A threefold superstructure of the anti‐epileptic drug phenytoin sodium as a mixed methanol solvate hydrate

Phenytoin sodium, a salt of 5,5‐diphenylimidazolidine‐2,4‐dione, or phenytoin, is commercially available in various dosage forms for its anti‐epileptic properties to treat and prevent seizures. The title compound, poly[aquatris(μ₃‐4,4‐diphenyl‐2,5‐dioxoimidazolidin‐1‐ido)trimethanoltrisodium(I)], [Na₃(C₁₅H₁₁N₂O₂)₃(CH₄O)₃(H₂O)_1.08]_n, a methanol solvate and hydrate of phenytoin sodium, forms a modulated crystal structure that consists of a supercell made up of three close‐to‐identical repeat units. Each of the basic fragments consists of one phenytoin anion, a sodium cation, and either a methanol, or a methanol and a water molecule coordinated to the sodium ion, yielding a formula unit of Na(C₁₅H₁₁N₂O₂)(CH₃OH)_x(H₂O)_y for each of the three segments (x, y = 0 or 1; x + y = 1 or 2). Modulation along the b axis is introduced due to the presence or absence of water or methanol molecules at sodium and by the alternating torsion angles of one of the two phenytoin phenyl rings. Individual segments within the asymmetric unit are linked by covalent Na—O and Na—N bonds, with each sodium ion coordinated to one anionic amide N atom and three keto O atoms. The Na—N and one of the Na—O bonds connect (C₁₅H₁₁N₂O₂)·Na units along the modulation direction, creating an infinite [(C₁₅H₁₁N₂O₂)·Na] chain that is further stabilized by intramolecular N—H…O hydrogen bonding parallel to [010]. The second Na—O bond connects this chain with a symmetry‐equivalent copy of itself created by a screw‐axis operation, yielding double strands of [(C₁₅H₁₁N₂O₂)·Na] chains. Two of these double strands, propagating in opposite directions, constitute the content of the unit cell. Neighboring double strands are connected with each other to form layers perpendicular to the a axis, tethered together via O—H…O hydrogen bonds involving the water and methanol molecules. In addition to modulation, each of the repeat units also exhibits disorder of the modulated segments. Phenyl rings of each repeat unit are rotationally disordered, and sodium‐coordinated methanol and water molecules are also positionally disordered and/or partially occupied. The solvated structure reported here, while not matching the patterns reported for any of the known forms of phenytoin sodium, does provide a first insight into the complications and complexities involved in resolving the structure of anhydrous phenytoin sodium.     

An Efficient,One-Pot Synthesis of Carbamates from the Corresponding Alcohols Using <Emphasis Type="Italic">Mitsunobu</Emphasis>’s Reagent

Summary. A novel Mitsunobu-based protocol was developed for the synthesis of carbamates from the corresponding alcohols using carbon dioxide and amines in good to excellent yields. This protocol is mild, chemoselective, and efficient compared to other reported methods.     

Operation of a capacitor bank for plasma metal forming

Previously metal forming has been done using electromagnet in pulsed power mode, better known as magneform [1]. Here we will be presenting a different technique for metal forming. We are using water as a medium for this process. By discharging the stored electrical energy of the capacitor bank in water, we are getting the desired result i.e. to form (expand or compress) a wide range of workpiece to the desired shapes. The advantage of this method over conventional method is that it uses low power (negligible running cost). It does not require any post assembly cleaning degreasing and is hence environmentally ‘friendly’.     

Vibrational dynamics and heat capacity in poly(L‐lactic acid)

Poly(L ‐lactic acid) (PLLA) (? CH(CH₃) ? COO? )_n is a biodegradable polymer, which exhibits many applications in the biomedical field and where thermoplastics are employed. A comprehensive study of the normal modes and their dispersion in PLLA using Wilson′s GF matrix method as modified by Higgs is being reported. Assignments of calculated normal modes have been made and characteristic features of dispersion curves are discussed. Heat capacity has been calculated via density‐of‐states using Debye relation in the temperature range 10–250 K, which is in fairly good agreement with the experimental data. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 175–182, 2010     

Random-walk theory for localization

A continuous-time random-walk theory has been developed for Anderson localization. On a continuous time scale random walks are performed along extended (i.e., propagating) and localized (i.e., trap) states. Complete information of disorder is contained in a distribution function called “hopping time distribution function” ψ_nm(t), which gives the probability per unit time for transition from state m to state n in time t. The “stay-put” probability ??(t = ∞), which is the probability to rediscover an excitation at a site “0” at time t = ∞ if it was there at t = 0, is obtained in terms of ψ_nm(t). Appropriate forms for ψ_nm(t) are constructed which are in conformity with the photoconductivity experiments on dispersive transport, and ??(∞) are calculated. The results indicate that the entire spectrum consists of three regimes, namely, those of (i) “diffusion,” (ii) “weak diffusion,” and (iii) “no diffusion,” which, respectively, designate the extension, the power-law localization, and the exponential localization of states. The results also shed light on the question of “continuous or discontinuous (?)” transition across the mobility edge.     

The biosynthesis of nornuciferine-I(2-methoxy-6aα-aporphine-1-ol)

The incorporation of (±)-norcoclaurine, (±)-coclaurine, (±)-N-methylcoclairine, (±)-N-methylnorcoclaurine into nornuciferine-I in Croton sparsiflorus morong has been studied, and the specific utilization of the (±)-N-methylcoclaurine demonstrated. The evidence supports the direct oxidative coupling of (+)-(S)-N-methylcoclaurine to give N-methylcrotsparine, which in turn is shown to be a specific precursor of nornuciferine-I. The experiments also show that N-methylcrotsparine is reduced to N-methylcrotsparinol and it is N-methylcrotsparinol-I which is preferentially dehydrated and rearranged to nornuciferine-I.