Graham Ruecroft

Unexpected stereoselectivity in the cis dihydroxylation of some 2-cyclopentene-1-carboxamides

While 4-substituted-2-cyclopentene-1-carboxylate esters gave no facial selectivity in the cis dihydroxylation of the olefin function with osmium tetroxide/N-methylmorpholine-N-oxide, the corresponding carboxamides unexpectedly gave high diastereoselectivity for the isomer useful for carbocyclic ribofuranosyl nucleosides.

Mechanism of the microsomal demethylation of 1-aryl-3,3-dimethyltriazenes

The metabolism of 1-aryl-3,3-dimethyltriazenes by phenobarbital-induced rat liver microsomes results in the formation of 1-aryl-3-methyltriazenes and formaldehyde. Intermolecular kinetic deuterium isotope effects for the reaction are found to be 1.0 (+/- 0.03) in both Vmax and Vmax/Km, respectively. The intramolecular kinetic deuterium isotope effects in Vmax and Vmax/Km are found to be 4.8 (+/- 0.05). There is no correlation of Vmax or Vmax/Km with calculated ionization potentials of the triazenes. For 3-ethyl-3-methyltriazene comparison of values of Vmax and Vmax/Km for ethyl vs methyl loss give rise to values of 3.68 in Vmax and 2.02 in Vmax/Km. Thus, loss of an ethyl group is favoured. The results are discussed in terms of a mechanism in which the triazene undergoes direct hydrogen atom abstraction to form a carbon centred radical. This radical subsequently forms a hydroxymethyltriazene that collapses to formaldehyde and a monomethyltriazene.

Synthesis of S-cysteinyl, S(N-acetylcysteinyl) and S-glutathionyl conjugates op N-hydroxymethyltriazenes

Abstract The title compounds are made by direct condensation of N -hydroxymethyltriazenes with cysteine, N -acetylcysteine or glutathione in trifluoroacetic acid which acts as both acid catalyst and solvent.

A short, scaleable synthesis of both enantiomers of 2-benzoylsulfanyl-5-phthalimidopentanoic acid from ornithine

Abstract An efficient “one-pot” synthesis of (R)- and (S)-2-bromo-5-phthalimidopentanoic acid from ornithine is described. Subsequent reaction with potassium thiobenzoate affords a concise, scaleable route to (R)- and (S)-enantiomers of 2-benzoylsulfanyl-5-phthalimidopentanoic acid, an intermediate in the synthesis of MMP inhibitors.