Eduardo Palomino

Cosensitized electron transfer photo-oxygenation: The photochemical preparation of 1,2,4-trioxolanes, 1,2-dioxolanes and 1,2,4-dioxazolidines☆

Abstract 9,10-dicyanoanthracene (DCA) sensitizes the electron transfer photo-oxygenation of epoxides, cyclopropanes and aziridines to yield 1,2,4-trioxolanes (ozonides), 1,2-dioxolanes and 1,2,4-dioxazolidines respectively. The addition of biphenyl (BP) as a cosensitizer can provide significantly enhanced rates of reaction of various substrates. An investigation of the stereochemistry of the photo-oxygenation of epoxides and aziridines has given support to a mechanism involving the addition of singlet oxygen as a dipolarophile to intermediate carbonyl and azomethine ylides. A mechanism for DCABP cosensitization is presented.

Binding, X-Ray and NMR studies of the three A-ring isomers of natural estradiol

The effect of the position of the phenolic hydroxyl on the conformations of the three A-ring isomers of estradiol, namely, estra-1,3,5(10)-trien-1,17 beta-diol (10), estra-1,3,5(10)-trien-2,17 beta-diol (3), and estra-1,3,5(10)-trien-4,17 beta-diol (6), has been analyzed by X-ray crystallography. The results of these analyses were correlated with the absorptions of the angular methyl groups in the [1H]NMR spectra of these isomers and natural estradiol (E2). It was observed that the changes in chemical shift of protons at C18 corresponded to skeletal modifications in the steroid structure which changed the anisotropic effect of the hydroxyl group at C17. Examination of the affinity of these A-ring isomers of E2 for the estrogen receptor has shown the 2-hydroxylated isomer 3 to retain 1/5th the affinity of E2 for its binding protein. The 1- and 4-hydroxylated derivatives (10 and 6, respectively) bound to a much lesser extent. The receptor affinities of these estrogen analogues may be related to the angle between the 18-methyl and the 17 beta-hydroxyl groups (or the dihedral angle between the planar A-ring and the angular C18 methyl) as well as the position of the A-ring hydroxyl group.

Strained oxiranes from cis-diols

Abstract Cis-diols of some strained molecules are converted to epoxides without inversion of configuration by the use of the redox system triphenylphosphine : diethylazodicarboxylate, or by treatment of their dimethylaminodioxolane derivatives with trifluoroacetic anhydride as catalyst.

A Dihydropyridine Carrier System for Delivery of 2′,3′-Dideoxycytidine (DDC) to the Brain

Abstract The present study extends the dihdropyridine ⇌ pyridinium salt redox system to the delivery and sustained release of 2′,3′-dideoxycytidine (DDC) to the brains of mice in a continuing search for agents that may prove effective in reversing complicating neurological disorders of AIDS.

Photooxygenation of strained epoxides

Photooxygenation of strained epoxides, type 1, in the presence of DCA or TCA afforded ozonide 2 in different ratios. A mechanism involving trapping of a radical cation by 3O2 is proposed. Trapping of an ylide intermediate by 1O2 is also considered in the DCA-sensitized photooxygenation.