Rhodium carbenoid O-H insertion reactions with phenols; A facile method for the synthesis of trialkyl 2-aryloxyphosphonoacetates and their use in the preparation of 2-aryloxy-3-phenylpropanoates

(2aR*,5S*,6aS*,8aS*,E)-Ethyl 5-hydroxy-7,7,8a-trimethyl-8-oxo-2,2a,6,6a,7,8,8a,8b-octahydro-1H-pentaleno[1,6-bc]oxepine-4-carboxylate

The title compound, C₁₇H₂₄O₅, featuring a 2-carbeth­oxy-3-oxepanone unit in its intra­molecularly O—H⋯O hydrogen-bonded enol form, was obtained via [(CF₃CO₂)₂Rh]₂-catal­ysed intra­molecular O—H bond insertion in the α-diazo-ω-hy­droxy-β-ketoester, ethyl 4-[(1S,3aS,6R,6aS)-6-hy­droxy-2,2,3a-trimethyl-3-oxo-octa­hydro­penta­len-1-yl]-2-diazo-3-oxobutano­ate. The seven-membered oxacyclic ring, thus constructed on a cis-fused diquinane platform, was found to adopt a distorted boat–sofa conformation.

Design, synthesis, and biological evaluation of conformationally constrained cis-amide Hsp90 inhibitors

Conformationally constrained cis-amide chimeric inhibitors of Hsp90 have been synthesized and evaluated for their Hsp90 inhibitory activity. These new compounds exhibited Hsp90 ATPase inhibition and induced Hsp90-dependent client protein degradation in a dose-dependent manner. Biological data reported herein suggests that amide bond isomerization of geldanamycin derivatives plays an important role in affinity for the heteroprotein complex present in cancer cells.

Synthesis and evaluation of azaindole-α-alkyloxyphenylpropionic acid analogues as PPARα/γ agonists

A series of azaindole-alpha-alkyloxyphenylpropionic acid analogues was synthesized and evaluated for PPAR agonist activities. Structure-activity relationship was developed for PPARalpha/gamma dual agonism. One of the synthesized compound 7a was identified as a potent, selective PPARalpha/gamma dual agonist.

Two Complementary Approaches toward 2-Alkoxy Carboxylic Acid Synthesis from 1,3-Dioxolan-4-ones

Two complementary approaches to prepare 2-alkoxy carboxylic acids have been developed. Reductive ring opening of various 1,3-dioxolan-4-ones using TiCl(4)/Et(3)SiH or (t)BuMgCl affords the desired 2-alkoxy carboxylic acid in moderate to excellent chemical yield without loss of optical purity.

Linear free energy correlation analysis on the electronic effects of Rh(II) carbene O-H insertion

The relative rate constants for the Rh(II)-catalyzed insertion of diazoacetone into the O-H bond have been measured through intermolecular competitions. The kinetic data were subjected to Hammett correlation analysis, and mechanistic implication of the results with respect to a stepwise vs a concerted O-H insertion pathway is discussed.

Solid-phase synthesis of indolecarboxylates using palladium-catalyzed reactions

Polymer-supported, palladium-catalyzed cyclization reactions effectively synthesized indolecarboxylates. Palladium-catalyzed carbon-carbon bond-forming reactions of immobilized enaminoesters followed by transesterification yielded indole 2- or 3-carboxylates with various functional groups on the benzene ring. Indolecarboxylates were efficiently cyclized via an intramolecular palladium-catalyzed amination reaction of immobilized N-substituted dehydrohalophenylalanines, and immobilized N-acetyl-dehydroalanines were efficiently converted into indolecarboxylates via tandem Heck-amination reactions.

Alpha-phosphono lactone analogues of farnesyl pyrophosphate: an asymmetric synthesis via ring-closing metathesis

An alpha-phosphono lactone derivative of farnesol has been prepared, in both racemic and nonracemic forms, to provide a new type of farnesyl pyrophosphate analogue. Attempted preparation of the racemic alpha-phosphono lactone through rearrangement of a vinyl phosphate derived from the parent lactone resulted in both rearrangement and lactone ring opening, revealing that the farnesyl lactone was not stable to the excess of strong base required for the rearrangement. A procedure for C-P bond formation based on generation of the lactone enolate, reaction with a P(III) reagent, and oxidation was successful in providing the racemic alpha-phosphono lactone, in part, because only 1 equiv of strong base was required. The same strategy for phosphonate synthesis then was applied to the nonracemic farnesyl lactone, prepared through a sequence including allylation of farnesal with a nonracemic borane reagent, reaction of the product alcohol with acryloyl chloride, and formation of an unsaturated lactone through ring-closing metathesis. A similar strategy gave the corresponding racemic alpha-phosphono lactam through a six-step sequence from farnesal.

Construction of heterocyclic compounds by use of alpha-diazophosphonates: new one-pot syntheses of indoles and isocoumarins

[reaction: see text] alpha-Diazophosphonates, which have extremely useful properties from a synthetic point of view, are disclosed as 1,1-ambiphilic one-carbon building blocks for one-pot construction of various heterocyclic compounds. They are easily prepared and have higher stability by the effect of the phosphoryl group than corresponding alpha-diazocarbonyl compounds. Using this synthon, we have developed a novel, mild, and efficient synthetic method of 2,3-disubstituted indoles and 3,4-disubstituted isocoumarins.

Fluorine-substituted ligands for the peroxisome proliferator-activated receptor gamma (PPARgamma): potential imaging agents for metastatic tumors

The peroxisome proliferator-activated receptor gamma (PPARgamma), a primary regulator of lipid metabolism, is present in many tumor cell lines and animal tumor systems and, in some cases, can mediate effective antitumor therapy with potent synthetic ligands. In an approach to image tumors with positron-emission tomography (PET) based on their content of PPARgamma, we have synthesized two fluorine-substituted analogues of a high affinity ligand from the phenylpropanoic acid class. The analogue having the highest affinity for PPARgamma was labeled with the positron-emitting radionuclide fluorine-18. In tissue distribution studies in normal rats and in SCID mice bearing human breast tumor xenografts, this compound did not show evidence of receptor-mediated uptake. The prospects for using PPARgamma as a target for imaging tumors may be limited by the low receptor concentrations in tumors and by the pharmacokinetic behavior of this class of ligands, which appears to be more favorable for therapy than for imaging.

A new route to hindered tertiary amines

The Rh(2)(OAc)(4)-stabilized carbenoid derived from dimethyl diazomalonate has been found to insert into the N-H bond of sterically hindered secondary aliphatic amines to afford hindered tertiary aliphatic amines in quite satisfactory yields. For example dimethyl 2-(dicyclohexylamino)propanedioate was formed in 85% yield from dicyclohexylamine, and the severely hindered dimethyl 2-(2,2,6,6-tetramethyl-1-piperidinyl)propanedioate was formed in 38% yield from 2,2,6,6-tetramethylpiperidine. The Rh(2)(OAc)(4) - dimethyl diazomalonate reaction was found to work also for arylalkylamines and diarylamines. In these cases, small amounts of products resulting from formal insertion of the carbenoid into an aromatic C-H bond were detected. Substitution at ortho positions caused the yield of C-H insertion products to increase. Other diazo compounds, viz. ethyl diazoacetoacetate, 2-diazocyclohexane-1,3-dione, and 2-diazo-5,5-dimethylcyclohexane-1,3-dione, performed satisfactorily in Rh(2)(OAc)(4)-catalyzed reactions with arylalkylamines and diarylamines, but led to complicated reaction mixtures with dialkylamines.