The first entirely stereoselective total synthesis of (-)-quinine is reported.

No abstract

Polyamines are ubiquitous organic cations implicated in many physiological processes. Because they are positively charged at physiological pH, carrier-mediated systems are necessary for effective membrane permeation, but the identity of specific polyamine transporter proteins in eukaryotic cells remains unclear. Polyspecific organic cation transporters (OCTs) interact with many natural and xenobiotic monovalent cations and have been reported to transport dicationic compounds, including the short polyamine putrescine. In this study, we used Xenopus oocytes expressing mammalian OCT1 (SLC22A1), OCT2 (SLC22A2) or OCT3 (SLC22A3) to assess binding and transport of longer-chain polyvalent polyamines. In OCT-expressing oocytes, [3H]MPP+ uptake rates were 15– to 35–fold higher than in non-injected oocytes, whereas those for [3H]spermidine increased more modestly above the background, up to 3–fold. This reflected up to 20–fold lower affinity for spermidine than for MPP +; thus, K0.5 for MPP+ was ~50 μM in OCT1, ~170 μM in OCT2, and ~60 μM in OCT3, whereas for spermidine, K0.5 was ~1 mM in OCT1, OCT2 and OCT3. Jmax values for MPP+ and spermidine were within the same range, suggesting that both compounds are transported at a similar turnover rate. To gain further insight into OCT substrate specificity, we screened a selection of structural polyamine analogs for effect on [3H]MPP+ uptake. In general, blocking potency increased with overall hydrophobic character, which indicates that, as for monovalent cations, hydrophobicity is a major requirement for recognition in polyvalent OCT substrates and inhibitors. Our results demonstrate that the natural polyamines are low affinity, but relatively high turnover, substrates for OCTs. The identification of OCTs as polyamine transport systems may contribute to further understanding of the mechanisms involved in polyamine homeostasis, and aid in the design of polyamine-like OCT-targeted drugs.

Either silver trifluoromethanesulfonate or a mixture of gold(I) chloride, silver trifluoromethanesulfonate, and triphenylphosphine catalyze the formation of pyrroles from substituted beta-alkynyl ketones and amines. The reactions proceed by using 5 mol % of catalyst with yields of isolated pyrroles ranging from 13% to 92%. Sixteen examples are used to compare the effectiveness of each catalyst.

Alkaloids alchemy: A synthesis of the Lycopodium alkaloid (+)‐fawcettidine (see structure) has been developed which requires 16 steps from (R)‐(+)‐pulegone as the chiral starting material. Key steps include a platinum(II)‐catalyzed annulation reaction of a functionalized enamide and a one‐pot Ramberg–Bäcklund process.

No abstract

Cyclic enesulfonamides, enecarbamates, or enamides tethered to an alkyne cyclize readily with use of platinum(II) chloride. This reaction generates quaternary-substituted carbon centers within simple spiro-fused or more complex tri- and tetracyclic heterocyclic ring systems. The yields for this process range from 50% to 83%. [reaction: see text].

No abstract