A DFT study of the hydrolysis of hydantoin

Density functional theory (DFT) calculations were made on the hydrolysis of hydantoin (2,4-imidazolidinedione). In the neutral hydrolysis, reacting systems composed of hydantoin and (H₂O)_n with n = 1+3, 2+3, 3+3, and 4+3 were adopted. Three water molecules (“+3”) participate in the in-plane hydrogen-bond circuit, and the n–3 = 1, 2, 3 or 4 water cluster works for the out-of-plane nucleophilic attack onto the carbonyl carbon of hydantoin. Transition states (TSs) involving bond interchanges prompted by proton transfers were determined. The reaction path with n = 3+3 containing N-carbamoyl glycine, N-carboxy glycine and three tetrahedral intermediates was found to be most likely. In the acid-catalyzed hydrolysis, a reacting system composed of hydantoin and H₃O⁺(H₂O)₇ was employed. Ten TSs and nine intermediates were obtained. N-carbamoyl glycine and N-carboxy glycine were confirmed to be detectable stable species. The product consists of glycine, carbonic acid (not CO₂), NH₄⁺, and (H₂O)₅. It has the exothermic energy, whereas the product in the neutral hydrolysis is of the endothermic one for all n values. For both neutral (n = 3+3) and acid-catalyzed hydrolyses, the rate-determining steps were calculated to be for formation of the tetrahedral intermediate, HOOC-CH₂-NH-C(OH)₂NH₂. The pattern of proton transfers along hydrogen bonds was carefully investigated.     

Morphosynthesis of poly[4‐(1,4‐phenylene)oxyphthalimide] and copolymers prepared by reaction‐induced crystallization during polymerization

Morphosynthesis of poly[4‐(1,4‐phenylene)oxyphthalimide] (POPI) and poly[4‐(1,4‐phenylene)oxyphthalimide‐co‐4‐phthalimide] (POPI‐PPI) was examined by using the crystallization during the polymerization. The POPI fibrillar crystals were obtained as precipitates with the formation of spherical aggregates of plate‐like crystals. Some of the POPI fibrillar crystals were longer than 15 μm. They possessed high crystallinity and the molecules aligned perpendicular to the long direction of the fibers. On the other hand, one‐dimensional structures of POPI‐PPI such as ribbon, cone, rod, and fiber were obtained as precipitates by the copolymerization. The copolymer molecules might align along the long direction of the cone‐like crystals. The morphology of these poly(ether‐imide)s could be controlled by not only the polymerization condition but also with the aid of copolymerization. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Quadrature Frequency Conversion Scheme Using CsLiB6O10 Crystals for the Efficient Second-Harmonic Generation of High Power Nd:YAG Laser

The ability of CsLiB_6O10 (CLBO) crystals for high power second-harmonic generation (SHG) of a 1064-nm Nd:YAG laser in a quadrature arrangement was experimentally demonstrated. A 532-nm second harmonic output pulse energy of 2.25 J was obtained with 3.21 J of an input 1064-nm fundamental pulse energy at a repetition rate of 10 Hz, corresponding to a power conversion efficiency in excess of 70%.     

Influence of Groove on Metal Vapour Behavior and Arc Characteristics in TIG Welding of High Manganese Stainless Steels

Plasma Chemistry and Plasma Processing - In arc welding, a groove is often used between metal pieces being welded. In tungsten inert gas welding of high-manganese stainless steels with arc voltage...     

Catalytic asymmetric desymmetrization of meso-diamide derivatives through enantioselective N-allylation with a chiral pi-allyl Pd catalyst: improvement and reversal of the enantioselectivity

In the presence of the Trost ligands-Pd catalysts, N-monoallylation of bis(2,4,6-triisopropylbenzne)sulfonylamides derived from meso-1,2-diamines proceeds with good to excellent enantioselectivity (85-96% ee) to give asymmetric desymmetrization products. Under the same conditions, in the reaction with meso-bistolunesulfonylamide derivatives, reversal of the enantioselectivity is observed.     

Stereoselective conversion of anhydrovinblastine into vinblastine utilizing an anti-vinblastine monoclonal antibody as a chiral mould

Dimeric indole alkaloid, anhydrovinblastine, which can be obtained from catharanthine and vindoline in a high yield, was converted stereoselectively into vinblastine through alternating oxidation-reduction with oxygen and NaBH(3)CN in the presence of anti-vinblastine monoclonal antibody.     

Biologically active glycosides from asteroidea, 42. Isolation and structure of a new biologically active ganglioside molecular species from the starfish Asterina pectinifera

A ganglioside molecular species GP-3 (1) has been obtained from the water-soluble lipid fraction of the chloroform/methanol extract of the starfish Asterina pectinifera. The structure of the ganglioside has been determined on the basis of chemical and spectroscopic evidence. Compound 1 represents new ganglioside molecular species possessing two moles of sialic acids at the inner part of the sugar moiety. Partial hydrolysis by hot water and an enzymatic hydrolysis by means of endoglycoceramidase (EGCase) have proved useful for structure elucidation of the complex oligosaccharide moiety. Moreover, 1 exhibits neuritogenic activity toward the rat pheochromocytoma cell line, PC-12 cells, in the presence of nerve growth factor (NGF).