The preparation of some bromodeoxy- and dibromodideoxy-pentonolactones

Treatment of ammonium d-xylonate with hydrogen bromide in acetic acid yields 2,5-dibromo-2,5-dideoxy-d-lyxono-1,4-lactone (2a), whereas similar treatment of potassium d-arabinonate gives 5-bromo-5-deoxy-d-arabinono-1,4-lactone (8a) as the main product. Two isomeric 2,5-dibromo-2,5-dideoxy-1,4-lactones are also formed in minor amounts. Selective hydrogenolysis of 2a affords 5-bromo-2,5-dideoxy-d-threo-pentono-1,4-lactone, while prolonged treatment results in the formation of 3-hydroxypentanoic acid. Similarly, hydrogenolysis of 8a produces a 2,3-dihydroxypentanoic acid together with smaller amounts of 5-deoxy-d-arabinono-1,4-lactone; the latter also results from hydrogenolysis of 5-deoxy-5-iodo-d-arabinono-1,4-lactone with Raney nickel.     

The preparation and some properties of yeast mitochondria

Summary A comparison of the structural and functional integrity of yeast mitochondria prepared by a mechanical disintegration method with that reported for mitochondria prepared by enzyme methods has been made.The mitochondria prepared by mechanical disruption show at least as great a degree of functional integrity as that reported for enzymically prepared mitochondria. This was judged by the substrates oxidised, the rates of these oxidations, the respiratory control and ADP:0 ratios and difference spectra.The respiration of citrate and of ethanol by the mechanically prepared mitochondria has been shown to be stimulated by exogenous NAD; in the case of the latter substrate a degree of respiratory coupling became apparent as a consequence of this stimulation.The penetration of NADH₂, and of citrate or of ethanol in the presence of exogenous NAD, into the mitochondria has been examined.The results are consistent with the reported existence of a NADH₂ dehydrogenase system located in the outer area of the inner mitochondrial membrane. The NAD stimulation of ethanol respiration also suggests the occurrence of an external alcohol dehydrogenase in the mitochondrial preparation; similar results with citrate suggest external forms of aconitic hydratase and isocitric dehydrogenase to be present.Unlike animal mitochondria the rate of penetration of oxidisable substrates in uninhibited suspensions appeared to exceed respiration and/or outward diffusion rates in this preparation.Evidence of a malate stimulated citrate and isocitrate transport system similar to that reported for animal mitochondria is presented, but the specificity of the system for tricarboxylate anion appears to differ, at least in respect of propane 1.2.3 tricarboxylate (tricarbalyllate).     

The preparation and study of some novel glycosides of D-galactose

The tert-butyl- and the 2,2,2-trichloroethyl α- and β-D-galactopyranosides were prepared and both α-D-glycosides were selectively benzoylated to give the 2,3,6-tri-O-benzoyl-D-galactopyranosides. Cleaving of the glycosidic groups is described. The glycosides are useful intermediates for oligosaccharide synthesis where generation of a reducing sugar terminus under mild conditions is necessary.     

The preparation and some physical properties of ten methyl dithiastearate isomers

Ten methyl dithiastearate isomers, containing 0-4 methylene groups between the two sulfur atoms in each of the molecules, were synthesized using a one-pot synthesis approach. The preparation of the tetra-methylene (3,4), tri-methylene (5,6) and di-methylene (7,8) interrupted methyl dithiastearate isomers involved the asymmetric coupling of n-bromoalkanes, alkanedithiols and omega-bromoalkanoic acids. The mono-methylene interrupted isomers (9,10) were prepared from dibromethane, which was allowed to couple with n-alkanethiols and omega-mercaptoalkanoic acids. For the non-methylene interrupted isomers (11,12), n-alkanethiols were initially converted to the sulfenyl bromide and reacted with omega-mercaptoalkanoic acids. These sulfur-containing fatty ester analogues were found to be more polar and with longer retention times than methyl stearate when analyzed by TLC (silica) and GC (SE-30) respectively. In the 1H-NMR analysis the shifts of the protons of CH2 groups adjacent to the sulfur atoms in 3-6 appeared at 2.50-2.60 (t) delta, while the tri-methylene interrupted isomers (5,6) furnished an additional characteristic signal at 1.84 (quintet) delta arising from the protons of the beta-positioned CH2 between the sulfur atoms. Compounds 7-8 gave a singlet at 2.70 delta, while 9,10 also gave a singlet at 3.64-3.65 delta for the protons of the CH2 group situated between the sulfur atoms. In compounds 11,12 the shift of the protons of the CH2 adjacent to the sulfur atom appeared at 2.68 (t) delta.(ABSTRACT TRUNCATED AT 250 WORDS)