An efficient total synthesis of the anticancer agent (+)-spisulosine (ES-285) from Garner’s aldehyde

An efficient total synthesis of (+)-spisulosine (ES-285) was completed in nine steps from (S)-Garner’s aldehyde. The vicinal amino alcohol moiety with anti-configuration was achieved by a highly diastereoselective addition of vinyl magnesium bromide to Garner’s aldehyde. The long hydrocarbon chain of the antitumor natural product was installed via olefin cross metathesis of the benzyl-protected allylic alcohol with an appropriate olefin counterpart followed by hydrogenation.     

Syntheses,characterization, X-ray crystal structures and emission properties of copper(II), zinc(II) and cadmium(II) complexes of pyridyl–pyrazole derived Schiff base ligand – Metal selective ligand binding modes

The varying coordination modes of the title ligand, L [5-methyl-1-(pyridin-2-yl)-N′-[pyridin-2-ylmethylidene]pyrazole-3-carbohydrazide] towards the different metal centers is reported by preparation and characterization of Cu(II), Zn(II) and Cd(II) complexes, [Cu(L)NO₃.H₂O](NO₃) (1) [Zn(L)₂](ClO₄)₂·2DMF (2) and [Cd(L)(I)₂] (3) respectively. In 1, the neutral ligand serves as tetradentate 4 N donor where both pyridine and pyrazole nitrogen atoms of pyridyl–pyrazole part are coordinatively active, leaving the carbonyl oxygen of the carbohydrazide part inactive. The same pyridine and pyrazole N atoms remain abstained from the coordination process towards the Zn(II) and Cd(II) metal centers. For 2 and 3 the ligand behaves as a tridentate NNO donor where the two nitrogen atoms come from azomethine, pyridine of pyridine-2-carbaldehyde parts and O from carbonyl oxygen atoms (carbohydrazide part). The complex 1 and 2 are distorted octahedral while complex 3 adopts distorted square pyramidal geometry. All the complexes are X-ray crystallographically characterized.     

Estimation of capsaicin through scanning densitometry and evaluation of different varieties of capsicum in India

Capsicum annuum L. (family: Solanaceae) possesses therapeutic benefits for the treatment of rheumatism, neuropathy, psoriasis, flatulence and so on. In this study fruits of four different varieties of C. annuum from four different geographical regions in India were evaluated based on their total content of capsaicin. Ethanol extracts of the fruits were used. HPTLC plates were developed in a mobile phase containing benzene, ethyl acetate and methanol (75:20:5). Densitometric scanning was performed at a wavelength of 283 nm in the absorbance mode. The calibration curve was described by the equation Y=393.587+3.836*X with a correlation coefficient (r) of 0.99890. The content of capsaicin in Nagaland, Manipur, West Bengal and Shimla varieties was found to be 3.71%, 1.78%, 0.54% and 0.06%, respectively. The developed densitometric method was found to be specific, accurate and precise. A recovery study and precision showed low levels of %RSD values. The linearity range of the curve for capsaicin was found to be 300-900 ng per spot. The limit of detection and the limit of quantification values were determined to be 31 and 94 ng, respectively, proving the sensitivity of the method. Thus the method can be used to control the total content of capsaicin on an industrial scale.     

Three‐Component Self‐Assembly of a Series of Triply Interlocked Pd12 Coordination Prisms and Their Non‐Interlocked Pd6 Analogues

Template‐assisted formation of multicomponent Pd₆ coordination prisms and formation of their self‐templated triply interlocked Pd₁₂ analogues in the absence of an external template have been established in a single step through Pd? N/Pd? O coordination. Treatment of cis‐[Pd(en)(NO₃)₂] with K₃tma and linear pillar 4,4′‐bpy (en=ethylenediamine, H₃tma=benzene‐1,3,5‐tricarboxylic acid, 4,4′‐bpy=4,4′‐bipyridine) gave intercalated coordination cage [{Pd(en)}₆(bpy)₃(tma)₂]₂[NO₃]₁₂ ( 1 ) exclusively, whereas the same reaction in the presence of H₃tma as an aromatic guest gave a H₃tma‐encapsulating non‐interlocked discrete Pd₆ molecular prism [{Pd(en)}₆(bpy)₃(tma)₂(H₃tma)₂][NO₃]₆ ( 2 ). Though the same reaction using cis‐[Pd(NO₃)₂(pn)] (pn=propane‐1,2‐diamine) instead of cis‐[Pd(en)(NO₃)₂] gave triply interlocked coordination cage [{Pd(pn)}₆(bpy)₃(tma)₂]₂[NO₃]₁₂ ( 3 ) along with non‐interlocked Pd₆ analogue [{Pd(pn)}₆(bpy)₃(tma)₂](NO₃)₆ ( 3′ ), and the presence of H₃tma as a guest gave H₃tma‐encapsulating molecular prism [{Pd(pn)}₆(bpy)₃(tma)₂(H₃tma)₂][NO₃]₆ ( 4 ) exclusively. In solution, the amount of 3′ decreases as the temperature is decreased, and in the solid state 3 is the sole product. Notably, an analogous reaction using the relatively short pillar pz (pz=pyrazine) instead of 4,4′‐bpy gave triply interlocked coordination cage [{Pd(pn)}₆(pz)₃(tma)₂]₂[NO₃]₁₂ ( 5 ) as the single product. Interestingly, the same reaction using slightly more bulky cis‐[Pd(NO₃)₂(tmen)] (tmen=N,N,N′,N′‐tetramethylethylene diamine) instead of cis‐[Pd(NO₃)₂(pn)] gave non‐interlocked [{Pd(tmen)}₆(pz)₃(tma)₂][NO₃]₆ ( 6 ) exclusively. Complexes 1 , 3 , and 5 represent the first examples of template‐free triply interlocked molecular prisms obtained through multicomponent self‐assembly. Formation of the complexes was supported by IR and multinuclear NMR (¹H and ¹³C) spectroscopy. Formation of guest‐encapsulating complexes ( 2 and 4 ) was confirmed by 2D DOSY and ROESY NMR spectroscopic analyses, whereas for complexes 1 , 3 , 5 , and 6 single‐crystal X‐ray diffraction techniques unambiguously confirmed their formation. The gross geometries of H₃tma‐encapsulating complexes 2 and 4 were obtained by universal force field (UFF) simulations.     

Synthesis and Structural Characterization of New Divanada‐ and Diniobaboranes Containing Chalcogen Atoms

The reaction of [Cp_nMCl_4?x] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η⁵‐C₅H₅) with LiBH₄ ? THF followed by thermolysis in the presence of dichalcogenide ligands E₂R₂ (E=S, Te; R=2,6‐(tBu)₂‐C₆H₂OH, Ph) and 2‐mercaptobenzothiazole (C₇H₅NS₂) yielded dimetallaheteroboranes [{CpV(μ‐TePh)}₂(μ₃‐Te)BH ? thf] ( 1 ), [(CpV)₂(BH₃S)₂] ( 2 ), [(CpNb)₂B₄H₁₀S] ( 3 ), [(CpNb)₂B₄H₁₁S(tBu)₂C₆H₂OH] ( 4 ), and [(CpNb)₂B₄H₁₁TePh] ( 5 ). In cluster 1 , the V₂BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge‐fused V₂BS tetrahedron clusters. Cluster 3 can be considered as an edge‐fused cluster in which a trigonal‐bipyramidal unit (Nb₂B₂S) has been fused with a tetrahedral core (Nb₂B₂) by means of a common Nb₂ edge. In addition, thermolysis of an in‐situ‐generated intermediate that was produced from the reaction of [Cp₂VCl₂] and LiBH₄ ? THF with excess BH₃ ? THF yielded oxavanadaborane [(CpV)₂B₃H₈(μ₃‐OEt)] ( 6 ) and divanadaborane cluster [(CpV)₂B₅H₁₁] ( 7 ). Cluster 7 exhibits a nido geometry with C_2v symmetry and it is isostructural with [(Cp*M)₂B₅H_9+n] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η⁵‐C₅Me₅). All of these new compounds have been characterized by ¹H NMR, ¹¹B NMR, and ¹³C NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds  1 – 4 , 6 , and 7 .     

Effect of dispersion on the diffusion zone in two-phase laminar flows in microchannels

Aim of the present work is to investigate the reaction–diffusion process of a two species system under laminar flow in a T-shaped microchannel. A zone formed at the interface between the aqueous solutions of these two species is affected by advection and diffusion. Through theoretical analyses and experimental results, the effect of dispersion has been shown to influence this diffusion zone. We have defined a parameter called effective diffusivity, to account for the dispersion effects and observed it to be a function of the channel Peclet number. In the limiting case of low Peclet number, this parameter is constant and turns out to be equal to the molecular diffusivity. We have also related effective diffusivity and the dispersion coefficient through scaling estimates.     

Electrochemistry and photoelectron spectroscopy of oxomolybdenum(V) complexes with phenoxide ligands: effect of para substituents on redox potentials,heterogeneous electron transfer rates,and ionization energies

Complexes of the form (Tp*)MoOCl(p-OC(6)H(4)X) and (Tp*)MoO(p-OC(6)H(4)X)(2) (Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate and X = OEt, OMe, Et, Me, H, F, Cl, Br, I, and CN) were examined by electrochemical techniques and gas-phase photoelectron spectroscopy to probe the effect of the remote substituent (X) on electron-transfer reactions at the oxomolybdenum core. Cyclic voltammetry revealed that all of these neutral Mo(V) compounds undergo a quasireversible one-electron oxidation (Mo(VI)/Mo(V)) and a quasireversible one-electron reduction (Mo(V)/Mo(IV)) at potentials that linearly depend on the electronic influence (Hammett sigma(p) parameter) of X. The first ionization energies for (Tp*)MoO(p-OC(6)H(4)X)(2) (X = OEt, OMe, H, F, and CN) were determined by photoelectron spectroscopy. A nearly linear correlation was found for the Mo(VI)/Mo(V) oxidation potentials in solution and the gas-phase ionization energies. Calculated heterogeneous electron-transfer rate constants show a slight systematic dependence on the substituent.     

Domino "[3+3]-cyclization-homo-Michael" reactions of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes

The Lewis acid mediated domino "[3+3]-cyclization-homo-Michael" reaction of 1,3-bissilyl enol ethers with 1,1-diacylcyclopropanes allows an efficient one-pot synthesis of functionalized salicylates containing a halogenated side chain. A great variety of substitution patterns could be realized by variation of the starting materials and of the Lewis acid. The mechanism of the domino process was studied.     

A simplified green chemistry approach to the Biginelli reaction using ‘Grindstone Chemistry’

Grindstone Chemistry--a greatly evolved version of Toda’s method of grinding solids together for solvent-free chemical reactions--has been described and its usefulness illustrated by the successful application of this technique to a simplified process for conducting the multi-component Biginelli reaction for the synthesis of physiologically active tetrahydropyrimidinones.     

Densitometric HPTLC Analysis of Juglone,Quercetin, Myricetin,Rutin, Caffeic Acid,and Gallic Acid in Juglans regia L.

JPC – Journal of Planar Chromatography – Modern TLC - Asensitive, selective, and precise high-performance thin-layer chromatography (HPTLC) method was developed for simultaneous...