Antibiotic YC 73 of Pseudomonas origin. 3. Synthesis of thioformin analogues.
In the earlier paper of this series1}, it was reported that YG 73 (I) of a Pseudomonas origin was a cupric complex of an acidic substance named thioformin (II), which could be synthesized by treating N-methylhydroxylamine with potassium dithioformate. Soon after the structure determination of II, the fact that such a simple thiohydroxamic acid derivative as II possesses significant antimicrobial activity prompted us to synthesize structural analogues of II. The analogues represented in the general formula III were readily prepared by the following methods. R\ yS )N-Cf (III) ho/ \h Method A : Direct thioformylation of N-substituted hydroxylamines with potassium dithioformate.
Lawesson's reagent for direct thionation of hydroxamic acids: Substituent effects on LR reactivity
To explore the generality and scope of direct thionation of hydroxamic acids (HAs), the reaction of various structurally diverse HAs with Lawesson's reagent was investigated. The yield of thiohydroxamic acid (THAs) is poor when HAs possess bulky acyl and/or N-substituents, acidic α-hydrogen atoms, or an N-phenyl ring. THAs yields were correlated with Brown sigma parameter. The relative rates of two subsequent processes k and k were also measured. Correlation was also found for methine proton chemical shifts of N-isopropyl benzothiohydroxamic acids. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:676–684, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20259
Selective etching of InP in NaF solution
Abstract The crossing porous structure of InP has been obtained by electrochemical etching in NaF solutions. The behavior of the periodic oscillation occurs at different potential ranges for the different concentrations of solutions, and it will disappear with the concentration of the solution decreased. The scanning electron microscope (SEM) image shows that the pores have two directions on the surface and are perpendicular to each other. The two directions are assigned to [0 1 1] and [ 0 1 ¯ 1 ], respectively. The SEM image of the cross-section also shows that the two directions are assigned to [1 1 1]B and [ 1 1 ¯ 1 ¯ ]B. Both are due to the selective etching of F− ions. The crossing porous structure of InP is a very promising feature for the three-dimensional structure of III–V compound semiconductors for photonic band gap materials.