Biotransformation of (+)-(1R,2S)-fenchol by the larvae of common cutworm (Spodoptera litura)

Biotransformation of (+)-(1R,2S)-fenchol by the larvae of Spodoptera litura was carried out. Substrate was converted to three new terpenoids, (+)-(1R,2S)-10-hydroxyfenchol, (+)-(1R,2R,3S)-8-hydroxyfenchol and (−)-(1S,2S,6S)-6-exo-hydroxyfenchol, and one known terpenoid, (−)-(1R,2R,3R)-9-hydroxyfenchol. These structures were established by NMR, IR, specific rotation and mass spectral studies.     

Synthesis of (+)-anatoxin-a using enyne metathesis

Synthesis of N-tosylanatoxin-a was achieved by metathesis of enyne in cis-substituents on a pyrrolidine derivative. Metathesis reactions of enyne having terminal alkyne using various ruthenium-carbene complexes did not give a good results. However, when the terminal alkyne was protected with a TMS group, the reaction proceeded smoothly using a second-generation ruthenium-carbene complex to give the desired cyclized compound in high yield. Oxymercuration followed by Dess-Martin oxidation afforded N-tosylanatoxin-a.     

Polyfluorinated arylnitrosamines

N-Methyl-, N-n-butyl-, N-t-butylperfluoroarylamines undergo nitrosation with nitrous acid to give the corresponding N-nitroso derivatives. Perfluoroaryl groups were selected from the benzene, indane, biphenyl, naphthalene and pyridine series. According to ¹H and ¹⁹F NMR spectra, N-nitroso-N-methyl derivatives of polyfluoroarenes consist of E and Z isomers with the former prevailing. The more bulky n-butyl group promotes an increase in the formation of Z isomers. Only Z isomers have been obtained from N-t-butyl derivatives of perfluorinated 4-toluidine and 4-aminopyridine. The structure of the Z isomer of N-nitroso-N-methylperfluoro-4-toluidine is confirmed by X-ray data.     

N-(Diethoxyphosphoryl)-O-benzylhydroxylamine—a convenient substrate for the synthesis of N-substituted O-benzylhydroxylamines

Easily available N-(diethoxyphosphoryl)-O-benzylhydroxylamine was shown to be convenient, orthogonally protected substrate for regioselective N-alkylation by means of diverse halides under basic conditions (sodium hydride/tetrabutylammonium bromide). An efficient procedure for dephosphorylation of N-substituted N-(diethoxyphosphoryl)-O-benzylhydroxylamine to provide N-substituted O-benzylhydroxylamines was also established.     

Engineering of pha operon on Cupriavidus necator chromosome for efficient biosynthesis of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) from vegetable oil

Cupriavidus necator H16C_Ac, previously constructed for production of poly((R)-3-hydroxybutyrate-co-(R)-3-hydroxyhexanoate) [P(3HB-co-3HHx)] from soybean oil, was further engineered aiming to increase 3HHx composition in the copolyester. PHA synthase gene derived from Aeromonas caviae on the H16C_Ac chromosome was replaced by a gene encoding the N149S/D171G mutant and this recombination enhanced PHA productivity as well as slightly increased 3HHx composition. Manipulation of phaA_Cn locus partially reduced the amount of 3HB unit concomitantly with relative increase of 3HHx composition, whereas deletion of phaB1_Cn resulted in drastic decline of 3HB unit in P(3HB-co-3HHx). Insertion of phaJ_Ac encoding (R)-specific enoyl-CoA hydratase from A. caviae into pha operon significantly enlarged 3HHx fraction without negative effects on the cell growth and polyester accumulation. Consequently, efficient production of P(3HB-co-3HHx) with 3HHx composition of 5.7-9.9 mol% was successfully achieved from soybean oil by the engineered strains.     

A new, one-pot, three-component synthesis of 4H-pyrido[1,2-a]pyrimidines, 4H-pyrimido[1,2-a]pyrimidines, and 4H-pyrazino[1,2-a]pyrimidines

A new, one-pot and three-component synthesis of 4H-pyrido[1,2-a]pyrimidines, 4H-pyrimido[1,2-a]pyrimidines, and 4H-pyrazino[1,2-a]pyrimidines is described. The reactive 1:1 zwitterionic intermediate, formed by the addition of isocyanides to dialkyl acetylenedicarboxylates, was trapped by N-(2-heteroaryl)amides to yield a ketenimine intermediate, which was cyclized and then rearranged under the reaction conditions to afford the title compounds under mild reaction conditions in good yields. Single-crystal X-ray analysis conclusively confirms the structure of the obtained bridgehead bicyclic 6-6 heterocyclic compounds.     

New stereoselective synthesis of thiamphenicol and florfenicol from enantiomerically pure cyanohydrin: a chemo-enzymatic approach

Thiamphenicol and florfenicol have been synthesized stereoselectively from enantiomerically pure 4-methylsulfanyl-mandelonitrile, which was obtained by hydrocyanation reaction of 4-methylsulfanyl-benzaldehyde catalyzed by (R)-hydroxynitrile lyase of Badamu (Prunus communis L. var. dulcis Borkh, almond from Xinjiang, China). It was found to be a highly effective bio-catalyst for this reaction after an extensive screening.     

Selective O-acylation of unprotected N-benzylserine methyl ester and O,N-acyl transfer in the formation of cyclo[Asp-Ser] diketopiperazines

The synthesis of two diastereomeric cyclo[Asp-N-Bn-Ser] diketopiperazines (2a and 2b) was investigated. Initial formation of the Boc-aspartyl-N-benzyl serine isopeptide methyl esters (4a and 4b) was observed, which derive from the selective O-acylation of unprotected (S)- or (R)-N-benzylserine. This unexpected O-acylation is preferred over the formation of the tertiary amide and the resulting ester bond is stable in solution to O,N-acyl transfer. The O,N-acyl migration is then triggered by cleavage of the Boc protecting group and treatment with base, which also promotes immediate cyclization to the diketopiperazines.     

Comparative study of biosurfactant produced by microorganisms isolated from formation water of petroleum reservoir

Biosurfactant produced by Pseudomonas aeruginosa, Bacillus subtilis and Rhodococcus erythropolis that isolated from the formation water of Chinese petroleum reservoir has been compared in surface abilities and oil recovery. Maximum biosurfactant production reached to about 2.66 g/l and the surface tension of liquid decreased from 71.2 to 22.56 mN/m using P. aeruginosa. Three strains exhibited a good ability to emulsify the crude oil, and biosurfactant of P. aeruginosa attained an emulsion index of 80% for crude oil which was greater than other strains. Stability studies were carried out under the extreme environmental conditions, such as high temperature, pH, salinity and metal ions. Results showed an excellent resistance of all biosurfactants to retain their surface-active properties at extreme conditions. It was found that the biosurfactants from three isolated bacteria showed a good stability above pH of 5, but at lower pH (from 1 to 5) they will harmfully be affected. They were able to support the condition up to 20 g/l salinity. P. aeruginosa biosurfactant was even stable at the higher salinity. Regarding temperature, all produced biosurfactants demonstrated a good stability in the temperature up to 120 °C. But stability of three biosurfactants was affected by monovalent and trivalent ions. Oil recovery experiments in physical simulation showed 7.2-14.3% recovery of residual oil after water flooding when the biosurfactant of three strains was added. These results suggest that biosurfactants of these indigenous isolated strains are appropriate candidates for enhanced oil recovery with a preference to biosurfactant of P. aeruginosa.     

Facile synthesis of C-phosphanylformamidines via a carbene pathway

A direct synthetic approach to C-phosphanyl-N,N-dialkyl-N′-aryl(alkyl)-formamidines was developed. It was shown that phosphorylation of the formamidines proceeds at the nitrogen atom affording N-phosphanylformamidinium salts. Upon deprotonation, these salts gave C-phosphanylformamidines via formation of carbenes followed by a 1,2-phosphorus shift.     

Three practical approaches for the synthesis of novel 4,7-dihetarylpyrazolo[1,5-a][1,3,5]triazines

Novel 4,7-dihetarylpyrazolo[1,5-a][1,3,5]triazines were synthesized from three different approaches. The first one, involved a one-step reaction between 5-amino-3-hetaryl-1H-pyrazoles and O,S-diethyl hetaroylimidothiocarbonates or S,S-diethyl hetaroylimidodithiocarbonates under solvent-free conditions employing microwave irradiation as the energy source. In the second approach, conventional heating under reflux in DMF as solvent was used instead of the microwave irradiation; and the third one was achieved from a two-step sequence through the treatment of 5-amino-3-hetaryl-1H-pyrazoles with hetaroyl isothiocyanates and the subsequent S-alkylation and cyclization process in DMF as solvent. Some intermediates were isolated and characterized to support the regiochemistry of the studied reactions. The structures of the new compounds were unambiguously established by spectroscopic and analytical techniques.     

Interaction of 3,5-di-tert-butyl-o-benzoquinone with secondary amines—a pathway to new sterically hindered N,N-disubstituted o-aminophenols

The interaction of 3,5-di-tert-butyl-o-benzoquinone with secondary amines has been studied. The synthetic procedure was developed in order to synthesize a series of new N,N-disubstituted o-aminophenols. The interaction of 3,5-di-tert-butyl-o-benzoquinone with dimethylamine leads to 2-(N,N-dimethylamino)-4,6-di-tert-butyl-phenol, which is oxidized in the reaction medium by the parent 3,5-di-tert-butyl-o-benzoquinone forming spirocompound 4,5′,6,7′-tetra-tert-butyl-3′-methyl-3′H-spiro[1,3-benzodioxol-2,2′-[1,3]benzoxazole].     

Comb copolymers of polystyrene-poly(tert-butyl (meth)acrylate) prepared by combination of nitroxide mediated polymerization and photoinduced iniferter technique

Comb copolymers consisting of polystyrene backbone and poly(tert-butyl (meth)acrylate) side chains were synthesized by combination of nitroxide (TEMPO)-mediated polymerization (NMP) and photoinduced grafting from macro-iniferters. First, poly(chloromethylstyrene), PCMS, with the degree of polymerization and two random poly(styrene-co-chloromethylstyrene) copolymers, P(S-co-CMS), with similar but different content (8 and 14 mol%) of CMS units, were synthesized by NMP. In the second step the CMS units both in the homopolymer and the copolymers were converted to N,N-diethyldithiocarbamyl groups (DC) yielding photosensitive multifunctional macro-iniferters. Finally, tert-butyl methacrylate tBuMA was grafted from the synthesized polymer backbones by iniferter technique under UV-irradiation yielding copolymers polystyrene-graft-poly(tert-butyl methacrylate) PS-g-P(tBuMA). Grafting initiated by the macro-iniferters containing ∼6-11 DC initiating sites per macromolecule proceeded by pseudo-living polymerization mechanism, i.e., the number-average molecular weight increased with conversion and the SEC traces were unimodal. In contrast, photo-polymerization initiated by highly functionalized polystyrene backbone was poorly controlled. Hydrolysis of loosely grafted copolymers PS-g-P(tBuMA) afforded amphiphilic copolymers polystyrene-graft-poly(methacrylic acid). Molecular parameters of the synthesized graft copolymers in dilute THF solutions were determined by scattering (DLS, SLS, SAXS) and viscometric measurements.     

The fragmentation reaction of 16R-bromopregnane-3S,20S-diol

16R-Bromopregnane-3S,20S-diol reacted with potassium t-butoxide to afford androst-16-en-3S-ol in a moderate yield via fragmentation reaction. The latter is a key intermediate for the synthesis of 5α-androst-16-en-3-one, as boar sex pheromone, and other steroidal drugs. In addition, 16R,20S-epoxypregnane-3S-ol was also obtained as a major product by changing the reaction solvent.     

Syntheses and structures of zinc and tin(II) compounds with hemilabile N-silyl-tert-butylamido and N-silyl-p-tolylamido ligands that contain pendent tert-butoxy groups

Syntheses and solid-state structures of zinc and tin(II) compounds, containing the N-silyl-amide ligands (O^tBu)(NR)SiMe₂, R = ^tBu (L^tBu), or R = p-tolyl (L^pTol), are reported. The N-silyl amines were synthesized by modified published procedures from commercially available Me₂SiCl₂, ^tBuOH, and ^tBuNH₂, or p-Me-C₆H₄NH₂, respectively. Treatment of SnCl₂ with LiL^pTol furnished Sn(L^pTol)₂, which was X-ray structurally characterized and shown to contain two covalent Sn-N bonds and two asymmetrical O → Sn donor bonds. The single-crystal X-ray structure of Sn(L^tBu)₂ revealed a much more symmetrically-coordinated, pseudo-trigonal-bipyramidal tin atom. Aminolysis of diethylzinc with HL^pTol produced [EtZn(L^pTol)]₂, which crystallized as a centrosymmetric dimer, containing four-coordinate zinc atoms connected by bridging amides. Zinc dichloride, by contrast, reacted with two equivalents of LiL^tBu to produce the homoleptic, pseudo-spirocyclic Zn(L^tBu)₂.     

Efficient one-pot trans-dihydroxylation of 2H-pyrans using dimethyldioxirane (DMD): synthesis of trans-3,4-dihydroxy-3,4-dihydro-O-methyloctandreolones, orixalone D, and trans-3,4-dihydroxy-3,4-dihydromollugin natural products

An efficient one-pot formation of trans-diols on 2H-pyranyl rings was achieved by dimethyldioxirane in wet acetone. This new methodology was applied to the synthesis of natural products containing trans-diol on the pyranyl rings such as trans-3,4-dihydroxy-3,4-dihydro-O-methyloctandreolones, orixalone D, and trans-3,4-dihydroxy-3,4-dihydromollugin.     

The first isolation of C-glycosylanthocyanin from the flowers of Tricyrtis formosana

A novel C-glycosylanthocyanin was isolated from the flowers of Tricyrtis formosana cultivar Fujimusume, and its structure was elucidated to be 8-C-β-d-glucopyranosylcyanidin 3-O-(6-O-malonyl)-β-d-glucopyranoside by chemical and spectroscopic methods.     

Synthesis of Closo-1,7-Carboranyl Alkyl Amines

Of the three closo-carborane isomers (C₂B₁₀H₁₂), closo-1,2-carborane has been used most widely in the synthesis of carboranyl amines. However, closo-1,2-carboranes are prone to deboronation to nido-7,8-carborane under various conditions including attack by basic amino groups. In order to overcome this problem, closo-1,7-carboranyl ethyl-, propyl-, and butylamine were synthesized, which should be more stable towards basic deboronation than their closo-1,2-carboranyl counterparts. These closo-1,7-carboranyl amines (5, 18 and 19) were synthesized using two different methods, both starting from the corresponding closo-1,7-carboranyl alkyl iodides (3, 14 and 15). One of the carboranyl alkyl amine (5) was conjugated with folic acid to form a closo-1,7-carborane-folic acid bioconjugate (20).     

Phytoremediation of lead with green onions (Allium fistulosum) and uptake of arsenic compounds by moonlight ferns (Pteris cretica cv Mayii)

Phytoremediation has been investigated as an alternative to excavation to remediate contamination in soil. In this work, Allium fistulosum (green onions) and Pteris cretica cv Mayii (moonlight ferns) were investigated for phytoremediation. Green onions were planted in lead-spiked soil, and chelating agents were introduced to enhance the uptake of lead by the plants. Lead uptake was low in the absence of chelating reagents. Ethylenediaminetetraacetic acid (EDTA) significantly enhanced the concentration of lead in the stems of green onions, while propylenediaminetetraacetic acid (PDTA) did not induce lead absorption.Moonlight ferns (P. cretica cv Mayii) were planted in a hydroponic system to which arsenic (III), arsenic (V), and monomethylarsenate (MMA) were added with hydroponic solution. Ferns exposed to arsenic (III) showed the highest extraction of arsenic followed by ferns exposed to arsenic (V). The extraction of arsenic by the ferns was higher when arsenic (III) was mixed with arsenic (V) than the combination of arsenic (III) and MMA. These results suggest that inorganic arsenic is phytoextracted preferentially to MMA.     

An efficient synthesis of highly substituted pyrroles from β-oxodithiocarboxylates

α-Oxoketene-N,S-acetals, prepared by the reaction of alkyl glycinate hydrochlorides with β-oxodithiocarboxylates followed by alkylation, underwent cyclization in presence of chloromethyleneiminium salt derived from POCl₃/DMF to afford alkyl-3-aryl-4-formyl-5-(alkylsulfanyl)-1H-pyrrole-2-carboxylates in excellent yields. Alkyl-3-aryl-5-(alkylsulfanyl)-1H-pyrrole-2-carboxylates were formed in moderate yields when the same N,S-acetals were treated with DBU.