First Stereoselective Synthesis of the Cytotoxic Polyketide (4R)‐1‐(3,5‐Dihydroxyphenyl)‐4‐hydroxypentan‐2‐one

The first stereoselective synthesis of the cytotoxic polyketide (4R)‐1‐(3,5‐dihydroxyphenyl)‐4‐hydroxypentan‐2‐one ( 1 ) was achieved from readily available propylene oxide and 3,5‐dimethoxybenzyl alcohol. The synthesis involves Jacobsen's hydrolytic kinetic resolution (HKR) and Grignard reaction as key steps.     

One‐Pot Synthesis of Hydrophobically Modified Iminosugar C‐Alkynylglycosides: Facile Synthesis of Polyhydroxy Tetrahydroindolizines

A mild and efficient one‐pot method has been developed for the stereoselective synthesis of structurally diverse novel iminosugar C‐alkynylglycosides. The generality of this methodology has been demonstrated with a wide variety of amines and copper acetylides. This one‐pot method has been exploited in the synthesis of new class of DNA cross‐linking agents, polyhydroxy 1‐vinyl‐tetrahydroindolizine derivatives.     

Cu(I)‐Catalyzed Efficient Synthesis of 2′‐Triazolo‐nucleoside Conjugates

A small library of thirty‐two 2′‐triazolyl uridine and 2′‐triazolyl‐5‐methyluridine has been synthesized by Cu(I)‐catalyzed condensation of 2′‐azido‐2′‐deoxyuridine and 2′‐azido‐2′‐deoxy‐5‐methyluridine with different alkynes and aryl propargyl ethers in almost quantitative yields. Triazolo‐nucleoside conjugates, which can be evaluated for different biological activity for suitable drug development, were unambiguously identified on the basis of ¹H NMR, ¹³C NMR, IR, and HRMS data analysis. These compounds have been synthesized for the first time and have not been reported in the literature earlier.     

Synthesis of Some Novel Bisisoxazolidine Derivatives from Glyoxal‐derived Bisnitrones via Simultaneous Double Cycloaddition Reactions in Water

Simultaneous double 1,3‐dipolar cycloaddition reactions of glyoxal‐derived bisnitrones have been described in water. Significant rate acceleration and improved yields of exclusively diastereoselective and regioselective bisisoxazolidines in water have been observed at room temperature in a short reaction time compared with conventional solvents.     

EXAFS studies of cobalt oxides and oxide glasses

The exafs of Co²⁺ has been studied in rare earth cobaltites and in sulphate and borate glasses. It has been found that the environment of Co²⁺ ions is very similar in these cases. It appears feasible to study local structures in glasses using probe ion exafs. Communication No. 151 from the Solid State and Structural Chemistry Unit.     

Synthesis and characterization of crosslinked polydiacetylene and its two-component interpenetrating polymer networks

The synthesis of crosslinked polydiacetylenes and its two-component interpenetrating polymer networks (IPNs) was carried out utilizing its polar and flexible substituent groups. Polydiacetylenes were crosslinked by the formation of allophanate linkages utilizing urethane groups in the substituent groups of the polydiacetylenes. Elemental analysis, DSC, TMA, solvent resistance, and IR spectra are presented as evidence for the formation of crosslinked polydiacetylenes. IPNs of polydiacetylenes and an epoxy resin (diglycidyl ether of bisphenol A) were synthesized by using simultaneous and sequential methods of synthesis. A study of phase morphology of the simultaneous and sequential IPNs was carried out using electron microscopy, TMA, and DSC.     

X-ray structure of physiological copper(II)-bis(L-histidinato) complex

The isolation and the X-ray crystal structure of physiological copper(II)-L-histidine complex are reported. The neutral five-coordinate complex shows distorted square pyramidal geometry with bidentate and tridentate L-histidine ligands. The basic character of the pendent imidazole group and H-bonding interactions of bidentate L-histidine ligand are important for copper transport. The unique structural features help explain the origin of its thermodynamic stability and kinetic reactivity in human blood along with the ternary copper(II)-amino acid complexes. The role of L-histidine in interaction with copper(II)-albumin, in cellular uptake of copper, and in treatment of Menkes disease can be studied using these results.     

Volatile constituents of Origanum vulgare L., 'thymol' chemotype: variability in North India during plant ontogeny

Essential oils derived from six different phenophases, namely early vegetative stage, late vegetative stage, early flowering stage, full flowering stage (FFS), late flowering stage and seed shattering stage of Origanum vulgare L. grown in Kumaon region of Uttarakhand, India were investigated by GC and GC-MS. A total of 38 constituents, representing 97.4-99.7% of the total oil composition, were identified. Major components of oils were thymol (40.9-63.4%), p-cymene, (5.1-25.9%), γ-terpinene (1.4-20.1%), bicyclogermacrene (0.2-6.1%), terpinen-4-ol (3.5-5.9%), α-pinene (1.6-3.1%), 1-octen-3-ol (1.4-2.7%), α-terpinene (1.0-2.2%), carvacrol (<0.1-2.1%), β-caryophyllene (0.5-2.0%) and β-myrcene (1.2-1.9%). Thymol, terpinen-4-ol, 3-octanol, α-pinene, β-pinene, 1,8-cineole, α-cubebene and (E)-β-ocimene were observed to be higher during FFS. The study showed that plant stage had a significant effect on the essential oil content and composition of O. vulgare grown in the hilly tracks of Northern India.     

Luminescence properties of Tb(3+)-doped CaMoO(4) nanoparticles: annealing effect, polar medium dispersible, polymer film and core-shell formation

Tb(3+)-doped CaMoO(4) (Tb(3+) = 1, 3, 5, 7, 10, 15 and 20 atom%) core and core-shell nanoparticles have been prepared by urea hydrolysis in ethylene glycol (EG) as capping agent as well as reaction medium at low temperature ～150 °C. As-prepared samples were annealed at 500 and 900 °C for 4 h to eliminate unwanted hydrocarbons and/or H(2)O present in the sample and to improve crystallinity. The synthesised nanophosphors show tetragonal phase structure. The crystallite size of as-prepared sample is found to be ～18 nm. The luminescence intensity of the (5)D(4) → (7)F(5) transition at 547 nm of Tb(3+) is much higher than that of the (5)D(4) → (7)F(6) transition at 492 nm. 900 °C annealed samples show the highest luminescence intensity. The intensity ratio R (I[(5)D(4) → (7)F(6)]/I[(5)D(4) → (7)F(5)]) lies between 0.3-0.6 for as-prepared, 500 and 900 °C annealed samples. The luminescence decay of (5)D(4) level under 355 nm excitation shows biexponential behaviour indicating availability of Tb(3+) ions on surface and core regions of particle; whereas, contribution of Mo-O charge transfer to lifetime is obtained under 250 nm excitation. The CIE coordinates of as-prepared, 500 and 900 °C annealed 5 atom% Tb(3+)-doped CaMoO(4) samples under 250 nm excitation are (0.28, 0.32), (0.22, 0.28) and (0.25, 0.52), respectively. The dispersed particles in polar medium and its polymer film show green light emission. The luminescence intensity is improved significantly after core-shell formation due to extent of decrease of non-radiative rates arising from surface dangling bonds and capping agent. Quantum yields of as-prepared samples of 1, 5 and 7 atom% Tb(3+)-doped CaMoO(4) samples are found to be 10, 3 and 2, respectively.