentation pathways were evident, following initial elimination either of ammonia, H2O and CO or the imine form of glycine. The latter is proposed to occur via the formation of an ion-molecule complex. In the case of loss of H2O and CO from deaminated kynurenine, there is evidence for an acylium ion intermediate, which is not observed for the loss of H2O and CO directly from protonated kynurenine. Product ion scans of deuterated kynurenine enabled the elucidation of structural rearrangements that were not evident in the spectra of the native compound. Since UV filter compounds can often only be isolated in small quantities from the lens, this study forms the basis for the characterization of novel UV filter compounds using mass spectrometry. The approach presented here may also be useful for the characterization of related classes of small molecules.     

A note on a sufficient-decrease criterion for a non-derivative step-length procedure

A step-length algorithm is an essential part of many descent methods for unconstrained and constrained optimization. In this note we present a criterion that defines an acceptable step length when only function values are available at trial step lengths.This research was supported by the U.S. Department of Energy Contract DE-AC03-76SF00326, PA No. DE-AT03-76ER72018; National Science Foundation Grants MCS-7926009 and ECS-8012974; the Office of Naval Research Contract N00014-75-C-0267; and the U.S. Army Research Office Contract DAAG29-79-C-0110.