A short synthesis of (+) and (−)-falcarinol

A short, practical synthesis of the bis-acetylenic natural product falcarinol 1 is reported. This method relies on the alternate functionalisation of bis-trimethylsilylbutadiyne 10. This may be achieved in one-pot, however, better yields were obtained more conventionally. Lipase mediated enzymatic kinetic resolution of the racemic adduct in an organic solvent afforded (+)-1 in 97% enantiomeric excess. The analogous process performed with racemic 3-acetoxy falcarinol 11 under aqueous conditions gave (−)-1. Oxidation of 1 with Dess-Martin periodinane gave falcarinone 2.     

Thermodynamic and optical studies of some ethylene glycol ethers in aqueous solutions at T = 298.15 K

Experimental results of density (ρ), speed of sound (u), and refractive index (n_D) have been obtained for aqueous solutions of ethylene glycol monomethyl ether (EGMME), ethylene glycol monoethyl ether (EGMEE), diethylene glycol monomethyl ether (DEGMME), and diethylene glycol monoethyl ether (DEGMEE) over the entire concentration range at T = 298.15 K. From these measurements, the derived parameters, apparent molar volume of solute (?_V), excess molar volume (V^E), isentropic compressibility of solution (β_S), apparent molar isentropic compressibility of solute (?_KS), deviation in isentropic compressibility (Δβ_S), molar refraction [R]_1,2 and deviation in refractive index of solution (Δn_D) have been calculated. The Redlich–Kister equation has been fitted to the calculated values of V^E, Δβ_S and Δn_D for the solution. The results obtained are interpreted in terms of hydrogen bonding and various interactions among solute and solvent molecules.     

Global Minimum‐Energy Structure and Spectroscopic Properties of I2.−⋅n H2O Clusters: A Monte Carlo Simulated Annealing Study

The vibrational (IR and Raman) and photoelectron spectral properties of hydrated iodine‐dimer radical‐anion clusters, I₂^.? ? n H₂O (n=1–10), are presented. Several initial guess structures are considered for each size of cluster to locate the global minimum‐energy structure by applying a Monte Carlo simulated annealing procedure including spin–orbit interaction. In the Raman spectrum, hydration reduces the intensity of the I? I stretching band but enhances the intensity of the O? H stretching band of water. Raman spectra of more highly hydrated clusters appear to be simpler than the corresponding IR spectra. Vibrational bands due to simultaneous stretching vibrations of O? H bonds in a cyclic water network are observed for I₂^.? ? n H₂O clusters with n≥3. The vertical detachment energy (VDE) profile shows stepwise saturation that indicates closing of the geometrical shell in the hydrated clusters on addition of every four water molecules. The calculated VDE of finite‐size small hydrated clusters is extrapolated to evaluate the bulk VDE value of I₂^.? in aqueous solution as 7.6 eV at the CCSD(T) level of theory. Structure and spectroscopic properties of these hydrated clusters are compared with those of hydrated clusters of Cl₂^.? and Br₂^.?.     

Stereoselective functionalization of the 1'-position of 4'-thionucleosides

Stereoselective synthesis of novel 1'-alpha-substituted-4'-thionucleosides was achieved starting from D-gulonic acid gamma-lactone via stereoselective nucleophilic substitution.     

Synthesis of pentahydroxy indolizidine alkaloids using ring closing metathesis: attempts to find the correct structure of uniflorine A

Ring closing metathesis of d-glucose derived diene-substrate containing nitrogen functionality followed by asymmetric dihydroxylation afforded sugar substituted dihydroxylated pyrrolidines 8a-c which on 1,2-acetonide deprotection and reductive amination afforded putative uniflorine A 2a and its analogues 2b-c, respectively.     

Rhodium(I) carbonyl complexes of mono selenium functionalized bis(diphenylphosphino)methane and bis(diphenylphosphino)amine chelating ligands and their catalytic carbonylation activity

The chelate complexes of the types (1) and (2) have been synthesized and characterized by IR and NMR spectroscopy. The lower shift of the ν(P-Se) bands and downfield shift of the ³¹P-{¹H}NMR signals for both P(III) and P(V) atoms in 1 and 2 compared to the corresponding free ligands indicate chelate formation through selenium donor. 1 and 2 show terminal ν(CO) bands at 1977 and 1981 cm⁻¹, respectively, suggesting high electron density at the metal center. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. The rhodium atom is at the center of a square planar geometry having the phosphorus and selenium atoms of the chelating ligand at cis-position, one carbonyl group trans- to selenium and one chlorine atom trans- to phosphorus atom. 1 and 2 undergo oxidative addition (OA) reaction with CH₃I to produce acyl complexes (3) and (4), respectively. The kinetics of the OA reactions reveal that 1 undergoes faster reaction by about 4.5 times than 2. The catalytic activity of 1 and 2 in carbonylation of methanol was higher than that of the well known species [Rh(CO)₂I₂]⁻ and 2 shows higher catalytic activity compared to 1.