Displacement affinity chromatography of protein phosphatase one (PP1) complexes

Background  

Protein phosphatase one (PP1) is a ubiquitously expressed, highly conserved protein phosphatase that dephosphorylates target protein serine and threonine residues. PP1 is localized to its site of action by interacting with targeting or regulatory proteins, a majority of which contains a primary docking site referred to as the RVXF/W motif.     

Chemo- and regioselective cyclohydrocarbonylation of alpha-keto alkynes catalyzed by a zwitterionic rhodium complex and triphenyl phosphite

alpha-Keto alkynes react with CO and H(2) in the presence of catalytic quantities of the zwitterionic rhodium complex (eta(6)-C(6)H(5)BPh(3))(-)Rh(+)(1,5-COD) and triphenyl phosphite affording either the 2-, 2(3H)-, or 2(5H)-furanones in 61-93% yields. The cyclohydrocarbonylation is readily accomplished using substrates containing alkyl, aryl, vinyl, and alkoxy groups at the acetylenic terminal, as well as a variety of primary, secondary, and tertiary alkyl, aryl, and heteroaryl groups connected to the ketone functionality. Structural and electronic properties present in the starting materials mediate the chemo- and regioselectivity of the reaction.     

Design, synthesis, and characterization of a series of cytochrome P(450) 3A-activated prodrugs (HepDirect prodrugs) useful for targeting phosph(on)ate-based drugs to the liver

A new class of phosphate and phosphonate prodrugs, called HepDirect prodrugs, is described that combines properties of rapid liver cleavage with high plasma and tissue stability to achieve increased drug levels in the liver. The prodrugs are substituted cyclic 1,3-propanyl esters designed to undergo an oxidative cleavage reaction catalyzed by a cytochrome P(450) (CYP) expressed predominantly in the liver. Reported herein is the discovery of a prodrug series containing an aryl substituent at C4 and its use for the delivery of nucleoside-based drugs to the liver. Prodrugs of 5'-monophosphates of vidarabine, lamivudine (3TC), and cytarabine as well as the phosphonic acid adefovir were shown to cleave following exposure to liver homogenates and exhibit good stability in blood and other tissues. Prodrug cleavage required the presence of the aryl group in the cis-configuration, but was relatively independent of the nucleoside and absolute stereochemistry at C4. Mechanistic studies suggested that prodrug cleavage proceeded via an initial CYP3A-catalyzed oxidation to an intermediate ring-opened monoacid, which subsequently was converted to the phosph(on)ate and an aryl vinyl ketone by a beta-elimination reaction. Studies in primary rat hepatocytes and normal rats comparing 3TC and the corresponding HepDirect prodrug demonstrated the ability of these prodrugs to effectively bypass the rate-limiting nucleoside kinase step and produce higher levels of the biologically active nucleoside triphosphate.     

A simple oxidation of formycin to oxoformycin and oxoformycin B. Synthesis of 6-methyloxoformycin,A C-nucleoside analog of doridosine

A simple, high-yield procedure has now been developed for the direct oxidation of formycin to oxoformycin and oxoformycin B. Treatment of formycin (1) with bromine/water provided oxoformycin (8) . A similar treatment of formycin B (4) gave oxoformycin B (6) . Upon prolonged exposure of either 1 or 8 to bromine/water at reflux temperature, conversion to 6 occurred in good yield. Application of this procedure to 1-methylformycin (2) , 1-methylformycin B (5) and 2-methylformycin (17) gave 1-methyloxoformycin (9) , 1-methyloxoformycin B (7) and 2-methyloxoformycin (18) , respectively. Deamination of 8 and 9 with nitrosyl chloride also gave 6 and 7 , respectively. This selective oxidation of 6-methylformycin gave 7-amino-6-methyl-3-β-D-ribofuranosylpyrazolo[4,3-d]pyrimidin-5(4H)-one (10) , a C-nucleoside analog of doridosine. A similar oxidation of 1,6-dimethylformycin B (11) gave 1,6-dimethyloxoformycin B (12) . This direct introduction of the 5-oxo function into the pyrazolo[4,3-d]pyrimidine ring appears to be due to the attack of Br⁺ at N(4), followed by the addition of water to C(5) and subsequent elimination of hydrogen bromide from the transient intermediate 3 .