Synthesis of the core structure of acutumine

[reaction: see text] The tricyclic core of the bioactive natural product acutumine has been synthesized. Key steps include an oxidative phenolic coupling to form a masked o-benzoquinone, an anionic oxy-Cope rearrangement to construct an all-carbon quaternary center, and a Michael-type cyclization to form an amine-bearing quaternary carbon. The target compound exists in solution as an enol, in contrast to related compounds that are ketones. A model explaining these observations is presented.     

Synthesis of an isomer of the germacranolide isoaristolactone

Photocycloadditlon of (+)-isoplperltenone and cyclobutene-1-carboxylic acid gives an adduct which upon reduction with NaCNBH₃ followed by thermolysis yields an isomer of isoaristolactone in an overall yield of 26%.     

Investigation of the one-pot synthesis of quinolin-2-(1H)-ones and the discovery of a variation of the three-component Ugi reaction

Rapid access to the quinolin-2-(1H)-one scaffold is afforded by a sequential 4 component Ugi–Knoevenagel condensation of an aminophenylketone, an aromatic aldehyde possessing electron donating moieties, cyanoacetic acid and an aliphatic isocyanide, in moderate to good yields (49–71%). Interestingly, when the reaction is performed using aromatic aldehydes bearing electron withdrawing moieties or isocyanides containing aromatic or ester units, a mixture of a quinolin-2-(1H)-one and an α-amino amide (Ugi three-component adduct) is afforded in varying ratios. Further when the reaction is performed utilizing a combination of an isocyanide-containing aromatic or carbonyl unit, and an aldehyde possessing an electron withdrawing functionality, the Ugi three-component adduct is exclusively afforded. In our hands this new variation of the Ugi 3CR proved to be efficient and robust affording analogues in good yields (51–70%).     

Exploring the chemistry of epoxy amides for the synthesis of the 2'-epi-diazepanone core of liposidomycins and caprazamycins

New synthetic strategies have been explored for the synthesis of the structural core of liposidomycins and caprazamycins, an intriguing class of complex nucleoside-type antibiotics. This structural core is comprised of a cyclic diazepanone system linked to an uridyl fragment. The various synthetic approaches have in common that they originate from an epoxy amide derived from uridine, obtained via reaction of uridyl aldehyde 19 with an amide-stabilized sulfur ylide. Two different strategies were shown to be efficient in constructing the diazepanone ring system: (a) a reductive amination of an epoxy aldehyde with N-methylamine with subsequent intramolecular oxirane ring opening and (b) a carbene insertion reaction of an acyclic diazoamine precursor.     

Synthesis of phosphorus analogs of TSAO-T

Phosphorus Analogs of TSAO bearing an oxaphospholene ring instead of an oxathiole dioxide ring at C-3′ position were prepared. Strategy developed previously on saccharidic moiety was used with introduction of an electron withdrawing α group neighboring the phosphorus atom. Biological evaluation on both HIV-1 and HCV showed that these compounds have no activity.     

Synthesis of new arylidene derivatives of 3-aminorhodanine

The synthesis of new arylidene derivatives of 3 -aminorhodanine has been effected. It has been established that the condensation of 3-aminorhodanine with aldehydes in an alcoholic medium gives 3′-arylidene derivatives. Similar reactions in an ammoniacal medium lead to 5-derivatives of 3-aminorhodanine. 3′, 5-Diarylidene derivatives can be obtained by condensing 3′-aminorhodanine with an excess of an aldehyde in glacial acetic acid, except for the salicylidene and 9-anthrylidene derivatives, the synthesis of which can be carried out only in two stages.     

Asymmetric synthesis of the core of AMPTD, the key amino acid of microsclerodermins F-I

We report a stereoselective synthesis of the five consecutive stereocenters of AMPTD in seven steps. Highlights include an Evans glycolate aldol reaction, the use of a Weinreb amide as an aldehyde masking group, and a Mannich reaction with an Ellman-type chiral sulfimine.     

西安市某辖区2～6岁儿童全血样品微量元素含量状况调查

摘要对西安市某辖区妇幼保健站及多家幼儿园920名2～6岁身体健康儿童的全血样品进行微量元素检测,统计得到该区域正常儿童微量元素的含量范围,为准确了解西安地区某区域2-6岁正常儿童体内微量元素正常含量提供了参考数据。     

Extraction of water miscible organic dyes by reverse micelles of alkyl glucosides

The extraction of methyl orange or methylene blue from an aqueous phase to an organic phase of reverse micelles of alkyl glucosides was investigated. Dodecyl glucoside, a biodegradable and biocompatible surfactant, was employed as a kind of alkyl glucosides, since a stable Winsor II system consisting of the water-in-oil type microemulsion and aqueous phases was formed when an organic solution containing dodecyl glucoside was contacted with an aqueous solution. The water content in the reverse micellar organic phase increased with an increase in the concentration of dodecyl glucoside. The extraction ratio of dyes also increased with increasing the concentration of dodecyl glucoside. Furthermore, the extraction ratio of dyes was dramatically dependent upon the pH of an aqueous phase and temperature.     

Application of palladium-catalyzed allylic arylation to the synthesis of a (+/-)-7-deoxypancratistatin analogue

Palladium-catalyzed coupling of an aryl siloxane and an allylic carbonate proceeded in good yield to give an adduct that was converted to an analogue of (+/-)-7-deoxypancratistatin.     

An approach to the synthesis of gelsemine: the intramolecular reaction of an allylsilane with an acyliminium ion for the synthesis of one of the quaternary centres

We describe an efficient synthesis (summarised in Schemes 8 and 10) of an advanced intermediate (34) suitable for the synthesis of gelsemine. The key steps in the synthesis are (i) the Diels-Alder reaction between 1-tetrahydropyranyloxycyclohexa-1,3-diene (10) and methyl β-nitroacrylate (11) giving an adduct (12), in which the chiral centre in the tetrahydropyranyl ring is produced substantially in only one sense, (ii) the rearrangement of a bicyclo [2.2.2] octane (23) into a bicyclo[ 3.2.1] octane (24), where control of which bridge migrates is achieved by a choice of the counterion in the Lewis acid, and (iii) the efficient formation of the quaternary centre by an intramolecular reaction between an allylsilane group and an acyliminium ion (33 → 34).     

Regioselective allylzincation of alkenylboronate

[reaction: see text] Boryl substitution on an olefin activates the olefinic double bond toward addition of an organozinc reagent. Addition of an allylic zinc reagent to an alkenylboronate thus takes place smoothly to afford a variety of gem-zincio/boryl species. Theoretical studies with density functional calculations on the reaction pathway revealed that the reaction proceeds via a zincio-ene reaction rather than a bora-Claisen rearrangement.     

A facile synthesis of phytosphingosine from diisopropylidene-D-mannofuranose

In the present study, an efficient method with a high overall yield for preparing phytosphingosine and an analogue was developed. Starting with commercially available 2,3;5,6-di-O-isopropylidene-d-mannofuranose, a variety of lipid moieties were incorporated to obtain phytosphingosine and an analogue. Through an eight-step manipulation, phytosphingosine was obtained with an overall yield of 57%.     

Vapor pressure and sublimation rate of molecular crystals: role of internal degrees of freedom

It is a common practice to approximate the desorption rate of atoms from crystal surfaces with an expression of the form nueff exp(-DeltaE/kBT), where DeltaE is an activation barrier to desorb and nueff is an effective vibrational frequency approximately 10(12) s(-1). For molecular solids, however, such an approximation can lead to a many orders of magnitude underestimation of vapor pressure and sublimation rates due to neglected contributions from molecular internal degrees of freedom. Here, we develop a simple working formula that yields good estimates for a general molecular (or atomic) solid and illustrate the approach by computing equilibrium vapor pressure of three different molecular solids and an atomic solid, as well as the desorption rate of a foreign (inhibitor) molecule from the surface of a molecular solid.     

Stereoselective Synthesis of Morpholines via Copper-Promoted Oxyamination of Alkenes

A new copper(II) 2-ethylhexanoate-promoted addition of an alcohol and an amine across an alkene (oxyamination) is reported. The alcohol addition is intramolecular, while coupling with the amine occurs intermolecularly. Several 2-aminomethyl morpholines were synthesized in good to excellent yields and diastereoselectivities.     

Low-temperature synthesis of titanium disulfide nanotubes

A low-temperature gas reaction was used to successfully synthesize TiS2 nanotubes with an outer diameter of approximately 20 nm, an inner diameter of approximately 10 nm, an interlayer spacing of approximately 0.57 nm, and an average length of 2-5 microm.     

pH-controlled switching of photocurrent direction by self-assembled monolayer of helical peptides

A novel molecular system, where the photocurrent direction can be reversibly switched by changing the pH of the solution, was prepared on gold from helical peptides carrying a photosensitizer and a carboxyl group at the terminal. Upon photoexcitation of the photosensitizer in an aqueous solution containing an electron donor and acceptor at pH 10, the monolayer generated an anodic photocurrent due to enhancement of the dipole moment by a carboxylate anion, while it generated an opposite cathodic photocurrent at pH 3.4     

Theoretical investigation of changes in the thermodynamic properties of water in the region near an electrode upon the discharge of an hydroxonium ion

A method for investigating solutions in the region near an electrode has been developed in the framework of the Monte Carlo method. The energies of the reorganization of water upon the transfer of an electron to a hydroxonium ion from the unpolarized surface of an absolutely solid charged electrode in the range of surface charge densities from +0.056 to –0.640 C/m² and upon the reverse process have been calculated. The hydration energies of an H₃O⁺ cation and an H₃O^– radical in the region near an electrode have been calculated. The effective interactions of an ion and a nonpolar molecule with an electrode in a solution have been analyzed.Translated from Teoreticheskaya i Éksperimental/naya Khimiya, Vol. 26, No. 5, pp. 596–600, September–October, 1990.     

Electrochemical partial fluorination of organic compounds. 80. Synthesis of cyclic alpha-arylthio-alpha-monofluorophosphonate esters

[Reaction: see text]. Seven-membered cyclic alpha-monofluorophosphonate esters such as 2-allyloxy-3-fluoro-3-phenylthio-4,7-dihydro-[1, 2]-oxaphosphinine-2-oxide were successfully synthesized in moderate total yield as 41% from open-chain allyl phosphonates having an alpha-arylthio group as an electroauxiliary using an alternative sequence of anodic fluorination and ring-closing olefin metathesis (RCM). On the other hand, in an attempt to synthesize an eight-membered analogue, a different type of seven-membered fluorinated cyclic product was formed predominantly by the RCM reaction between the allyloxy groups.     

Electrocatalytic Multicomponent Reaction for Synthesis of Nanoparticles of Spirooxindole Derivatives from Isatins,Malononitrile, and Dimedone

An electrocatalytic multicomponent synthesis of nanoparticles of spirooxindole is described, using an electrogenerated base of the anion of propanol in a one‐pot, three component condensations of an isatins, dimedone, and malononitrile in an undivided cell in the presence of sodium bromide as an electrolyte at 50°C.