Search

PBr3-mediated reductive deoxygenation of α-aryl-pyridinemethanols to provide arylmethylpyridines is described, the alcohol substrate scope is explored, free radical trap TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) is introduced, and the hydrogen source of the methylene product is defined. The unexpected reaction enabled us to prepare previously inaccessible, novel EP1 antagonists.

The title pyridines are obtained by convenient reaction of pyridine triflates with various aryl boronic acids.

A cobalt–N-heterocyclic carbene catalytic system promotes pyridine-directed olefinic C–H alkylation reactions using a variety of primary and secondary alkyl chlorides under mild conditions. Radical clock experiments suggest that the reaction involves single-electron transfer from the cobalt intermediate to the alkyl chloride.

The two-step one-pot procedure delivers substituted 2-aminopyrazolo[1,5-a]pyridines as scaffolds in medicinal chemistry.

We have successfully synthesized 3,4,5-substituted 1,4-dihydropyridines (1,4-DHPs) from amine hydrochloride salts, aldehydes, and acetals in good yields without the addition of a catalyst. The synthesized 1,4-DHPs exhibit various wavelengths of fluorescence, which could be tuned by changing the substituents at the 3- and 5-positions of the 1,4-DHPs.

A Co/TiO2 catalyst shows high activity in the dehydrogenation of various secondary alcohols (I) and (III) to afford the corresponding ketones.

Treatment of 2-alken-4-ynoates with methyl- or aryl-Grignard reagents and iron(II) chloride (10 mol%) afforded 5-methyl- or 5-aryl-3,4-alkadienoates in good yields as a single isomer after aqueous work-up. Likewise, (2-alken-4-ynoyl)oxazolidinones afforded (5-methyl-3,4-alkadienoyl)oxazolidinones. The aldol-type reaction with acetone was also possible in place of the hydrolytic work-up.

The reaction affords siladioxocine derivatives with (Z)- or (E)-geometry at the endocyclic double bond, strongly depending on the sterical and configurational vicinity.

Quinoline N-oxides (IV) are synthesized starting from nitrophenyl derivatives (III) or from nitrochalcones (V).

Tumescenamide A (Ia) induces gene expression under the control of the insulin-degrading enzyme promoter.

The target compounds are prepared from the aryl zinc reagents, generated from pinacol boronic esters or boroxines with comparable yields and enantioselectivities.

Labeling experiments confirm that the MEP (2-C-methyl-D-erythritol-4-phosphate) pathway is used for the biosynthesis of gifhornenolone A (I) and B (II) in the title microorganism.

Feeding experiments with [1,2-13C2]acetate and [2-13C,2H3]acetate in suspension cultures of A. elliptica demonstrate that campesterol has C-26 (the pro-R methyl group at C-25) and C-27 (the pro-S methyl group at C-25) arising from C-6 and C-2 of mevalonate (MVA), respectively. In contrast, dihydrobrassicasterol has C-26 and C-27 derived from C-2 and C-6 of MVA, respectively. In both 24-methylcholesterols, the methyl group derived fron C-2 and C-6 of MVA retained two and three deuterium atoms, respectively. Furthermore, no signal due to a deuterium atom at C-24 or C-25 originating from [2-13C,2H3]acetate was found for campesterol and dihydrobrassicasterol. These data suggest that both campesterol and dihydrobrassicasterol are biosynthesized by regio-facial specific reduction of the 24(25)-double bond of the 24-methyl-24(25)-ene side-chain which is formed by double-bond isomerization of Δ24(28)-sterol.

Anhydrous tetrabutylphosphonium hydrogen bifluoride (2), dihydrogen trifluoride prepared from aq. tetrabutylphosphonium hydroxide and aq. HF, and tetrabutylphosphonium fluoride prepared from 2 and BunLi were shown to be useful fluoride sources for selective nucleophilic fluorination of oxiranes, alkyl halides, alcohols and sulfonates of aliphatic and steroidal species.

The magnitude of spontaneous polarization of liquid crystals forming chiral smectic C phases is discussed in terms of a dipole moment and rotational barrier neighbouring the chiral centre of the liquid-crystalline molecules. Using quantitative relations obtained from a molecular-orbital calculation for some compounds having polar groups such as –CO2–, –O– and –CO–, the molecular structure of a chiral dioxaborinane derivative with a large spontaneous polarization was designed; this was then synthesized and confirmed to form an Sc* phase exhibiting a large spontaneous polarization of 200 nC cm –2 as predicted.

The p-quinol acetate (1a) reacted with allyltrimethylsilane in dichloromethane in the presence of acid (BF 3 .Et 2 O or CF 3 COOH) to give 8-allylcorypalline (3), while in acetonitrile to give 4-allylcorypalline (7), regioselectively. Plausible pathway on formation of 3 and 7 is described

Upon irradiation 2-acyloxy-1-methoxycarbonylcyclohexenes readily undergo photo-Fries rearrangement to give 2-acyl-2-methoxycarbonylcyclohexanones in good yields and among them 2-aroyloxy-1-methoxycarbonylcyclohexenes also undergo a novel 1,5-aroyl migration according to irradiation conditions to give 4-aroyl-2-methoxycarbonylcyclohexanones, which result from 1,3-aroyl migration following photo-Fries rearrangement.

Two and three dimensional assemblies self-assembled monolayers (SAMs) and hydrogen-bonded co-crystals, respectively show substantial changes in their supramolecular structures with seemingly minor changes in the structure of their molecular atomic constituents. The structure of SAMs obtained by adsorption of alkanethiols onto silver and copper are indistinguishable, although the atomic radii of silver and copper are different. The structure of the SAM on silver is different from that on gold, although the atomic radii of these metals are essentially the same. A macroscopic property of the SAMs, wetting, is not affected by these structural differences. Co-crystals formed from derivatives of barbiturates and melamines form hydrogen bonded tapes in the solid state. These tapes provide a template for studying the packing forces within crystals.

Two types of surface hydroxyl groups on maghemite have been identified and their acidities evaluated. One of these surface groups bonds to the surface iron ions of the octahedral sites and shows a stretching vibration mode of infrared absorption at 3690 cm−1. The other bonds to the tetrahedral sites and vibrates at 3630 cm−1. The acidity of the groups positioned at the octahedral sites was evaluated as 12.5 in the pKa value while that of those on the tetrahedral sites was found to be 7.9. A charge transfer mechanism between these neighboring two types of hydroxyl groups is proposed as an explanation for these acidities.

Polyacrylates and polymethacrylates having various 1,3,2-dioxaborinane derivatives as pendants have been synthesized and demonstrated to form chiral smectic C and/or smectic A phases which are more stable than those formed by the corresponding monomes. They provide a new family of chiral liquid crystalline side-chain polymers containing boron atoms in the pendant group.

α-Acetylstyrylphosphonates were conveniently synthesized from 2-oxopropylphosphonates and substituted (dimorpholinomethyl)benzenes (aminals). 4-Benzylidenemorpholinium carboxylates, generated from aminals by the action of α-halo acids, reacted with the phosphonates to give the products by elimination of the amine. The yields were influenced by the nature of substituents and their position in the phenyl ring and could be improved by adjustment of the acidities of the reacted acids. α-Acetylstyrylphosphonates containing various substituents on every position (at the 2-. 3-, or 4-position) in the phenyl ring were obtained generally in excellent yields using monochloroacetic acid

Alkenes and their functionalized derivatives were readily converted to the corresponding halofluorides with tetrabutylphosphonium dihydrogentrifluoride as combined with N-halosuccinimides or 1,3-dibromo-5,5-dimethylhydantoin in highly regio-, stereo-, and chemoselective manners. In particular, alkenes having a oxirane or primary hydroxyl group also underwent halofluorination selectively in good yields.

Copper catalyzed conjugate addition of Grignard reagents to enones was effected with high 1,4-diastereoinduction and was used for the preparation of taxane precursors.

The absolute stereochemistry of the Ophiorrhiza alkaloid ophiorrhizine has been defined as shown in formula [(-)−1] by a chemical correlation with the Cinchona alkaloid cinchonine through cincholoipon ethyl ester [(+)−3] and the lactim ether [(+)−2]. The correlation was achieved by the chiral synthesis of ophiorrhizine [(-)−1] from (+)−2 via the inter- mediates [(+)−5], [(+)−7], [(+)−6], (8), [(-)−9], [(-)−10], (11), [(-)−12], and [(-)−13]

Optically active 3,7-dibenzyloxy-4,8-di-t-butyldimethylsiloxy-5,5-dimethyl-6-p-methoxybenzyloxy-2-octanone (2) has been synthesized by way of diastereoselective aldol reaction between 4-benzyloxy-5-t-butyldimethylsiloxy-2,2-dimethyl-3-p-methoxy-benzyloxypentanal (3) and ketene silyl acetal 4 using MgBr2·OEt2 as a catalyst. The chiral pentanal 3 was synthesized either by asymmetric aldol reaction of both prochiral aldehyde 5 and ketene silyl acetal 4 using a chiral Lewis acid or by diastereoselective aldol reaction between the chiral aldehyde 6 derived from L-serine and the lithium enolate derived from methyl isobutyrate.

Trachyspic acid, a new metabolite that inhibited heparanase, was isolated from the culture broth of Talaromyces trachyspermus SANK 12191. Its structure was deduced from NMR spectral analyses and chemical reactions as a tricarboxylic acid derivative containing a spiroketal. The IC50 value of trachyspic acid against heparanase was 36 microM.

2-Alkynylnitrobenzenes (I) are used as starting materials for the synthesis of arylketones of type (II), quinolines of type (IV) or acridine derivatives, e.g. (VI).

A facile method for the synthesis of 2-arylquinolines via Yb(O-Tf)3-catalyzed reaction of anilines, arylaldehydes and 1,1-diethoxyethane is developed.