Ian D. Entwistle

Rapid catalytic transfer reduction of aromatic nitro compounds to hydroxylamines

Abstract A general method has been developed for the rapid, metal-catalysed transfer reduction of nitro compounds to N-substituted hydroxylamines.

Isolation of a pure toxic polypeptide from the venom of the spider Phoneutria nigriventer and its neurophysiological activity on an insect femur preparation.

The venom of the South American spider Phoneutria nigriventer has been separated into eleven fractions by gel filtration. The neurophysiological activity of each fraction was tested by perfusion of a locust femur preparation. Fractions which gave a neurophysiological response on this perfusion were fractionated further by ion-exchange chromatography. The purity of each sub-fraction was monitored by isoelectrofocusing on polyacrylamide gels and isoelectric points determined. From one of the polypeptide-containing fractions, a pure, almost neutral polypeptide was isolated and shown to have a molecular weight between 5500 and 5900. The amino acid composition of the pure polypeptide was: Ala6,7 Arg2,3 Asx3 Cys8 Glx3 Gly4 Ile4 Leu1 Lys5,6 Phe2 Ser5 Thr3 Trp1 Tyr2 Val2. This polypeptide elicited the greatest neurophysiological activity of all fractions tested. When the polypeptide (2 X 10(-7) M) was perfused through the locust femur preparation, action potentials were generated along the length of the axons in the crural nerve, resulting in very rapid and uncontrolled twitching of the skeletal muscles. At higher concentrations, the crural nerve discharged repetitively, both spontaneously and in response to a single electrical stimulus. The other polypeptide fractions, although less pure, had neurophysiological responses similar to those observed with the pure polypeptide; the effects of some fractions could be reversed. Further fractions of low molecular weight were purified by thin-layer or paper chromatography to give two pure components that are probably nucleosides or nucleotides. After the initial gel filtration of the total venom had separated the high molecular weight proteinases from the polypeptides, all of the polypeptides retained their neurophysiological activity in solution for several days. In the presence of the proteinases, the polypeptides were inactivated in solution in a few hours at room temperature.

Metal-assisted reactions—Part 11: Rapid reduction of N-nitrosoamines to N,N-disubstituted hydrazines; the utility of some low-valent titanium reagents☆

Abstract The rapid reduction of N-nitrosoamines to N,N-disbustituted hydrazines by a low-vanet titanium reagent is described. The reagent is selective in that many other functional groups are unaffected by it. The nature of the low-valent titanium reagent is discussed in terms of experimental results of comparisons of its reactivity and that of other low-valent titanium reducing agents.

Metal-assisted reactions. Part 9. Rapid replacement of phenolic hydroxyl groups by hydrogen.

Abstract Conversion of phenolic ethers to hydrocarbons by catalytic transfer hydrogenation is reported.

Hydrogenolysis of Allyl and Benzyl Halides and Related Compounds

Hydrogenolysis to effect replacement of a group XR attached to a benzylic or allylic center by its heteroatom (X), is widely used in organic synthesis, especially in protecting group strategies, most frequently involving replacement of one group XR, where X is O, N or S (Scheme 1). In reviewing this area of chemistry we have dealt with the material in a functional, rather than an historical, approach, covering first the catalytic methods, then the hydride reducing reagents, followed by dissolving metal reductions. These three sections form the bulk of the review, with other methods, which are less widely employed, examined in less detail at the end.