Synthesis of 1,4-benzodiazepine-1-carbothioamides,bicyclic analogues of the TIBO-type anti-HIV agents

A series of N'-substituted 1,4 -benzodiazepine-1-carbothioamides 2a-j were prepared by reacting the precursor 1,4-benzodiazepine 11 with the corresponding N-substituted isothiocyanates 2a-i or with sodium thiocyanate-trifluoroacetic acid (2j) . Despite the structural ressemblance of these molecules with the potent TIBO-type anti-HIV compound R82150, 2a-j displayed no anti-HIV activity in vitro.     

Arsenic speciation in clams of British Columbia

The water-soluble arsenic compounds in five species of clams – Butter clam (Saxidomus giganteus), Horse clam (Schizothoerus nuttalli), Soft-shelled clam (Mya arenaria), Native littleneck clam (Protothaca staminea), and Manila clam (Venerupis japonica) – are described. Varying amounts of arsenobetaine and tetramethylarsonium ion are the major arsenicals found in all species. Butter clams show the presence of a third compound which appears to be trimethylarsine oxide. Small amounts of as-yet-unidentified arsenicals can also be isolated.     

Algorithms for computing shape preserving spline approximations to data

Summary We treat the problem of approximating data that are sampled with error from a function known to be convex and increasing. The approximating function is a polynomial spline with knots at the data points. This paper presents results (analogous to those in [7] and [9]) that describe some approximation properties of polynomial splines and algorithms for determining the existence of a shape-preserving approximant for given data.Formerly of the Graduate Program in Operations Research, NC State University. Author nowResearch supported in part by NASA Grant NAG1-103     

Synthesis of substituted, 2,2,5,5-tetramethylpyrrolidin-l-oxyl spin labels–PH sensitivity studies

The synthesis of derivatives of 2,2,5,5-tetramethylpyrrolidine nitroxide spin labels as pH sensitive probes is reported. The data on the pH sensitivity studies of these compounds indicate that the amino group increases the pH sensitivity of a nitroxide to a greater degree than a cyano, carboxyl or amido group.     

Toward a synthetically useful stereoselective C-H amination of hydrocarbons

Reaction between a sulfur(VI) compound and an iodine(III) oxidant in the presence of a catalytic quantity (<=3 mol %) of a rhodium(II) catalyst leads to the formation of a chiral metallanitrene of unprecedented reactivity. The latter allows intermolecular C-H amination to proceed in very high yields up to 92% and excellent diastereoselectivities up to 99% with C-H bond containing starting materials as the limiting component. The scope of this C-H functionalization includes benzylic and allylic substrates as well as alkanes. Secondary positions react preferentially, but insertion into activated primary C-H bonds or sterically accessible tertiary sites is also possible. Cooperative effects between the nitrene precursor and the chiral catalyst at the origin of these good results have also been applied to kinetic resolution of racemic sulfonimidamide. This methodology paves the way to the use of Csp3-H bonds as synthetic precursors for the introduction of a nitrogen functionality into selected positions.