The stereochemistry of dehydrogenation of the primary carbinol group of D-galactose by D-galactose oxidase has been determined. Using D-galactose-6-d and methyl 13-D-galactopyranoside-6-d, it has been established that the reaction involves removal of thepro-S 6-hydrogen atom. This conclusion is based on product analysis, and on the relative impact of the deuterium isotope effect on oxidation rates of substrates having different R : S deuteration patterns. The absolute configurations at C-6 of these substrates have been determined by selective chemical transformations to products of known configuration. The rotational conformation of the 6-carbinol group of D-galactose and its possible relationship to the specificity of the enzyme are discussed, as well as the stereochemistry of reductive deuteration of aldehydo sugar derivatives.On a dktermink la stkrkochirnie de deshydrogknation du groupement carbinol primaire du D-galactose par le D-galactose oxydase. I1 a dtk Btabli, en utilisant le D-galactose-6-d et le mkthyl f3-D-galactopyranoside-6-d, que la rkaction implique le depart de I'atome d'hydrogene-6pro-S. Cette conclusion se base sur le produit d'analyse et sur l'impact relatif de I'effet de I'isotope deuterium sur les vitesses d'oxydation des substrats ayant des modeles diffkrents de deutkration R:S. Les configurations absolues en C-6 de ces substrats ont ktk dkterminees par des transformations chimiques selectives en produits de configuration connue. La conformation rotationnelle des groupements carbinole-6 du D-galactose et sa relation possible avec la sptcificite de I'enzyme sont discutkes, de mdme que la stkrkochimie de deuteration reductive des derivks alddhydo des sucres.

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A hexane extract of the gum of an African plant, Commiphora erythraea Engler (Burseraceae), has larvicidal and repellent activity against the lone star tick, Amblyomma americanum (L.) and the American dog tick, Dermacentor variabilis (Say). Adult deer ticks, Ixodes dammini Spielman, Clifford, Piesman and Corwin, were also repelled by the extract. Concentrations of 0.02 mg/cm 2 of the extract impregnated onto filter paper killed 96.15 (+ 3.56)~o ofA. americanum larvae exposed to it for 24 h. A concentration of 0.16 mg/cm 2 was needed to kill 80.3 ~o ofD. variabilis larvae. The extract was less effective as a larvicide again st A. americanum and D. variabilis than permethrin. Less than 15.5 ~o of A. americanum larvae and adults and D. variabilis and L dammini adults entered and remained for 2 or 3 min on areas of cloth strips treated with the extract at the rate of 0.2 mg/cm 2. However, 73.3 to 83.3 ~o of the ticks tested entered and remained in areas treated with hexane. Permethrin was about 1 or 2 orders of magnitude more effective against A. americanum larvae as a repellent than the extract. R~sum~ Actions toxiques et r~pulsives d'extraits de Commiphora erythraea contre les tiquesUn extrait ~t l'hexane de la gomme de la plante africaine, C. erythraea Engler (Burseraceae) a des

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