Oxidation studies on some natural monoterpenes: Citral, pulegone, and camphene

Citral extracted from Cymbopogon citratus (Gramineae) was subjected to photochemical epoxidation with hydrogen peroxide to obtain a mixture of epoxy derivatives at the C²=C³ and C⁶=C⁷ double bonds. The thermal oxidation of citral with m-chloroperoxybenzoic acid at room temperature gave only the corresponding 6,7-epoxy derivative as a mixture of E and Z isomers with respect to the C²=C³ double bond. Photosensitized oxygenation of citral in the presence of tetraphenylporphyrin, Rose Bengal, or chlorophyll lead to a mixture of two isomeric hydroperoxides, (2E)-6-hydroperoxy-3,7-dimethylocta-2,7-dienal and (2E,5E)-7-hydroperoxy-3,7-dimethylocta-2,5-dienal. Epoxidation of pulegone isolated from Penny royal oil (Mentha pulegium, Lamiaceae) with hydrogen peroxide under irradiation with a sodium lamp lead to a mixture of cis- and trans-isomeric 2,2,6-trimethyl-1-oxaspiro[2.5]octan-4-ones, whereas under conditions of photosensitized oxygenation two hydroperoxide derivatives, 2-(1-hydroperoxy-1-methylethyl)-5-methylcyclohex-2-en-1-one and 2-hydroperoxy-5-methyl-2-(1-methylethenyl)cyclohexan-1-one, were also formed. Camphene reacted with hydrogen peroxide under irradiation to give a mixture of the corresponding endo- and exo-epoxy derivatives and camphor, while its thermal oxidation with m-chloroperoxybenzoic produced only the two former. Published in Russian in Zhurnal Organicheskoi Khimii, 2008, Vol. 44, No. 6, pp. 825–833. The text was submitted by the authors in English.     

Abrupt rise of the longitudinal recoil ion momentum distribution for ionizing collisions

We report on the experimental observation of an abrupt rise in the longitudinal momentum distribution of recoil ions created in proton helium collision. The details of this structure can be related to electrons traveling with the velocity of the projectile [electron capture to the continuum (ECC)]. The longitudinal as well as the transverse distribution of the recoil ions can be explained as a continuation of the momentum distribution from ions resulting from electron capture illustrating the smooth transition from the capture to bound states of the projectile to the ECC.     

Photosynthesis of dimeric cinnamaldehyde,eugenol, and safrole as antimicrobial agents

It has been reported that trans-cinnamaldehyde, eugenol and safrole inhibited bacteria and fungi growth in vivo mode. In order to improve their biological activity, dimeric cinnamaldehyde, eugenol and safrole have been photosynthesized. The photosynthesis compounds were 4,6-diphenyl-1,2-dioxane-3,5-dicarboxaldehyde, 4,4-(cyclobutone-1,3-diyl bis(methylene))bis(2-methoxyphenal), and 3,6-bis(benzo[d][1,3]dioxol-5-ylmethyl)-1,2-dioxane. These new dimeric compounds strongly inhibited Candida albicans growth more than the monomers.