The high level of catalyst performance was attainable in the palladium-catalyzed 1,2-addition of aryl-, heteroaryl-, and alkenylboronic acids to aromatic, heteroaromatic, and aliphatic aldehydes ...using thioether-imidazolinium chloride L5 as a heterobidentate carbene ligand precursor.
Palladium-catalyzed 1,2-addition of potassium aryl- and alkenyltrifluoroborates to aldehydes using thioether-imidazolinium carbene ligands proceeded readily under aqueous conditions. This process ...tolerated a diverse range of potassium trifluoroborate salts and aldehydes, giving a variety of carbinol derivatives with good to excellent yields.
Tropic acid was synthesized in a good yield and with high enantioselectivity (81% ee) under non-biphasic conditions
via
the novel hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone ...(tropic acid β-lactone) in the presence of a chiral quaternary ammonium phase-transfer catalyst and strongly basic anion exchange resin as the hydroxide ion donor.
The hydrolytic dynamic kinetic resolution of racemic 3-phenyl-2-oxetanone using a chiral PTC and water-free basic anion exchange resin as the hydroxide ion donor was achieved.
Direct aldol reactions of several aromatic aldehydes with ketones using
l-proline-2,4,6-trinitroanilide catalyst
2d were conducted. Under optimized conditions, high enantioselectivity (99% ee), ...regioselectivity (up to 95:5), and diastereoselectivity (up to 98:2) were achieved.
We report here on the construction of the ABC-ring framework of (±)-Taxol using an intramolecular aldol reaction as a key step. AB-ring compound
8 was converted to ketoaldehyde
25 as a precursor of ...an aldol reaction via introduction of oxygen-functionalities and a methoxycarbonyl group, which can be converted to a methyl group, in the proper positions of the B-ring. An aldol reaction of ketoaldehyde with LDA led to the formation of the desired product
27, which corresponds to the ABC-ring framework of (±)-Taxol.
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Syntheses of D- and L-myo-inositol 3,4,5,6-tetrakisphosphates were achieved via diastereoselective 1,2-addition of vinylcopper reagent with the chiral aldehyde prepared from ...1,2,5,6-diisopropylidene-D-glucose, ring-closing metathesis of 1,7-diene with Grubbs catalyst followed by catalytic OsO4 dihydroxylation of (+)-conduritol B derivatives.
The synthesis of 3-arylphthalides via palladium-catalyzed arylation of aldehydes with organoboronic acids was achieved using the thioether-imidazolinium carbene ligand in good to excellent yields and ...was carried out using 1.0 mol % of the catalyst with high substrate tolerance.
FKBP52 (HSP56, p59, HBI) is the 59-kDa immunosuppressant FK506-binding protein and has peptidyl prolyl isomerase as well as a chaperone-like activity in vitro. FKBP52 associates with the heat shock ...protein HSP90 and is included in the steroid hormone receptor complexes in vivo. FKBP52 possesses a well conserved phosphorylation site for casein kinase II (CK2) that was previously shown to be associated with HSP90. Here we examined whether FKBP52 is phosphorylated by CK2 both in vivo and in vitro. Recombinant rabbit FKBP52 was phosphorylated by purified CK2. We expressed and purified deletion mutants of FKBP52 to determine the site(s) phosphorylated by CK2. Thr-143 in the hinge I region was identified as the major phosphorylation site for CK2. A synthetic peptide corresponding to this region was phosphorylated by CK2, and the peptide competitively inhibited the phosphorylation of other substrates by CK2. The 32Pphosphate labeling of FKBP52-expressing cells revealed that the same site is also phosphorylated in vivo. FK506 binding to FKBP52 did not affect the phosphorylation by CK2 and, conversely, the FK506-binding activity of FKBP52 was not affected by the phosphorylation. Most importantly, CK2-phosphorylated FKBP52 did not bind to HSP90. These results indicate that CK2 phosphorylates FKBP52 both in vitro and in vivo and thus may regulate the protein composition of chaperone-containing complexes such as those of steroid receptors and certain protein kinases.
The cdc25A protein phosphatase inhibitor dysidiolide (
1) has been synthesized via intermolecular Diels–Alder reaction of the triene
4 with crotonaldehyde and construction of a quaternary carbon ...center by methylation of the exocyclic enolate.
The catalyst composed of 0.25–0.025
mol
% of Pd(allyl)Cl
2 and 0.5–0.05
mol
% of the thioether-imidazolium chloride
3c was proven to be efficient in the Suzuki–Miyaura cross-coupling reactions of ...aryl bromides with arylboronic acids.
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