The biosynthesis of the alkaloids of croton sparsiflorus morong

Incorporation of tyrosine, dopa, dopamine, 4-hydroxyphenylpyruvic acid, (±)-, norcoclaurine-1-carboxylic acid, -norcoclaurine, -coclaurine, and -N-methylcoclaurine into N-methylcrotsparine, N-methylcrotsparinine and N-methylsparsiflorine in Croton sparsiflorus Morong has been studied. The evidence supports the direct oxidative coupling of (+)-, and (-)-N-methylcoclaurines to give N-methylcrotsparine and N-methylcrotsparinine respectively. Tracer experiment show that N-methylcrotsparine undergoes dienone-phenol rearrangement to give N-methylsparsiflorine. A double labelling experiment with (±)-N[¹⁴C]methyl[1-³H]coclaurine demonstrated that the H atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion. The intermediacy of norcoclaurine-1-carboxylic acid and specific incorporation of dehydro-N-methylcoclaurinium salt into the bases have been demonstrated.     

Electrophilic fluorinating reagent mediated synthesis of fluorinated alpha-keto Ethers,benzil, and 6,6'-dialkoxy-2,2'-bipyridines

Interactions of various fluorinated and nonfluorinated alcohols with trans-stilbene in the presence of electrophilic reagents were studied. Under neat conditions, reactions of trans-stilbene (1) with fluorinated alcohols, R(f)OH (R(f) = CF3CH2-, CFH2CH2-, CF3CF2CH2-, CF2H(CF2)3CH2-, (CF3)2CH-, (CF3)3C- (2a-f) in the presence of an electrophilic reagent, 1-(chloromethyl)-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (Selectfluor) or N,N-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) (MEC-31), gave alpha-keto ethers (3a-f) and benzil (4) in good to moderate yields. alpha-Keto ether and benzil formation was very much dependent on the reaction time, the degree of fluorination of the alcohols, and whether a solvent such as CH3CN, DMF or DMA was utilized. In solution, alpha-keto ethers and benzil did not form. Interestingly, under neat conditions, nonfluorinated alcohols, ROH (R = CH3-, CH3CH2-, CH3CH2CH2-, CH3CH2CH2CH2-, CH3CH2CH2CH2CH2CH2-) (5g-k) did not react with trans-stilbene in the presence of MEC-31 but gave 6,6'-dialkoxy-2,2'-bipyridines (6g-k), regioselectively, in excellent isolated yields. On the other hand, fluorinated alcohols did not react with MEC-31. Reaction of MEC-31 with an excess of diethylene glycol (7) gave the bipyridine derivative (8) in 88% isolated yield. Reaction of 8 either with diethylaminosulfur trifluoride (DAST) or bis(2-methoxyethyl)aminosulfur trifluoride (Deoxofluor) readily produced the corresponding difluoro derivative (9) in 85% isolated yield. All new compounds have been characterized by spectroscopic and elemental analysis.     

Pyrene-Hydrazone-π···Hole Coupled Turn-on Fluorescent and Naked- Eye Colorimetric Sensor for Cyanide: Role of Homogeneous π-Hole Dispersion in Anion Selectivity

A pyrene based probe associated with π···hole – hydrazone as one of the recognizing elements is synthesized and its turn in to a selective colorimetric and turn-on fluorescent sensor, (L³) for cyanide anion. This chemo sensor show high selectivity towards cyanide anion through photo electron transfer (PET) mechanism. The binding strength and sensitivity of the chemo sensor L³ towards cyanide are found to be 2.0 X 10⁴, and 4.44 x 10^-4 respectively. We have compared this high selectivity of the receptor towards cyanide, with our previously reported receptors L¹ and L². The detailed UV-Vis, Emission, ¹H-NMR, IR spectroscopic and Molecular Electrostatic Potential (MEP) studies reveals that the homogeneous π···hole dispersion in the aromatic ring governing the selectivity of the receptor towards cyanide anion. Such a positive π···hole homogeneous dispersion is missing in the case of sensor L², instead we have polarized π···hole dispersion towards 2^nd and 4^th position of di-nitrophenyl chromophoric unit in L².

Graphical Abstract

     

Synthesis and Bioassay of Ethyl-2- (2-((Diethoxyphosphoryl) (Aryl) Methylamino)Thiazol-4-Yl)-2-(Methoxyimino)Acetates

Abstract

A simple, efficient, and environmentally benign methodology has been accomplished for the synthesis of α-aminophosphonates by one-pot three-component reaction of ethyl-2-amino-α-(methoxy-imino)-4-thiazoleacetate, aldehydes, and diethylphosphite by using Amberlyst-15 as catalyst at room temperature under solvent-free conditions. Their chemical structures were characterized by infrared (IR), NMR (¹H, ¹³C & ³¹P), mass spectral, and elemental analysis. All the title compounds were screened for radical-scavenging activity by 1,1-diphenyl-2-picrylhydrazyl (DPPH), nitic oxide (NO), and hydrogen peroxide (H₂O₂) methods.

Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional text and figures.     

Micron Particles of AlN/Al: Efficient,Novel, and Reusable Heterogeneous Catalyst for the Synthesis of Bis(indolyl)methanes

The present work introduces for the first time the catalytic utility of micron particulate aluminium nitride (AlN/Al) as a novel and reusable heterogeneous catalyst for the synthesis of bis(indolyl)methanes involving the electrophilic substitution of indoles on aldehydes. The catalyst is recyclable and works without any significant change in its catalytic activity.     

Simultaneous high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS-MS) analysis of cyanide and thiocyanate from swine plasma

An analytical procedure for the simultaneous determination of cyanide and thiocyanate in swine plasma was developed and validated. Cyanide and thiocyanate were simultaneously analyzed by high-performance liquid chromatography tandem mass spectrometry in negative ionization mode after rapid and simple sample preparation. Isotopically labeled internal standards, Na¹³C¹⁵N and NaS¹³C¹⁵N, were mixed with swine plasma (spiked and nonspiked), proteins were precipitated with acetone, the samples were centrifuged, and the supernatant was removed and dried. The dried samples were reconstituted in 10 mM ammonium formate. Cyanide was reacted with naphthalene-2,3-dicarboxaldehyde and taurine to form N-substituted 1-cyano[f]benzoisoindole, while thiocyanate was chemically modified with monobromobimane to form an SCN-bimane product. The method produced dynamic ranges of 0.1–50 and 0.2–50 μM for cyanide and thiocyanate, respectively, with limits of detection of 10 nM for cyanide and 50 nM for thiocyanate. For quality control standards, the precision, as measured by percent relative standard deviation, was below 8 %, and the accuracy was within ±10 % of the nominal concentration. Following validation, the analytical procedure successfully detected cyanide and thiocyanate simultaneously from the plasma of cyanide-exposed swine.     

Global Behaviour of Solutions of Nonlinear Delay Difference Equations*

In this paper global asymptotic stability and asymptotic behaviour of solutions of nonlinear delay difference equations has been studied and a few sets of sufficient conditions for global asymptotic stability are derived.     

Electron-impact-induced 3,3-sigmatropic rearrangement and cyclization in phenyl allenylmethyl ethers

A 3,3-sigmatropic rearrangement in the M^+· of phenyl allenylmethyl ether is proposed for the observed losses of CO, C₂H₄, and CH₃. Direct cyclization in the M^+· also leads to the [M?CH₃] ion. The presence of sulfur as the heteroatom in phenyl allenylmethyl sulfide does not significantly influence the occurrence of Claisen rearrangement. Ortho interaction of the nitro group with the allenyl double bond in the side chain leads to characteristic fragment ions in 2-nitrophenyl allenylmethyl ether. Linked scans, high-resolution mass spectrometry, collision-activated dissociation-B/E linked-scan spectra, and D-labeling have been employed to support the proposed mechanisms and ion structures.