Synthesis and biological evaluation of phosphatidylinositol phosphate affinity probes.

The synthesis of the complete family of phosphatidylinositol phosphate analogues (PIPs) from five key core intermediates A-E is described. These core compounds were obtained from myo-inositol orthoformate 1 via regioselective DIBAL-H and trimethylaluminium-mediated cleavages and a resolution-protection process using camphor acetals 10. Coupling of cores A-E with phosphoramidites 34 and 38, derived from the requisite protected lipid side chains, afforded the fully-protected PIPs. Removal of the remaining protecting groups was achieved via hydrogenolysis using palladium black or palladium hydroxide on carbon in the presence of sodium bicarbonate to afford the complete family of dipalmitoyl- and amino-PIP analogues 42, 45, 50, 51, 58, 59, 67, 68, 76, 77, 82, 83, 92, 93, 99 and 100. Investigations using affinity probes incorporating these compounds have identified novel proteins involved in the PI3K intracellular signalling network and have allowed a comprehensive proteomic analysis of phosphoinositide interacting proteins.

Synthesis and biological evaluation of a novel cardiolipin affinity matrix.

Cardiolipin (1) is a dimeric phospholipid found in the mitochondrial membranes of both plants and animals. In order to understand better its role, we report the preparation of an immobilised analogue (2) using phosphoramidite chemistry; the probe has been used successfully to bind a recombinant protein containing a cardiolipin-binding domain.

Tetracarboxylate Bis-Bipyridine Ruthenium Dyes: Synthesis, Structural and Electronic Characterisation.

The preparation of ruthenium complexes with novel 2,2'-bipyridine (bpy) ligands bearing four carboxylic acid groups was investigated with a view to creating dyes containing more than two potential anchoring groups per bpy unit for attachment to a titania surface. Synthetic challenges are encountered upon using the 2,2'-bipyridine-3,3',4,4'-tetracarboxylic acid ligand because it readily decarboxylates. The use of the methyl esterified derivative (3) proved to be more successful for complex preparation, with a robust preparation of the [Ru(3)2 Cl2 ] complex identified with diglyme as the solvent. This complex was further converted into the thiocyanato complex, [Ru(3)2 (NCS)2 ], which could not be completely de-esterified. X-ray analysis of crystals obtained from a mixture of isomers for this complex provided data for the S,S- and N,S-coordinated isomers; both showed a twisted arrangement of the pyridine rings in the 2,2'-bipyridine-3,3',4,4'-tetracarboxylic acid ligand, owing to steric hinderance. Conversely, the isosteric 2,2'-bipyridine-4,4',5,5'-tetracarboxylic acid ligand was easily converted into the desired [Ru(2)2 (NCS)2 ] complex through a standard one-pot procedure in N,N-dimethylformamide solvent. All of the complexes presented herein exhibit a significant redshift for the metal to ligand charge-transfer bands, relative to the benchmark ruthenium dye N719 and derivatives thereof. All complexes exhibit a quasi-reversible process for the ruthenium(II/III) couple at approximately 0.4 V versus the ferrocene couple, comparable to analogous ruthenium dyes.

Enantiopure pseudo-C3-symmetric titanium alkoxide with propeller-like chirality.

An enantiopure amine tris(phenolate) ligand containing a single stereogenic center has been used to control the propeller-like chirality of a derived pseudo-C3-symmetric titanium isopropoxide complex with excellent levels of diastereocontrol. [structure: see text].

An (E)-selective synthesis of trisubstituted (E)-alpha,beta-unsaturated acid derivatives.

Potassium alkoxides of N-acyloxazolidin-2-one derived syn-aldolates undergo a novel tandem intramolecular cyclisation elimination reaction to afford trisubstituted (E)-alpha,beta-unsaturated amides in high d.e., which may be converted into their corresponding acids or oxazolines in good yield.

An air stable moisture resistant titanium triflate complex as a Lewis acid catalyst for C-C bond forming reactions.

An air and moisture stable C(3)-symmetric titanium(IV) triflate, supported by a tripodal amine-(tris-phenolate) ligand, has been synthesized and characterized by X-ray crystallography and shown to be a good Lewis acid catalyst for a range of aza-Diels-Alder, Diels-Alder, syn aldol, allylation, and alkylation reactions.

An enantiopure pseudo-C3-symmetric titanium triflate with propeller-like chirality as a catalyst for asymmetric sulfoxidation reactions.

A chiral pseudo-C(3)-symmetric titanium triflate that employs the point chirality of a single stereogenic centre to control the propeller chirality of its aryl rings has been used to catalyse an asymmetric sulfoxidation reaction.

PI(3,4,5)P3 Interactome.

Immobilizing chemically synthesized analogues of PI(3,4,5)P3 onto Affi-10 beads and incorporating them into liposomes allowed their use as affinity absorbents in the comprehensive analysis of the phosphoinositide interactome using cytosolic cell extracts of the LIM1215 colon cancer cell line. This led to the identification of 282 proteins that either interact with PI(3,4,5)P3 or are indirectly captured as part of a complex containing a PI(3,4,5)P3 binding partner. Identification of the proteins was achieved using affinity/LC-MS/MS experiments.