Gold-Catalyzed Heteroannulation of Anthranilic Acids with Alkynes: Synthesis of 3,1-Benzoxazin-4-ones.

We demonstrated a rapid and facile approach for the synthesis of various 3,1-benzoxazin-4-ones via a gold-catalyzed heteroannulation of readily available nonprotected anthranilic acids and simple aryl alkynes. Our preliminary mechanistic investigation indicated that the double incorporation of alkynes into anthranilic acids occurs through the formation of bisenamine intermediates.

Palladium-Catalyzed Heteroannulation of Salicylamides with Propargyl Carbonates: Synthesis of 1,4-Benzoxazepin-5-ones.

Herein, we report a palladium-catalyzed method to synthesize 1,4-benzoxazepin-5-ones using salicylamides and propargyl carbonates. The heteroannulation provides a wide range of products in good to excellent yields with broad functional group tolerance. In addition, H2O is used as a low-cost, abundant, and safe solvent, which is important in terms of sustainability.

Chlorobenzene-driven palladium-catalysed lactonisation of benzoic acids.

Herein, we developed a palladium-catalysed C-H cyclisation of benzoic acids in chlorobenzene without additional oxidants. The key to the success of these reactions is the use of chlorobenzene, which serves a dual role as a solvent and an oxidant, thus providing a simple and efficient method for synthesising phthalides.

Gold(I)-Catalyzed Heteroannulation of Salicylic Amides with Alkynes: Synthesis of 1,3-Benzoxazin-4-one Derivatives.

Gold(I)-catalyzed heteroannulation affords the efficient and straightforward construction of heterocyclic compounds. Herein, we developed a gold(I)-catalyzed heteroannulation of salicylic amides with alkynes producing a broad range of 1,3-benzoxazin-4-ones. The utility of this protocol was highlighted by synthesizing variously substituted benzoxazinones containing quaternary carbon centers, showing a high functional group tolerance and excellent atom economy of the thus introduced reaction course.

Site-selective iodine atom transfer in fluorinated alkyl iodides via 1,5-hydrogen atom transfer.

The direct and selective functionalization of inert C-H bonds via intramolecular hydrogen atom transfer (HAT) is an increasingly powerful tool in organic synthesis. Herein, we designed an efficient and facile iodine atom transfer in fluorinated alkyl iodides via 1,5-HAT. Our process enables site-selective iodination of unreactive C(sp3)-H bonds to afford di- and tri-fluorinated alkyl iodides in good yields. Furthermore, our process shows excellent atom economy and high functional group tolerance, including methyl, methoxy, chloro, cyano, and silyl moieties.

Nitrile Synthesis via Desulfonylative-Smiles Rearrangement.

Herein, we designed a simple nitrile synthesis from N-[(2-nitrophenyl)sulfonyl]benzamides via base-promoted intramolecular nucleophilic aromatic substitution. The process features redox-neutral conditions as well as no requirement of toxic cyanide species and transition metals. Our process shows broad scope and various functional group compatibility, affording a variety of (hetero)aromatic nitriles in good to excellent yields.

Retention and molecular-recognition mechanisms of molecularly imprinted polymers for warfarin derivatives and their application for the determination of warfarin in human serum.

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF), 4'-chlorowarfarin (CWF), 4'-bromowarfarin (BWF), 4'-nitrowarfarin (NWF) and 4'-methylwarfarin (MWF) (MIPWF, MIPCWF, MIPBWF, MIPNWF and MIPMWF, respectively) were prepared using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate as a functional monomer and crosslinker, respectively, by multi-step swelling and polymerization. The retention and molecular-recognition properties of those MIPs were evaluated in HILIC, and reversed- and normal-phase modes. According to 1H NMR studies, one-to-three complex formation of one WF or CWF molecule with three 4-VPY molecules occurred. Via computational approaches, the intermolecular interaction modes and energies between WF derivatives and 4-VPYs were evaluated by semi-empirical quantum chemistry methods and density functional theory calculations. Three major possible hydrogen bonding interaction modes were identified: the interactions between the 4-hydroxy group, α-proton (methylene C-H) and α-proton (methyl C-H) of the WF derivative and the nitrogen atoms of 4-VPYs. In HILIC and normal-phase modes, the interaction energies showed satisfactory correlations with the retention factors of the WF derivatives. In reversed-phase mode, the retention factors of the WF derivatives were described by the hydrophobicity and the acidity of the 4-hydroxy groups of the WF derivatives. These results demonstrate that three hydrogen bonding interactions in HILIC and normal-phase modes, and hydrogen bonding or ionic interactions and hydrophobic interactions in reversed-phase mode play important roles in the retention and molecular-recognition of the WF derivatives on MIPs. Furthermore, MIPBWF was successfully applied to the determination of WF in human serum by column-switching LC with high accuracy, precision and selectivity and without template-leakage problems.

Determination of Abiraterone and Its Metabolites in Human Serum by LC-ESI-TOF/MS Using Solid-phase Extraction.

We developed and validated a liquid chromatography-electrospray ionization-time of flight/mass spectrometry method for the determination of abiraterone (Abi) and its metabolites (Δ4-Abi, 3-keto-5α-Abi, 3α-OH-5α-Abi and 3ß-OH-5α-Abi) in human serum using Abi-d4 as the internal standard. As a pretreatment procedure of serum samples, solid-phase extraction based on a silica-gel cartridge was used. The relative recovery of Abi and its metabolites was over the ranges of 84.5 - 109.2% at a concentration of 6.0 ng mL-1 for Abi and 0.6 ng mL-1 for its metabolites. The method was free from matrix effects. The calibration curve of Abi was linear over the range of 2.0 - 400 ng mL-1 and those of its metabolites over the ranges 0.2 - 40 ng mL-1. The results of the intra- and inter-day accuracy and precision data were within the FDA acceptance criteria. The optimized method was applied for the determination of Abi and its metabolites in human serum after oral administration of Abi acetate.

Enantioseparation of warfarin derivatives on molecularly imprinted polymers for (S)- and (R)-chlorowarfarin.

Monodisperse molecularly imprinted polymers (MIPs) for warfarin (WF), 4'-chlorowarfarin (CWF), (S)-CWF and (R)-CWF (MIPWF, MIPCWF, MIP(S)-CWF and MIP(R)-CWF, respectively) were prepared using 4-vinylpyridine (4-VPY) and ethylene glycol dimethacrylate (EDMA) as a functional monomer and a crosslinker, respectively, by multi-step swelling and polymerization. The molar ratio of a template molecule, 4-VPY to EDMA was 6:18:25 or 4:18:25. The retention and molecular recognition properties of MIPWF and MIPCWF were evaluated using a mixture of sodium phosphate buffer or ammonium formate and acetonitrile in reversed-phase LC. WF and CWF on these MIPs gave the maximal retentions at mobile phase pH 7, and those retentions were decreased with an increase of acetonitrile content. The retention and imprinting factors were in the order of WF < CWF < 4'-bromowarfarin (BWF) on MIPWF and MIPCWF in neutral mobile phases. On the other hands, in acidic mobile phases the retention factors were in the same order with those in neutral mobile phases, while the imprinting factors of WF and CWF were higher on the respective MIPs. These results suggest that ionic or hydrogen bonding interactions, hydrophobic interactions and π-π interactions could work for the retention and molecular recognition of WF, CWF and BWF on these MIPs in a reversed-phase mode. Furthermore, MIP(S)-CWF and MIP(R)-CWF could separate WF, CWF and BWF enantiomers in acidic mobile phases.

Palladium-catalyzed dehydrogenative C-H cyclization for isoindolinone synthesis.

In this paper Pd-catalyzed intramolecular dehydrogenative C(sp3)-H amidation for the synthesis of isoindolinones is described. This method features the use of a Pd/C catalyst and the addition of a stoichiometric amount of oxidant is not necessary. A mechanistic study suggested the possible formation of H2 gas during the reaction.

A solvent-dependent chirality-switchable thia-Michael addition to α,ß-unsaturated carboxylic acids using a chiral multifunctional thiourea catalyst.

An asymmetric thia-Michael addition of arylthiols to α,ß-unsaturated carboxylic acids using a thiourea catalyst that bears arylboronic acid and tertiary amine moieties is reported. Both enantiomers of the Michael adducts can be obtained in high enantioselectivity and good yield merely by changing the solvent. The origin of the chirality switch in the products was examined in each solvent via spectroscopic analyses.

Retention and molecular-recognition mechanisms of molecularly imprinted polymers for promazine derivatives.

Monodisperse molecularly imprinted polymers (MIPs) for promazine derivatives [promazine (PZ), methylpromazine (MPZ), chlorpromazine (CPZ) and bromopromazine (BPZ)], MIPPZ, MIPMPZ, MIPCPZ and MIPBPZ, were prepared using methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylate as a crosslinker by multi-step swelling and polymerization. The retention and molecular-recognition properties of the obtained MIPs were evaluated using LC in hydrophilic interaction chromatography (HILIC) and reversed-phase modes. In computational approaches, intermolecular interaction modes and energies between PZ derivatives and MAAs were evaluated at the HF/6-311G(d,p) level. The interaction energies of PZ, MPZ, CPZ and BPZ with 4 equivalents of MAAs were calculated. The results indicated that the interaction of the aliphatic amine moiety of a PZ derivative with MAA gave almost similar interaction energies at the HF/6-311G(d,p) level, and that the interaction of the sulfur atom of a phenothiazine scaffold with MAA was also the case. The third interaction of the aromatic amine of a PZ derivative with MAA was in the order of MPZ > PZ > CPZ > BPZ presumably due to the change of basicity by the electron-donating or electron-withdrawing effect of a subsituent. Furthermore, the fourth attractive modes of CPZ and BPZ were suggested to be the interaction of their halogen atoms with MAA through both halogen bonding and hydrogen bonding, while PZ and MPZ were suggested to have the weak C-H ⋅⋅⋅ π interaction with MAA. In HILIC mode, the interaction energies at the HF method had good correlation with the retention factor of a PZ derivative on each MIP, indicating that in addition to the shape recognition, the attractive electrostatic interactions would be more responsible for its retention rather than the dispersion energies. Furthermore, in addition to the shape recognition, ionic and hydrophobic interactions, and halogen bonding and hydrogen bonding (the last interaction seems to be weak) seem to work for the retention and molecular-recognition of PZ derivatives on the MIPs in reversed-phase mode.

Evaluation of molecularly imprinted polymers for chlorpromazine and bromopromazine prepared by multi-step swelling and polymerization method-The application for the determination of chlorpromazine and its metabolites in rat plasma by column-switching LC.

Monodisperse molecularly imprinted polymers (MIPs) for chlorpromazine (CPZ) and bromopromazine (BPZ), MIPCPZ and MIPBPZ, were prepared using methacrylic acid as a functional monomer and ethylene glycol dimethacrylate as a crosslinker by multi-step swelling and polymerization. The retention and molecular-recognition properties of MIPCPZ and MIPBPZ were evaluated using a mixture of potassium phosphate buffer and acetonitrile or a mixture of water and acetonitrile including ammonium formate as a mobile phase in reversed-phase LC. On MIPBPZ, CPZ, BPZ and imipramine (IMP) gave the maximal retention factors at a mobile-phase pH 8, while the maximal imprinting factors were obtained at a mobile-phase pH 7. Each MIP recognized a template molecule the most, while CPZ metabolites, desmethyl CPZ (DM-CPZ), CPZ sulfoxide (CPZ-SO) and 7-hydroxy CPZ (7-OH-CPZ), were moderately recognized on MIPCPZ and MIPBPZ. Furthermore, both MIPs gave the similar retention and molecular-recognition for CPZ and its metabolites. For avoiding the template-leakage problems, MIPBPZ was used as the pretreatment column for the determination of CPZ and its metabolites in rat plasma in column-switching LC with UV detection. In addition to DM-CPZ and CPZ-SO, didesmethyl CPZ (DDM-CPZ) and CPZ N-oxide (CPZ-NO) were speculated as the metabolite in rat plasma after administration of CPZ using LC-ESI-TOF-MS, while 7-OH-CPZ was not detected. The column-switching LC method was validated and applied for the determination of CPZ and its metabolites, DM-CPZ, DDM-CPZ, CPZ-SO and CPZ-NO, in rat plasma after intravenous and oral administration of CPZ using IMP as an internal standard.

Inhibition of angiogenesis and tumor growth by a novel 1,4-naphthoquinone derivative.

Hit, Lead & Candidate Discovery Antiangiogenesis therapy is a promising way for treatment of solid cancers, and many angiogenesis inhibitors that target vascular endothelial growth factor (VEGF) or its receptors have been developed. We explored novel antiangiogenic compounds other than anti-VEGF drugs by screening our synthetic compound library and found that 6-thiophen-3-yl-2-methoxy-1,4-naphthoquinone (6-TMNQ) had potential as a novel angiogenesis inhibitor. This paper describes the effects of 6-TMNQ on angiogenesis and tumor growth in vitro and in vivo. 6-TMNQ inhibited serum-, VEGF-, and basic fibroblast growth factor (bFGF)-stimulated proliferation of endothelial cells in a concentration-dependent manner, but had no effect on the proliferation of fibroblasts. VEGF-induced activation of VEGF receptor-2 in endothelial cells was not affected by the compound. 6-TMNQ markedly abrogated both migration and tube formation of endothelial cells. Orally administered 6-TMNQ inhibited angiogenesis in response to VEGF or bFGF in mice in a dose-dependent manner. Furthermore, when tumor-bearing mice were treated with 6-TMNQ, increase in tumor size was significantly prevented due to inhibition of angiogenesis in the tumor tissues. These results demonstrate that 6-TMNQ is an orally available compound that selectively inhibits endothelial cell proliferation and migration, and abrogates angiogenesis, resulting in the prevention of tumor growth. The mechanism of 6-TMNQ action is different from that of conventional anti-VEGF drugs.

Development of hemiacetal esterified levofloxacin to prevent chelation with metal-containing drugs.

OBJECTIVES: To avoid the chelate formation between levofloxacin (LVFX) and aluminium hydroxide in gastrointestinal tract, an ethoxycarbonyl 1-ethyl hemiacetal ester of levofloxacin (LVFX-EHE) was synthesised as a prodrug. METHODS: The effects of aluminium hydroxide on the bioavailability of LVFX following oral administration of LVFX-EHE were investigated in rats. Furthermore, the effects of aluminium hydroxide on small intestinal absorption of LVFX and LVFX-EHE when subjected to a hydrolysis experiment using in situ everted gut sac were investigated, and the minimal inhibitory concentrations (MICs) of LVFX and LVFX-EHE for various intestinal bacteria were measured. KEY FINDINGS: When LVFX-EHE was co-administered with and without aluminium hydroxide, the AUC0-4 h values of LVFX hydrolysed from LVFX-EHE were similar to that of LVFX alone. In everted gut sac experiments, LVFX-EHE was efficiently absorbed even in the presence of aluminium ions after 1 h of incubation, whereas the absorption of LVFX decreased significantly in the presence of aluminium ions. MIC values of LVFX-EHE were far higher than LVFX. CONCLUSIONS: This study suggests the benefit of ethoxycarbonyl 1-ethyl hemiacetal esterification of the carboxyl group of new quinolone as a prodrug which is able to avoid chelate formation.

Rhodium-Catalyzed Cyclization of 2-Ethynylanilines in the Presence of Isocyanates: Approach toward Indole-3-carboxamides.

Catalytic synthesis of indole-3-carboxamides from 2-ethynylanilines and isocyanates was achieved in the presence of a rhodium catalyst through a tandem-type, cyclization-addition sequence. This tandem-type process can be performed under mild reaction conditions, affording 2,3-disubstituted indoles in a one-pot manner generally in good to excellent yields. The broad substrate scope and good functional group compatibility make the method highly efficient and widely applicable, providing a facile and entirely novel route toward variously substituted indole-3-carboxamides.

Unusual O-alkylation of 2-hydroxy-1,4-naphthoquinone utilizing alkoxymethyl chlorides.

A new type of O-alkylation of 2-hydroxy-1,4-naphthoquinone with alkoxymethyl chlorides is described. The reaction course can be controlled by the choice of base and yields O-alkylated or O-alkoxymethylated products in high yield with high selectivity.

Highly enantioselective (-)-sparteine-mediated lateral metalation-functionalization of remote silyl protected ortho-ethyl N,N-dialkyl aryl O-carbamates.

We report the enantioselective, lateral deprotonation of ortho-protected or functionalized tertiary N,N-dialkyl aryl O-carbamates 5-7 (Scheme 2 ) and meta-protected carbamates 14, 15, and 20 (Schemes 5 and 7 ) by s-BuLi/(-)-sparteine and subsequent quench with a variety of electrophiles to give products 11-13 and 16, 17, and 21 in yields up to 96% and enantiomeric ratios up to 99:1. The influence of organolithium reagents, ratio of organolithium/(-)-sparteine pair versus N,N-dialkyl aryl O-carbamate starting materials, temperature, solvents, electrophiles, substituents located ortho or meta to the O-carbamate moiety, and O-carbamate N-substituents was investigated. The identical absolute configuration of the stereogenic center of the major enantiomers of the products, as established by single-crystal X-ray analysis for substrates (S)-11c, (S)-19, and (S)-21a, provides evidence for a consistent stereochemical course in the enantioselective deprotonation. Mechanistic investigations, including an estimate of the configurational stability of the benzyllithium species 9 (starting from 12e; Scheme 8 ) and 23 (starting from 17e; Scheme 9 ), both derived by tin-lithium exchange, and 24 (starting from 20; Scheme 9 ) are reported. The experimental results, together with semiempirical molecular orbital calculations (PM3/SMD), are consistent with a process in which enantioinduction occurs in the deprotonation step (Scheme 11 ).

Highly efficient synthesis of quinoxalinone-N-oxide via tandem nitrosation/aerobic oxidative C-N bond formation.

An efficient method for constructing quinoxalinone-N-oxides from cyanoacetanilides has been developed. This transformation can be achieved using inexpensive reagents and molecular oxygen under mild conditions, thus offering a practical pathway to quinoxalinone-containing pharmaceuticals such as ataquimast and opaviraline.

Synthesis of biologically active (-)-dehydroiso-ß-lapachone and the determination of its absolute configuration.

Synthesis of dehydoriso-ß-lapachone (1) in both racemic and enantioenriched forms is achieved starting from reduced naphthoquinone equivalents. As for the synthesis of enantioenriched dehydroiso-ß-lapachone, introduction of the asymmetric center was carried out by catalytic asymmetric epoxidation of the unfunctionalized trisubstituted olefin using Shi epoxidation diketal catalyst. The construction of isopropenylfurano-1,2-(ß)-naphthoquinone was carried out by acidic ring-opening reaction of the epoxynaphthalene and the following diammonium cerium(IV) nitrate (CAN) oxidation. The absolute configuration of naturally occurring (-)-dehydroiso-ß-lapachone was finally determined as (R) by comparing the measured optical rotation value of the synthetic (R)-dehydroiso-ß-lapachone.