- Novel erythromycin A derivatives: Synthesis of 11,12-benzoxazine ketolides
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A novel series of 11,12-benzoxazine ketolide derivatives of erythromycin A has been synthesized. The C11,C12-benzoxazine structure was constructed stereoselectively through an intramolecular Michael addition of a C12-O-(2-aminophenyl) group to the enone functionality of the 10,11-anhydro erythromycin A derivative 3.
- Zhu, Bin,Maden, Amy,Macielag, Mark J.
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p. 1783 - 1785
(2007/10/03)
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- Synthesis and Adrenergic Activity of Ring-Fluorinated Phenylephrines
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2-Fluoro-, 4-fluoro-, and 6-fluorophenylephrine (6-FPE) were synthesized from the corresponding fluorinated 3-hydroxybenzaldehydes.New routes to 2-fluoro- and 6-fluoro-3-hydroxybenzaldehydes were developed based on regioselective lithiation of 2- and 4-fluorobenzene ortho to fluorine.As with norepinephrine and isoproterenol analogues, the adrenergic properties of phenylephrine were markedly altered by ring fluorination.The order of potency of the fluoro analogues as α1-adrenergic agonists in the stimulation of contraction of aorticstrips and of phosphatidylinositol turnover and potentiation of cyclic AMP accumulation in guinea pig synaptoneurosomes was 6-FPE > PE > 4-FPE > 2-FPE.The same pattern was observed for the displacement of radioligands specific for α1- and α2-adrenergic receptors on brain membranes.The order of potency for the displacement of 3H>dihydroalprenolol, a β-specific adrenergic ligand from brain membranes, was 2-FPE > 4-FPE = PE >> 6-FPE. 6-FPE was much more selective for α-adrenergic receptors compared to β-receptors than was phenylephrine.A rationale for the observed fluorine-induced alterations in potency and selectivity of the FPEs for α- and β-adrenergic systems is presented based on fluorine-induced conformations due to electrostatic repulsion of fluorine and the benzyl hydroxyl group.
- Kirk, Kenneth L.,Olubajo, Olarangbe,Buchhold, Konstantin,Lewandowski, Gail A.,Gusovsky, Fabian,et al.
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p. 1982 - 1988
(2007/10/02)
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