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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… (More)
The total synthesis of cladoniamide G, a cytotoxic compound against MCF-7 breast cancer cells (10 μg/mL), was accomplished. Key steps in the sequence include oxidative dimerization of 3-acetoxy-5-chloroindole and a tandem process incorporating three steps: bimolecular carbonyl addition, lactam formation, and carbamate removal.
Synthetic work toward the total synthesis of nitiol has culminated in the construction of two epimeric hydroxylated derivatives, the 1,22-dihydroxynitianes. Key stereodefining steps in the construction of the A-ring fragment (13) were the use of a siloxy-epoxide rearrangement reaction, a Pauson-Khand reaction, a Norrish 1 photochemical cleavage reaction,… (More)
The investigations of a synthetic route incorporating a NBS-promoted semipinacol rearrangement to the 6-azaspiro[4.5]decane fragment within halichlorine ( 1) are presented. A convergent approach was pursued, utilizing two chiral, enantiomerically enriched building blocks, 2-trimethylstannyl piperidene 10 and substituted cyclobutanone 19. Noteworthy… (More)
The first entirely stereoselective total synthesis of (-)-quinine is reported.
Enantioselective catalysis in moderate to excellent yields and ee's has been accomplished using a phosphaalkene-based ligand system. Specifically, the palladium-catalyzed allylic alkylation of 1,3-diphenyl-2-propenyl acetate using a chiral P(sp(2)),N(sp(2)) ligand proceeds with a variety of malonate nucleophiles in 73-95% yield (79-92% ee).
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].
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… (More)
Azaspirocyclic ring systems are present in a variety of alkaloids. Functionalized 1-azaspirocyclopentanones (6, 7, 11, 12) can be efficiently constructed through semipinacol ring expansion reactions of 2-(1-hydroxycyclobutyl)-p-toluenesulfonylenamides (4) promoted by either a Bronsted acid ((S)-(+)-10-camphorsulfonic acid or HCl) or N-bromosuccinimide, an… (More)